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1999 Polaris Service Manual

1. Troubleshooting Tips 0 1 4 Throttle e Pilot air screw misadjusted e Pilot jet of wrong size loose or obstructed e Obstruction of pilot jet e Pilot jet loose e Choke plunger not seating rich e Carburetor mounting air leak lean e Crankshaft seal air leak lean Fuel pump diaphragm damaged rich e Float level incorrect e Air bleed obstructed Polaris Industries Inc 4 49 10 98 FUEL SYSTEM CARBURETION Troubleshooting Troubleshooting Tips 1 4 3 8 Throttle Obstruction in main jet or needle jet Jet needle worn or out of adjustment Pilot system malfunction Incorrect throttle valve cutaway Troubleshooting Tips 3 8 3 4 Throttle Main jet incorrect size or clogged lean Needle jet damaged or loose Needle jet jet needle worn rich E clip position incorrect for altitude and temperature Troubleshooting Tips Full Throttle 10 98 Main jet size rich or lean Fuel filter blocked lean Fuel vent lines or check valves plugged Exhaust system plugged Air box restricted Fuel pump weak Exhaust leaking into engine compartment rich Water in float bowl lean 4 50 Polaris Industries Inc
2. Adjustment Screw LE Ring AB 4 Lever SL oe f de amp Plate Plate Packing Beet d A Cap H V E Ring P 2 9 guias JNS Spring P Pilot Jet l ut ilot Je 3 Holder Piston Valve a Manap E dde Jet 1 Spring Jet Needle P o N i Be Float Needle amp Be P eo Ee Seat Asm ESTA Drain Plug S Polaris Industries Inc 4 5 10 98 FUEL SYSTEM CARBURETION Exploded View Keihin be S Adjuster pum Lock Nut Gasket O LEE Ng S Spring Seat a Retainer Jet Needle a E Clip Enricher Choke Fugen nn P2 Vent SQ Float Pin Idle Adjustment S HL es Screw Ai S ec AGH Main Jet we ee Ze jJ e Inlet Needle Air Screw d Float Drain Plug 10 98 Polaris Industries Inc FUEL SYSTEM CARBURETION Exploded View VM30SS Mixing Chamber Top Including Gasket Throttle Spring Plunger Cap Throttle Plate gt E Ring Jet Needle I Spring s d Plunger 7 g D S lt 2 d Throttle Adjuster Spring Throttle Stop Screw Pilot Jet Main Jet Drain Plug Polaris Industries Inc 4 7 10 98 FUEL SYSTEM CARBURETION Exploded View VM34SS Mixing Chamber Top Including Gasket 2 Plunger Cap Throttle Plate TE Plunger Spring Eng Jet Needle 8 Throttle Valve a Plunger Needle Jet 3 Ed bn p d by Spring SS SS Pe Screw Plate V NY VR N 2 Spring Float Arm Packing se Stop Screw Float PRA ps gt Ring Ne
3. at Crankcase NOTE 1999 500 XC and 500 XC SP fuel filters are inside the fuel tank To inspect replace filter Remove fuel from tank Remove air box e Remove fuel line fitting from fuel tank e Pull fuel line pickup and filter from tank Polaris Industries Inc 4 15 10 98 Carb Mounts FUEL SYSTEM CARBURETION Typical Mikuni Starter System Closed Throttle Mikuni carburetors use a starter enricher system rather than a choke In this type of carburetor fuel and air for starting the engine are metered with entirely independent jets The fuel metered in the starter jet is mixed with air and is broken into tiny particles in the emulsion tube The mixture then flows into the plunger area mixes again with air coming from the air intake port for starting and is delivered to the engine through the fuel discharge nozzle in the optimum air fuel ratio The starter is opened and closed by means of the starter plunger The starter type carburetor is constructed to utilize the negative pressure of the inlet pipe so it is important that the throttle valve is closed when starting the engine Cable Adjuster Lock Nut Plunger Spring IN Plunger Cap Throttle Valve Starter Plunger Inlet Starter ir P r Starter Jet 10 98 4 16 Polaris Industries Inc FUEL SYSTEM CARBURETION Pilot System 0 3 8 Throttle The pilot system s main function is to meter fuel at idle and low speed driving Though its mai
4. 13 1 34 a 14 would be 1 45 The larger the number z the steeper the taper A steeper taper is richer than a shallow taper An R 1470G needle would be richer in the 1 2 to 3 4 throttle range than a R 1370G needle 70 Diameter of the straight portion of the needle see point D A larger diameter needle at point D would be leaner in the 1 8 to 1 4 throttle range than a needle with a smaller diameter at point D A R 1368G has a diameter of 2 685mm at point D A R 1370G has a diameter of 2 705mm at point D G The length from the top of the needle to a point on the taper that is 2 515mm in diameter A Q is shorter than a J This length mainly affects mixture in the 1 4 to 1 2 throttle range A R 1370G is shorter at L1 than a R 1370J and a R 1370G is richer in the 1 4 to 1 2 throttle range than a R 1370J Polaris Industries Inc 4 23 10 98 FUEL SYSTEM CARBURETION Mikuni VM Carburetor Service Wear eye protection when using compressed air or cleaning solvents Review all fuel system warnings found on page 4 1 before proceeding Carburetor Removal Disassembly and Inspection Typical VM Mikuni 1 Remove carburetor from engine Before disassembling clean outside of carburetor thoroughly with solvent _ CAUTION Do not use compressed air to dry at this time The float chamber could become pressurized resulting in damage to the floats or inlet needle and seat 2 Remove slide valve
5. tions 10 98 4 48 Polaris Industries Inc FUEL SYSTEM CARBURETION Troubleshooting Fuel system diagnosis should follow a specific path first examining the fuel tank then the filters fuel lines vent lines fuel pump impulse hose air box exhaust system and finally the carburetors The following troubleshooting information assumes that the general mechanical condition of the engine pistons rings bearings etc is good When the fuel air mixture is diagnosed as improper due to spark plug readings clean the carburetor and blow its passages clear with compressed air Use the spark plug firing end condition as a guide for further determination of whether the mixture is too rich or too lean Use the throttle lever to determine at what degree of throttle valve opening the problem exists CONDITION SYMPTOMS Mixture Too Rich Black spark plug tip plug fouling Heavy exhaust smoke Engine runs worse after warm up Engine loads up Mixture Too Lean Spark plug electrodes white Fluctuation in engine speed Power loss Engine overheats Cylinder scoring Holing pistons Backfiring detonation Throttle diagnostic opening check points Poor Fuel Mileage Incorrect ignition timing Improper track tension too tight Incorrect carburetor jetting Fuel leaks lines fittings fuel pump Needle and seat leaks Plugged exhaust Carburetor vent line problems Clutching incorrect for conditions worn belt
6. 11 10 98 FUEL SYSTEM CARBURETION ACCS System Altitude Compensating Carburetor System ACCS The Altitude Compensating Carburetor System ACCS is designed to automatically compensate for changes in altitude This allows the snowmobile to operate in changing elevations without having to change jets although extreme temperatures may require re jetting for optimum performance Refer to the jetting compensation chart in the specifications sections A vacuum line is connected to the float bowl The ACCS valve is connected to this line via the 4 way manifold At low altitude the ACCS valve supplies atmospheric pressure to the vacuum line and the float bow see Ill 1 At high altitudes the bellows expand moving the plunger to the left and closing off some of the passageways through the ACCS valve see Ill 2 This prevents atmospheric pres sure from reaching the float bowl allowing the vacuum line to reduce the pressure in the float bowl This reduces the amount of fuel sup plied through the carburetor preventing the mixture from becoming too rich NOTE The ACCS valve is calibrated specifi cally for the model it was intended There are no adjustments for the valve and it should not be tampered with in any way 10 98 High Atmospheric Pressure e Bellows compress e Fuel flow increases Vacuum from Venturi To Float Bowls Sealed Bellows Low Altitude High Atmospheric Pressure ACCS
7. 2 5 500 Classic 3 247 Indy 500 RMK EC5OPL162 VM34SS 2 Zinc 260 11 4 6FJ43 P 0 2 5 1 ACCS 3 480 Indy Classic Trng EC50PL192 VM34SS 2 Zinc 250 35 3 4 6EJ26 P 2 43 480 Indy XLT SP EC58PL160 TM 38 3 11 2 9DH3 54 Sod M RA 3 Indy XLT Classic EC58PL131 VM34SS 3 AL 250 40 1 6DP17 Q 4 2 5 1 2 480 XLT Touring EC58PL131 VM34SS 3 Zinc 250 40 1 6DP17 Q 4 2 5 2 480 3 Indy 600 XC SP SN60 70 99A2 Keihin PWK 39 2 38 1 R1368G 2 AL 3 FIXED a E PESE Indy 700 XC SP SN70 70 99A2 Keihin PWK 39 2 PTO 185 38 R1368G MAG 190 3 FIXED Indy 600 RMK SN60 70 99A1 Keihin PWK 39 2 185 1 R1367G ACCS 2 FIXED Indy 700 RMK SN70 70 99A3 Keihin PWK 39 2 48 R1368G 2 ACCS 2 FIXED Indy 700 SKS SN70 70 99A1 Keihin PWK 39 2 PTO 185 38 R1368G 5 5 2 ACCS MAG 190 3 FIXED Indy WideTrak LX EC50PL202 VM34SS 2 Zinc 195 1 2 6EJ26 P 6 2 166 Indy 700 XCR EC70PLO11 TM 38 3 430 1 5 9CG1 54 P 4 3 3 825 Indy 800 XCR EC79PLO11 TM 38 3 450 9DH6 54 P 4 2 0 3 3 825 Fuel Requirements All 1999 models 87 non oxygenated or 89 oxygenated Float Levels 1 With carburetor inverted and float bowl removed float arm must be parallel with float bowl gasket mating surface 2 Use Keihin float level gauge tool PN 2872126 to achieve 16mm float height 3 Floats are not adjustable on Mikuni TM 38 carburetors 10 98 4 4 Polaris Industries Inc FUEL SYSTEM CARBURETION Exploded View Mikuni TM 38 H Top Cap e O
8. Carburetor Assembly 1 Install pilot jet and main jet 2 Install inlet needle and float assembly sisi iii 3 Hold carburetor at angle shown so needle spring is not compressed Measure from gasket surface of carb body to highest point on float Measurement should be within specification Float Height Keihin 16mm 2 mm Float Level Guage PN 2872126 4 To adjust float level bend tang contacting inlet needle See photo above CAUTION Do not bend float arm Adjustment should be made with tang contacting inlet needle Polaris Industries Inc 4 31 10 98 FUEL SYSTEM CARBURETION Keihin Carburetor Service Leak Testing Needle and Seat 1 After adjusting float level place carburetor in an inverted position 2 Connect pressure tester to fuel inlet fitting Apply 5 psi pressure and observe for one minute The needle and seat should hold pressure indefinitely If the pressure drops carefully inspect the needle and the needle seat The needle can be replaced if necessary The needle seat cannot be replaced If the seat surface is damaged replace the carburetor Pressure Tester PN 2870975 3 Carefully inspect float bowl gasket and replace if necessary Install float bowl on carburetor 4 Install idle screw and air adjusting screw 5 Install jet needle E clip into correct groove on needle jet 6 Install jet needle into throttle valve 7 Screw cable holder into throttle valve to secu
9. Inspect for nicks or burrs which may cause sticking Cap i Gaskett __ D 3 Remove jet needle by compressing return spring 25 toward top cap and removing throttle plate which rests Spring on top of needle E clip Note the E clip position and e inspect needle taper for wear An indication of wear Retainer Plate would be an hourglass shape or polished spots No Clip aD Jet Needle somewhere along the taper e Slide Valve EI 4 Remove enricher choke plunger Check condition of seal on tip of plunger Any nicks or cuts will cause leakage and a rich fuel condition usually most evident at idle and low speeds Inspect the plunger seat for damage or foreign material 5 Check choke cable movement Plungers and springs should move back and forth freely without binding Plunger Seat 10 98 4 24 Polaris Industries Inc Carburetor Disassembly and Inspection 6 Remove water trap assembly from float bowl and inspect O ring hose and clamp condition Refer to exploded view corresponding with carburetor being serviced 7 nspect enricher choke fuel supply passage in bowl for obstruction 8 Use an automatic center punch to remove float arm pin Remove inlet needle and seat assembly 9 Inspect needle for wear and replace sealing washers upon reassembly Do not bend float arm during disassembly Do not use exces sive force to remove float arm pin The float pin tower cast ings are very easily damaged and are no
10. System Low Atmospheric Pressure e Bellows expand e Fuel flow decreases Vacuum from Venturi To Float Bowls Sealed Bellows High Altitude Low Atmospheric Pressure ACCS System 4 12 Polaris Industries Inc FUEL SYSTEM CARBURETION Gasoline Volatility Explanation of Gasoline Volatility One of the sometimes misunderstood properties of gasoline is its volatility or ability to vaporize at different ambi ent temperatures and altitudes during the year When gasoline is blended it is given a Reid Vapor Pressure RVP number which reflects its ability to vaporize or mix with air at a given temperature range Gasoline vapor pressure is measured by putting a sample of fuel inside a closed container and applying a specified amount of heat to the container for a certain amount of time RVP will vary from about 7 0 PSI during the summer to approximately 13 5 PSI during the colder months Service stations selling a large volume of fuel will normally have the correct blend to work well at all times throughout the year in their local area When the weather is very cold gasoline must be able to vaporize very quickly in order for an engine to start and warm up properly If summer blend fuel is being used in the winter little or no vaporization will occur Droplets will form causing flooding and very hard starting If winter blend fuel is being used during the summer months it may cause vapor lock boiling fuel inside the fue
11. at idle and low speeds Inspect the plunger seat for damage or foreign material 5 Check enricher choke cable movement Plungers and springs should move back and forth freely without binding 10 98 4 28 Plunger Seat Polaris Industries Inc Disassembly Cont 6 Remove water trap assembly from float bowl and inspect O ring hose and clamp condition Refer to exploded view corresponding with carburetor being serviced 7 Inspect choke fuel supply passage as shown for obstruction 8 Remove float arm pin Remove inlet needle NOTE Seat assembly is not replaceable DO NOT remove 9 Inspect needle for wear CAUTION Do not bend float arm during disassembly Do not use exces sive force to remove float arm pin The float pin tower cast ings are very easily damaged and are not repairable Polaris Industries Inc 4 29 FUEL SYSTEM CARBURETION Keihin Carburetor Service m Trap Nut r1 T Clamp Drain Plug T 17 10 98 FUEL SYSTEM CARBURETION Keihin Carburetor Service Carburetor Disassembly Cont 10 Remove main jet 11 Remove pilot jet 12 Remove pilot air screw and clean all passages in the carburetor body with carburetor cleaner Dry all passages and jets with compressed air Replace gaskets and any parts which show wear or damage 10 98 4 30 Polaris Industries Inc FUEL SYSTEM CARBURETION Keihin Carburetor Service
12. etas 3130100 TEEN 3130129 142 3050235 142 90 ED 3130101 2104 ceres 3130130 CH 3050235 145 EE 3130102 280 en 3130131 1487 5 3050235 148 100 3130103 EEN 3130132 150 Me 3050235 150 105 sd 3130104 300 si ele en 3130133 EE 3050235 152 MO 3130105 310 socer 3130134 155 3050235 155 VAD end eg 3130106 A NR RE 3130135 158 i sss 3050235 158 EINEN 3130107 330 5 c A 3130136 160 3050235 160 EIER 3130108 340 ee 3130137 162 eos 3050235 162 d n ele eve 3130109 EE 3130138 CR 3050235 165 135 EE 3130110 360 reni 3130139 CH 3050235 168 IER 3130111 ST 3130290 3705 res 3050235 170 145 esses 3130112 380 sss 3130140 172 s 3050235 172 In 3130113 390 nee 3130480 176 3050235 176 155 nn 3130114 400 5 es ehe 3130141 178 257 3050235 178 160 hs 3130115 CES 3130599 180 e 3050235 180 165 nn 3130116 ABO nz 3130142 182 sus 3050235 182 Wr 3130117 EE 3130143 185 3050235 185 TE en 3130118 SE co N 3130144 188 ius 3050235 188 E BEE 3130119 450 Ae AA 3130145 190 Seren 3050235 190 STEEN 3130120 TER 3130146 192 ern 3050235 192 1905 stus 3130121 B70 NN 3130147 ER 3050235 195 195 een 3130122 490 esses 3130148 198 seus 3050235 198 GO stored 3130123 500 been 3130149 200 3050235 200 MO 3130124 En 3130150 ops 3050235 205 NEE 3130125 E 3130151 e WEE 3050235 210 Fr RENNER 3130126 E 3130152 EE 3050235 215 EE 3130127 en 3130153 200 3050235 220 Polaris Industries Inc 4 1 10 98 F
13. under controlled conditions Larger numbers give a greater flow resulting in a richer mixture Main jets are screwed directly into the needle jet base y Keihin Main Jet The number on the Keihin main jet corresponds to the diameter of the metering orifice Jetting Guidelines Changes in altitude and temperature affect air density which is essentially the amount of oxygen available for combustion In low elevations and cold temperatures the air has more oxygen In higher elevations and higher temperatures the air is less dense Carburetors on most Polaris models are calibrated for an altitude of 0 3000 ft 0 900 meters and ambient temper atures between 20 to 410 F 29 to 12 C All carburetors must be re calibrated if operated outside the pro duction temperature and or altitude range The main jet installed in production is not correct for all altitudes and or temperatures A main jet that is too small will cause a lean operating condition and may cause serious engine damage Jet the carburetors carefully for elevation and temperature according to the jetting charts in this manual or the jetting charts in the Owner s Safety and Maintenance Manual for each particular model NOTE It is the owner s responsibility to ensure that the correct jets are installed in the machine for a geographical area Be very careful when jetting down in warm weather As the weather turns colder it will be necessary to re jet upward to prevent e
14. valves must be care fully examined for cracks holes or other dam age If in doubt as to the condition of any internal parts replace all diaphragms check valves and gaskets Polaris Industries Inc 4 43 10 98 FUEL SYSTEM CARBURETION Exploded View Fuel Pump Taio Giken Description of Parts 1 Vacuum from crankcase 2 Diaphragm 3 Gaskets 4 Check Valves 5 Fuel Outlets to carbs 6 Fuel Inlet from tank 10 98 4 44 Polaris Industries Inc FUEL SYSTEM CARBURETION Exploded View Twin Cylinder Typical Fuel Pump Parts Description 1 Pump Body Assembly 2 Lower Gasket 3 Diaphragm 4 Upper Gasket 5 Screw 6 used 6 Check Valve Polaris Industries Inc 4 45 10 98 FUEL SYSTEM CARBURETION Exploded View 3 Cylinder Fuel Pump Parts Description 1 Pump Valve Body 2 Diaphragms and Gaskets 3 Screw 6 used 4 Check Valves NOTE Be sure of proper order and position of gaskets and diaphragms upon reassembly 5 Fuel Outlet 3 to carbs 6 Fuel Inlet from tank 7 Vacuum Pressure from crank case 10 98 4 46 Polaris Industries Inc Polaris Industries Inc FUEL SYSTEM CARBURETION Exploded View Twin Cylinder Domestic Fuel Pump 4 47 Walbro Fuel Pump NOTE Individual parts are not available for do mestic engine fuel pumps If any internal parts are faulty the pump must be replaced 10 98 FUEL SYSTEM CARBURETION Water Tr
15. 50221 R 4371J EEE 3050246 NEEDLE JET NO PART NO P 6 247 ns 3130655 P 8 247 oisi ee 3130382 Q 0 247 ccu tede ech 3130414 Q 2 247 tuo id stel 8130165 Q 4 247 Cos eet tet 3130603 Q 8 247 22 3130485 R 0 247 eebe e cus 3130477 P 0 286 3130607 P 2 286 ann 3130608 O 4 286 2 2222 3130635 O 6 480 3130429 O8 480 cereus 3130683 P 2 480 aaien 3130675 P 4 480 sss 3130639 Q 6 480 iiie vis 3130618 P 8 513 3130510 Throttle Valve No PART NO SO AL Vis 3050234 B02 Aland 3050234 C02 ro RAP NON 3050234 D02 LIMEN 3050234 J02 One 3050234 E02 EE 3050234 K02 T EE 3050234 F02 Teen 3050234 L02 BO ee ere 3050234 G02 D ENEE 3050234 H02 10 98 42 Polaris Industries Inc FUEL SYSTEM CARBURETION Mikuni TM 38 Jet Part Numbers DESCRIPTION PARTNUMBER DESCRIPTION Jet Needle J8 9DH01 54 3130706 Pilot Air Jet 1 5 3130783 Jet Needle J8 9CJB01 50 3130797 Pilot Air Jet 6 3130784 Needle Jets ss Pilot Air Jet 1 7 3130785 Needle Jet 08 3130798 Pilot Air Jet 1 8 3130786 Needle Jet P 3130799 Pilot Air Jet 1 9 3130787 3130781 3130782 8 0 Pilot Air Jet 2 0 3130788 6 8 0 Piston Valves Slides Piston Valve 1 5 3130940 P P Piston Valve 2 0 3130789 Piston Valve 2 5 3130790 Co PsenVawe Soja Sarerjs 190 soos Psonvave Blasen aeris Ire Pistonvawe 40 si
16. 975 4 Apply approximately 5 PSI pressure and wait for one minute The needle and seat should hold pressure indefinitely If the pressure drops rapidly replace the needle and seat assembly and or sealing washers Polaris Industries Inc 4 27 FUEL SYSTEM CARBURETION Mikuni VM Carburetor Adjustments 10 98 FUEL SYSTEM CARBURETION Keihin Carburetor Service Wear eye protection when using compressed air or cleaning solvents Review all fuel system warnings found on page 4 1 before proceeding Carburetor Removal Disassembly and Inspection 1 Remove carburetor from engine Before disassembling clean outside of carburetor thoroughly with solvent CAUTION Do not use compressed air to dry at this time The float chamber could become pressurized resulting in damage to the floats or inlet needle and seat Do not soak Keihin car buretors in carb cleaner Clean only with aerosol cleaner 2 Remove slide valve Inspect for nicks or burrs which may cause sticking 3 Remove jet needle by compressing return spring toward top cap and removing throttle cable Disconnect cable holder and remove jet needle Note E clip position and inspect needle taper for wear An indication of wear would be an hourglass shape or polished spots somewhere along the taper 4 Remove enricher choke plunger Check condition of seal on tip of plunger Any nicks or cuts will cause leakage and a rich fuel condition usually most evident
17. CHAPTER 4 FUEL SYSTEM CARBURETION Jet Part Numbers soso tak 2er 4 1 4 3 1999 Condensed Data Lsue 4 4 Exploded View M28 4 5 Exploded View kein 4 6 Exploded View VM30SS sss 4 7 Exploded View VM34SS ss 4 8 Exploded View VM38SS een 4 9 Exploded View VM34SS with ACCS 4 10 Exploded View Keihin with ACCS 4 11 ACCS SYSIGIN sos rame eee rS CV EE has 4 12 Gasoline Volatility ooo de mor e 4 13 SNE ETS etu tob P E E PEE tad bns 4 14 4 15 Component Functions 002s eee e eee 4 16 4 21 Component Effect vs Throttle Opening 4 22 Keihin Needle Explanation 4 23 Mikuni VM Carburetor Service 4 24 4 27 Keihin Carburetor Service 6 4 28 4 33 Mikuni TM 38 Carburetor Service 4 34 4 38 Mikuni TM 38 Synchronization Procedure 4 39 4 40 Carburetor Adjustments 4 41 Primer Systems 4 42 Fuel Pump Operation 32 dete Pec TUERI 4 43 Exploded View Fuel Pumps 4 44 4 47 Water Trap Service iiss vk EN STEE Re hr VE 4 48 Troubleshooting ees ccr aoa eee kare ee d 4 49 4 50 FUEL SYSTEM CARBURETION Jet Part Numbers Whenever servicing the carburetor or fuel system it is important to heed the following warnings A WARNING Gasoline is extremely flammable and explosive under certain conditions Always stop th
18. UEL SYSTEM CARBURETION Jet Part Numbers Jet Needle Part Numbers Mikuni JET NEEDLE NO PART NO BDPT7 s s 3130155 5DT49 3130154 5DP10 55 een 3130333 5DP10 3130310 DTZ i i 3130473 5D78 3130667 BERT ees 3130528 6CEY6 usse 3130476 6CF1 i255 is 3130725 6CGY3 3130484 6CGY6 3130652 6DH3 4 2 3130470 Jet Needle Part Numbers Keihin JET NEEDLE NO PART NO R 1368G 3050244 R 1370G 3050220 R 1871G 3050256 R 1372J 3050247 Needle Jet Part Numbers Mikuni NEEDLE JETNO PART NO P 4 159 3130162 P 2 166 3130460 P 4 166 3130348 P 4 166 3130499 P 6 166 3130160 P 8 166 3130421 Q 2 166 3130376 0 4 169 3130166 0 4 169 3130409 O 6 169 3130358 O 6 169 3130469 0 8 169 3130453 Q 8 071 te 3130035 P 0 225 3130579 P 2 255 3130608 P 2 259 3130161 P 0 247 3130671 P 2 247 3130672 P 4 247 3130641 Throttle Valve Part Numbers Keihin JET NEEDLE NO PART NO 6DH4 oo onen 3130402 eg 3130391 ep 3130329 eg 3130645 6DH29 sss 3130462 epp 3130156 6DP17 S oc ees 3130374 EECH 3130423 BEJ3 MM 3130680 L C One 3130319 BER ops 3130378 JET NEEDLE NO PART NO R 13698 3050245 R 1370J i cest oes 30
19. ap Service A WARNING Fuel spillage will occur during this installation Gasoline is extremely flammable and explosive under certain conditions Do not smoke or allow open flames or sparks in or near the area where refueling is performed or where 8 gasoline is stored Do not weld or operate a torch near the fuel system Remove fuel tank before any chassis welding is per formed If you get gasoline in your eyes or if you swallow gasoline see your doctor immediately If you spill gasoline on your skin or clothing immediately wash it off with soap and water and change clothing Never start the engine or let it run in an enclosed area Gasoline powered engine exhaust fumes are poison ous and can cause loss of consciousness and death in a short time Turn fuel valve off Remove air silencer Position a shop cloth or container below drain plug and water trap plug Remove drain plug and sealing O Ring or slide clamp upward and remove water trap plug Drain water fuel Clean trap with electrical contact cleaner and dry with compressed air Lightly grease O ring and install water trap assembly into bottom of float bowl or reinstall trap plug in hose and position Tighten securely Turn fuel on start engine and check for possible fuel leaks Reinstall air box The water traps should be periodically inspected and drained Draining frequency will depend upon fuel supply riding conditions and fue handling precau
20. ction 1 Remove carburetor rack from engine Before disassembling clean outside of carburetor thoroughly with solvent Do not use compressed air to dry at this time The float chamber could become pressurized resulting in damage to the floats or inlet needle and seat Do not soak carburetors in carb cleaner Clean only with aerosol cleaner 2 Remove top caps 3 Remove four screws on funnel 4 Turn throttle shaft so slide opens all the way NOTE You may have to turn out slide stop screw for slide to move farther up body 5 With slide fully open pull funnel out bottom first 10 98 4 34 Polaris Industries Inc Disassembly Cont 6 From top of carb loosen allen head screw holding needle in position Slide holding plate to side 7 Reach into top of carb with a long nose pliers and pull out needle 8 Inspect needle for wear 9 Remove E rings packing plate spring and rings connecting slide to lever Polaris Industries Inc 4 35 FUEL SYSTEM CARBURETION Mikuni TM 38 Carburetor Service 10 98 FUEL SYSTEM CARBURETION Mikuni TM 38 Carburetor Service Carburetor Disassembly Cont 10 Remove water trap drain plug 17 mm and single screw on bottom of carb 11 Remove float body NOTE Float body will not come off unless water trap drain plug is removed which is threaded and screws into main jet housing 12 Re
21. cy of the float and the fuel pressure of the fuel pump balance the needle valve sticks fast to the needle seat preventing further delivery of gasoline thereby holding the standard level of gasoline The fuel level in the bowl assists in controlling the amount of fuel in the fuel mixture Too high a level allows more fuel than necessary to leave the nozzle enriching the mixture Too low a level re sults in a leaner mixture since not enough fuel leaves the nozzle Therefore the predetermined fuel level should not be changed arbitrarily Polaris Industries Inc FUEL SYSTEM CARBURETION Function Float Guide Pin Needle Valve Float Arm 4 21 10 98 FUEL SYSTEM CARBURETION Component Effect vs Throttle Opening INCREASIN a 71 DECREASING m 0 Ve 14 38 V2 5 8 3 4 8 FULL THROTTLE OPENING TYPICAL MIKUNI VM Se Throttle Valve Cut Away Jet Needle Needle Jet Polaris TM 38 Mikuni component effect versus throttle opening chart needle valve main jet jet needle needle jet throttle valve bypass sion pin outlet air jet choke plunger Start 4 starter jet fuel screw O stat idle 1 4 1 2 3 4 Full Throttle Position 10 98 4 22 Polaris Industries Inc FUEL SYSTEM CARBURETION Keihin Needle Explanation Polaris currently uses Keihin PWK 39 carburetors on some of the domestic engines What follows is an explanation of Keihin jet needle nomenclature NOTE Polaris carbureto
22. e engine and refuel outdoors or in a well ventilated area Do not smoke or allow open flames or sparks in or near the area where refueling is performed or where gasoline is stored or used Do not overfill the tank Do not fill the tank neck If you get gasoline in your eyes or if you swallow gasoline see your doctor immediately If you spill gasoline ori your skin or clothing immediately wash it off with soap and water and change cloth ing gt PPR PB Never start the engine or let it run in an enclosed area Gasoline powered engine exhaust fumes are poi sonous and can cause loss of consciousness and death in a short time Jet Part Numbers The following chart lists main and pilot jets and the part number of each that are presently available Mikuni Mikuni Keihin Keihin PILOT JET NO PART NO PILOT JET NO PART NO PILOT JET PARTNO PILOT JET PART NO P PM NE 3130064 50 3130069 35 5 2 3050219 35 50 3050219 50 Ee 3130065 EC 3130070 38 ous 3050219 38 B2 3050219 52 B5 eren Ei 3130066 60 3130071 40 WEE 3050219 40 55 3050219 55 TEE 3130067 65 3130072 42 3050219 42 58 3050219 58 T COME 3130068 45 22 3050219 45 60 3050219 60 On 3130629 48 71 3050219 48 62 3050219 62 nn 3130070 65 3050219 65 Mikuni Mikuni Keihin E AD HEX HEAD Long Hex Head MAIN JET NO PART NO MAIN JET NO PART NO MAIN JET NO PART N D I 3130099 250 REN 3130128 140 222222 3050235 140 85
23. edle amp r Main Jet SES S Gasket Float Drain Plug 10 98 4 8 Polaris Industries Inc FUEL SYSTEM CARBURETION Exploded View VM38SS Mixing Chamber Top GE Including Gasket Plunger Cap Plunger Spring Jet Needle Plunger Throttle Valve ch a Cap i dd NG Sprin ra LA Screw Plates N it RY Spring Float Arm Age Packing N gt Pilot Throttle Stop Screw Float Pin gt lt NGA Ss Jet Bw b gt 6 Ring Needle amp 4 AA b Main Jet Seat E bl AR Gasket 5 Drain Plug E Polaris Industries Inc 4 9 10 98 FUEL SYSTEM CARBURETION Exploded View VM34SS with ACCS Trail RMK 500 RMK MAG SIDE PTO SIDE Rubber Pipe Tee Fittings C ACCS Valve Markings Trail RMK 500 RMK 50M05 ACCS Valve Do not change calibration settin or serious engine damage may result ACCS valves cannot be interchanged between models When replacing a faulty valve be sure the identification number stamped on the valve body is correct 10 98 4 10 Polaris Industries Inc FUEL SYSTEM CARBURETION Exploded View Keihin Carbs with ACCS 600 RMK 700 RMK ACCS Valve Markings 600 RMK 1253232 700 RMK 1251086 Do not change calibration setting or serious engine damage may result ACCS valves cannot be interchanged between models When replacing a faulty valve be sure the identification number stamped on the valve body is correct Polaris Industries Inc 4
24. edle Jet 3 8 3 4 Throttle Pilot Jet Needle Jet Main Jet 15 50 75 100 Fig 1 Throttle Valve Opening Air Bleed Opening 10 98 FUEL SYSTEM CARBURETION Main System 3 4 to Full Throttle The main system is designed to deliver fuel between low speed and high speed operation This system is made up of the jet needle needle jet and main jet The main system begins to take effect as soon as there is enough air flow into the carburetor venturi to draw fuel up through the main jet and needle jet assembly This system works in conjunction with the needle jet sys tem During low speed driving there is very little clearance between the jet needle and the needle jet therefore very little fuel from the main jet can pass between the jet needle and the needle jet As the throttle valve opening is increased the tapered jet needle is raised farther out of the needle jet allowing greater fuel flow HI Under full throttle opening the cross sectioned area of 5f ME d Pilot Jet clearance between the jet needle and the needle jet E Needle Jet becomes greater than the cross sectioned area of the Main Jet main jet Thus the main jet is now controlling the amount of fuel flow Main Jet When the throttle opening becomes greater and the area between the needle jet and jet needle increases fuel flow is metered by the main jet The number on the jet indicates the amount of fuel CCs which will pass through it in one minute
25. et passage and leans the mixture Letter and number codes are stamped into the needle and the jet indicating sizes and tapers needles only of each Jet Needle Needle Jet Fig 1 The jet needle tapers off at one end and the clearance be tween the jet needle and the needle jet increases as the throttle valve opening gets wider The air fuel mixture ratio is controlled by the height of the E ring inserted into one of the five slots provided in the head of the jet needle The chart at right shows the variation of fuel flow based on the height of the E ring Needle Jet Fig 2 The needle jet works in conjunction with the jet needle to regulate fuel flow rate An air bleed opening in the side of the needle jet brings in air measured by the air jet This air initiates the mixing and atomizing process inside the needle jet Mixing is augmented by a projection at the needle jet outlet called the primary choke The letter number code stamped on the jet indicates jet inside diameter Throttle Opening vs Fuel Flow Fig 3 In a full throttle condition the cross sectioned area be tween the jet needle and the needle jet is larger than the cross sectioned area of the main jet The main jet therefore has greater control over fuel flow Small Medium Large Clearance Clearance Clearance Closed One half Full Throttle Throttle Throttle Fig 3 Polaris Industries Inc 4 19 Fuel flow FUEL SYSTEM CARBURETION Jet Needle Ne
26. ition Full On Contents of Lever Kit P di SS 10 98 FUEL SYSTEM CARBURETION Primer Systems Domestic 600 amp 700 Primer Systems Primer Kit Schematic 46 Supply Line dr Reducer Adaptor qup uM 27 Primer Line 4 D Line 3 16 1 Primer Line f Check Valve Tee Fittin 4 Primer Line PN am Primer Tee Fitting Primer kit part 2871889 1998 Domestic 600 700s 1997 700 SKS and RMK Fuel Inlet Line to Primer Fuel Out to Standard primer routing diagram for 1999 600 700 twins 10 98 4 42 Polaris Industries Inc The fuel pumps on all Polaris engines are basically the same The differences are in the size and location of the pumps Pumps may be mounted to the engine or to the chassis In the two cycle engine the pressure in the crankcase changes with the up and down stroke of the piston The amplitudes of pressure vary according to the RPM and degree of throttle opening Whether idling or at full throttle the pressure built up in the crankcase has enough amplitude to operate the pump When the piston is on the upstroke crankcase pressure in that cylinder becomes less positive The diaphragm in the fuel pump moves toward the engine causing a negative pressure or suc tion in the pump chamber This causes the inlet valve from the fuel supply to open and permits fuel to enter the chamber This same suction causes the outlet valve to the carburetor
27. l lines fue pump or carburetor This will cause warm engine driveability problems and hard starting when warm Sore states are limiting the Reid Vapor number to 9 0 PSI year around to help meet evaporative emissions stan dards Warm Weather Low Vaporization Rate iss Lea um Ce a wer eer mer es ar m Co eos 3wE 399 E sees wr er Add 2 4 F for each 1000 feet above seal level High Vaporization Rate Cold Weather Polaris Industries Inc 4 13 10 98 FUEL SYSTEM CARBURETION Systems Float Chamber Venting Fuel flows through a carburetor by creating a pressure difference between the venturi and the float bowl The greater the pressure difference the greater the fuel flow On some models the float bowl is vented to the handle bars This provides consistent atmospheric pressure for a consistent fuel flow If the vent lines become kinked plugged or exposed to fluctuating pressures under hood the pressure difference will change causing erratic fuel flow Polaris has airbox venting on some models The vent lines are connected to a baffle inside the airbox This pro vides a more consistent pressure difference between the carburetor venturi and the float bowl as the vacuum inside the airbox changes For example if the airbox foam filter becomes restricted with snow when riding in pow der the airbox vacuum increases Without airbox venting the pressure difference would increase substantially choking o
28. move 2 screws holding float needie amp seat assembly in position Remove float needle amp seat assembly 13 Inspect needle for wear NOTE Needles are not available separately If needle is bad you must replace float needle amp seat assembly 10 98 4 36 Polaris Industries Inc FUEL SYSTEM CARBURETION Mikuni TM 38 Carburetor Service Carburetor Disassembly 1 Remove main jet starter jet pilot jet and idle Screw 2 Clean all passages in carburetor body with carburetor cleaner Dry all passages and jets with compressed air Replace gaskets and any parts which show wear or damage Carburetor Assembly 1 Install pilot jet main jet starter jet and idle screw 2 Install float needle amp seat assembly Polaris Industries Inc 4 37 10 98 FUEL SYSTEM CARBURETION Mikuni TM 38 Carburetor Service 3 10 11 12 13 Place carburetor in an inverted position Connect pressure tester to fuel inlet fitting Apply 5 psi pressure and observe for one minute The needle and seat should hold pressure indefinitely If the pressure drops carefully inspect the needle and the needle seat The needle can be replaced needle comes with float The seat cannot be replaced If the seat surface is damaged replace the carburetor Carefully inspect float bowl gasket and replace if necessary Install float bowl on carburetor Install float body In
29. n function is to supply fuel at low speed it does feed fuel continuously throughout the entire operating range Fuel for the pilot jet is drawn from the float bowl mixed with air regulated by the air screw and delivered to the engine through the pilot outlet The mixture is regulated to some degree by adjusting the air screw When the air screw is closed the fuel mixture is made richer as the amount of air is reduced When the air screw is opened the mixture is made more lean as the amount of air is increased Pilot Jet From idling to low speeds the fuel supply is metered by the pilot jet There are several air bleed openings in the sides of the pilot jet which reduce the fuel to mist The number stamped on the jet is an indication of the amount of fuel in cc s which passes through the jet during a one minute inter ER Indicator val under a given set of conditions Number Pilot Air Screw The pilot air screw controls the fuel mixture from idle to low speeds The tapered tip of the air screw projects into the air passage leading to the pilot jet air bleeds By turning the Screw in or out the cross sectional area of the air passage is varied in turn varying the pilot jet air supply and changing the mixture ratio Polaris Industries Inc 4 17 10 98 FUEL SYSTEM CARBURETION Slide Cutaway 1 8 3 8 Throttle Throttle valve cutaway effect is most noticeable at 1 4 throttle opening The amount of cutaway is
30. n the Specifications section chapter 1 select correct diameter Idle Gap drill gauge for the engine 9 Slightly lift throttle slides with throttle lever and insert idle gap drill gauge under throttle slide Allow throttle slides to return 10 Turn idle adjustment screw in as required until only a slight drag can be felt on the gauge 11 Repeat steps 8 through 10 for remaining cylinders 12 Verify proper throttle lever free play and adjust if necessary by loosening cable adjuster locknuts and turning adjusters out equally until throttle lever freeplay is correct Throttle Free Play Std 0 010 0 030 25 76mm EZ Throttle 0 050 0 060 1 25 1 50mm Polaris Industries Inc 4 33 Drill gauges with 8mm A SC been 8mm Tool Body nii Fo KEIHIN Carburetor Synchronization Tool Refer to Specification Section for Tool Part Number KEIHIN Insert tool under Slide push in until edge of tool body is even with air bleed orifice in carb body Forward Ill 2 KEIHIN zu un eg must extend to front edge of slide MIKUNI Center of slide under cutaway See chart for size vA il 4 Forward 10 98 FUEL SYSTEM CARBURETION Mikuni TM 38 Carburetor Service Wear eye protection when using compressed air or cleaning solvents Review all fuel system warnings found on page 4 1 before proceeding Carburetor Removal Disassembly and Inspe
31. ngine damage When selecting the proper main jet always use the lowest elevation and tem perature that is likely to be encountered 10 98 4 20 Polaris Industries Inc The function of a carburetor is to produce a com bustible air fuel mixture by breaking fuel into tiny particles in the form of vapor to mix the fuel with air in a proper ratio and to deliver the mixture to the engine A proper ratio means an ideal air fuel mixture which can burn without leaving an excess of fuel or air Whether the proper mixture ratio is maintained or not is the key to efficient engine op eration The engine of a vehicle is operated under a wide range of conditions from idling with the throttle valve remaining almost closed to full load or maximum output with the throttle valve fully opened In order to meet the requirements for the proper mixture ratio under these varying condi tions a low speed fuel system or pilot system and a main fuel system are provided in Mikuni VM type carburetors The Mikuni carburetor has varying operations de pending upon varying driving conditions It is constructed of a float system pilot system main system and starter system or initial starting de vice Float System The float system is designed to maintain a constant height of gasoline during operation When the fuel flowing from the fuel pump into the float chamber through the needle valve reaches the constant fuel level the floats rise When the buoyan
32. ora aer wo amr JE amr qoam 7 Sar we mem l meret 160 mxym E moams 770000707700 LL Pire o5 mers moms aser Doch 7 or mem Pire 08 more Pire os sry Pikret TO wma D Plot Ar Jet Plot AJ uz eme CSC CS The part numbers for main jets and pilot jets are the same as Mikuni VM round slide carburetors Polaris Industries Inc 4 3 10 98 FUEL SYSTEM CARBURETION 1999 Condensed Data Machine Engine Carburetor Std Std Model Model Model Mount Type Main Jet Pi amp No lot Jet Indy 340 EC34 2PM051 VM30SS 2 Zinc 150 Jet Needle Throt amp Valve E Clip Cutaway 340 Deluxe 340Touring Indy Sport EC44 3PM025 VM34SS 2 Zinc 185 35 6FJ6 P 8 2 0 AL Sport Touring 3 166 TranSport Indy XCF EC45PM011 VM34SS 2 Zinc 270 40 1 6DP1 P 8 3 0 3 480 Indy 440 XCR SN44 44 98A1 VM34SS 45 11 4 6DH7 P 4 2 0 1 3 286 Indy Trail Touring EC50PM044 VM34SS 2 Zinc 230 1 6DH7 P 8 3 0 3 166 Indy Trail RMK EC55PM021 VM34 2 Zinc 270 35 11 2 6DH7 Q 0 3 0 ACCS 3 480 Indy Super Sport EC55PMO11 VM34SS 2 Zinc 310 35 11 2 6DH7 Q 2 3 0 1 3 480 Indy 500 EC50PL172 VM38SS 2 AL 350 45 3 4 6F9 P 6
33. pre determined for a given engine to maintain a 14 1 air fuel ratio at part throttle A steep angle would indicate a fairly lean mixture because there is less resistance to air flow A flat angle would provide a much richer mixture because there is more resistance to air flow The venturi shape can be adjusted for each engine s breathing characteristics by using a different valve cutaway angle A number will be stamped into the bottom of the valve e g 2 5 indicating the size of the cutaway The higher the number the steeper the angle Leaner mixture Pilot Jet Needle Jet ps Main Jet Leaner Richer Throttle Valve The throttle valve controls the rate of engine air intake by moving up and down inside the main bore At small throttle openings air flow control is performed chiefly by the cutaway By controlling air flow the negative pressure over the needle valve is regulated in turn varying the fuel flow The throttle valves are numbered 1 0 1 5 2 0 etc according to the size of the cutaway The higher the cce number the leaner the gasoline air mixture Cutaway 10 98 4 18 Polaris Industries Inc The jet needle and needle jet have the most effect be tween 3 8 and 3 A throttle opening Some mixture adjust ment can be accomplished by changing the location of the E clip on the needle Moving the clip down raises the needle in the jet passage and richens the mixture Moving the clip up lowers the needle in the j
34. r flooding the engine With airbox venting the pressure difference remains the same creating a slightly leaner mixture to compensate for reduced air flow Vent Line Routing Opposite Carb to Handlebar Atmospheric Pressure Direction Th h S S Some Models Have Interconnecting Lines Between each Carb Tee Fittings Are Orientated Vertically Baffle Tube Air Box Some models have airbox venting 10 98 4 14 Polaris Industries Inc FUEL SYSTEM CARBURETION Fuel Delivery System Typical The fuel system contains many components which directly affect fuel mixture and driveability When performing diagnosis or carburetor maintenance the entire fuel delivery system should be inspected The illustration below shows parts of the system requiring periodic maintenance to ensure there is no fuel or air leaks present Fuel filters should be replaced at least once per season or more often if any contamination is suspected Fuel lines should be replaced every other season or more often if they become brittle or swollen Fittings should be inspected at that time for cracks or leaks Test run and check the fuel system for leaks any time parts are replaced Verify that all lines are routed correctly away from any moving parts Vent Lines Water Traps Cylinder Base Gasket Sa Le uel i Fitter Fuel Line Impulse Crank Weighted Pickup Line Bank Check Seal and Line Seal Valves Impulse Fitting
35. re jet needle and throttle valve 8 Inspect gasket under throttle cap Install throttle cable spring and collar Connect cable to slide valve 9 Install carburetor top cap until seated on carburetor body 10 98 4 32 Polaris Industries Inc FUEL SYSTEM CARBURETION Adjustments Throttle Synchronization Procedure Mikuni and Keihin 1 Remove air box noting position of throttle cable junction block Reposition throttle cable and junction block in same position when air box is reinstalled Throttle Cable Synchronization Throttle Gap 2 Referring to specification section in chapter 1 select correct diameter Throttle Gap synchronization drill gauge for your engine NOTE Keihin carburetors require a special tool with two drill gauges separated by an 8mm gap See illustrations at right 3 Back out idle screws about three turns 4 Slightly lift throttle slides with throttle lever and insert tool or drill gauge under throttle slide Allow throttle slides to return NOTE Be sure tool is positioned properly on Keihin carburetors see Ill 2 and Ill 3 Mikuni see Ill 4 5 Loosen lock nut and turn throttle cable adjuster on top of carburetor in clockwise or out counterclockwise as required until a slight drag can be felt on the gauge or tool 6 Securely tighten throttle cable synchronization lock nut 7 Repeatsteps 3 through 5 on remaining carburetor Idle Gap Synchronization 8 Referring to chart i
36. rs are calibrated correctly for their intended use It is not necessary to change needles for normal applications The following is intended to be used as information to better understand the operation of Keihin carburetors and does not suggest that a technician should be changing jet needles for any reason The only change for the needie that Polaris normally recommends is to the clip position Use illustrations below and the explanation to determine the affect and characteristics of different jet needles Keihin needles generally affect fuel delivery in three areas 1 The diameter D of the needle primarily controls fuel delivery from 1 8 to 1 4 throttle openings A needle with a smaller diameter at D would be richer than a needle with a larger diameter at D in the 1 8 to 1 4 throttle range 2 The length L1 of the needle mainly affects fuel delivery from 1 4 to 1 2 throttle openings A shorter needle will be richer and a longer needle will be leaner This produces same effect as raising or lowering the needle clip but to a larger degree 3 The taper A primordially controls fuel delivery from 1 2 to 3 4 throttle openings A steeper taper will deliver more fuel in this throttle position range EXAMPLE R 1370G Taper A R 1370G L1 and Clip Position R 1370G Diameter Q D R 1370G O 18 14 1 2 34 Full 2 515mm Throttle Opening R Aluminum Construction 13 Taper Angle of the needle depicted at point A
37. stall air adjusting screw Install throttle slide Install jet needle Install funnel Install carburetors on snowmobile Synchronize carbs as outlined on pages 4 39 4 40 Replace top caps 10 98 4 38 Polaris Industries Inc Throttle Synchronization Procedure Mikuni TM 38 Flatslide Carburetors Mikuni TM 38 carburetors are synchronized at wide open throttle without the engine running The middle carburetor on triples and the PTO side carburetor on twins have a non adjustable set screw on the throttle shaft This carbu retor is what the other carb s is synchronized to 1 Remove airbox 2 Remove top caps on all carburetors 3 Hold throttle wide open and view position of carburetor slide on set carburetor Middle carb on triples PTO carb on twins 4 With throttle held wide open turn the slide stop screw with screwdriver until slide is flush with top of carb opening Polaris Industries Inc 4 39 FUEL SYSTEM CARBURETION Adjustments 10 98 FUEL SYSTEM CARBURETION Adjustments Throttle Synchronization Procedure Mikuni TM 38 Flatslide Carburetors 5 On remaining carb s loosen phillips head screw inside the offset nut 6 When screw is loose hold throttle to wide open Turn offset nut until throttle slide is in same position as set carburetor 7 Tighten phillips head screw 8 Replace top caps 10 98 4 40 Polaris Industries Inc Choke Adjustments With
38. t repairable Polaris Industries Inc 4 25 FUEL SYSTEM CARBURETION Mikuni VM Carburetor Service Trap Nut m Ke Clamp Drain Plug T Gs 10 98 FUEL SYSTEM CARBURETION Mikuni VM Carburetor Service 10 Remove main jet and washer or spacer ring and push needle jet into the slide valve chamber to remove Clean air bleed hole in needle jet 11 Remove pilot jet Wear eye protection when using compressed air or cleaning solvents Review all fuel system warnings found on page 4 1 before proceeding 12 Remove pilot air screw and clean all passages in the carburetor body with carburetor cleaner Dry all passages and jets with compressed air Replace gaskets and any parts which show wear or damage 13 Reassemble carburetor adjusting float level before installing float bowl Refer to page 4 27 for float level adjustment and leak testing procedures 10 98 4 26 Polaris Industries Inc Float Level Adjustment 1 2 Remove float bowl With carburetor in an inverted position float arm A should be parallel with body B See illustration at right Arms must be parallel to each other To adjust float arm bend tang contacting inlet needle Never bend the float arm itself Leak Testing Needle and Seat 1 Be sure float level is adjusted properly 2 nvert carburetor 3 Install float chamber and connect pressure tester PN 2870975 to fuel inlet fitting Pressure Tester PN 2870
39. the dash mounted choke control toggle flipped to the full off position the choke plunger must be seated on the fuel passage way in the carburetor If the plunger is not seated on the passage way the engine will flood or run too rich causing plug fouling and very poor engine perfor mance If cable slack is too great there will be excessive toggle free play resulting in hard starting Also the half on position used for intermittent applications will not function If the choke lever assembly becomes damaged a lever kit is available This allows replacement of the lever assembly rather than the entire cable assembly Installation instruc tions are included with the kit Choke Lever Kits 2 Cylinder PN 2200188 3 Cylinder PN 2200189 Adjustment Procedure 1 Flip choke toggle to full off position 2 Loosen adjustment locknut A on carburetor s 3 Turn cable sleeve adjusting nut B clockwise on carburetor s until 1 4 6 cm or more choke toggle free play is evident 4 Turn cable sleeve adjusting nut counterclockwise on one carburetor until toggle has zero free play then rotate it clockwise until 1 8 1 4 3 6 cm toggle free play is evident 5 Tighten adjustment locknut A 6 Repeat steps 4 and 5 for remaining carburetor s Choke Lever Freeplay 1 8 1 4 3 6 cm 1 8 1 4 3 6 cm Freeplay Polaris Industries Inc 4 41 FUEL SYSTEM CARBURETION Adjustments Choke Choke Toggle Pos
40. to close so that fuel cannot return form the carburetor When the piston begins its downward stroke the pressure from the crankcase becomes positive causing the fuel pump dia phragm to move in the opposite direction and reversing the pressure in the fuel pump chamber This causes the inlet valve in the pump to close and the outlet valve to open filling the float bowl in the carburetor When the float level in the carburetor reaches its standard level the needle valve will close prevent ing more fuel from entering the carburetor even though the fuel pump continues to try to provide the carburetor with fuel Maintenance FUEL SYSTEM CARBURETION Fuel Pump Operation The impulse operated diaphragm fuel pump does not require any specific scheduled maintenance However the following procedures should be observed Operation The pump may be checked for operation by re moving the fuel supply line from the carburetor and placing it into a container With the engine idling at approximately 2000 RPM a steady flow of fuel should be visible Cleaning The pump and impulse line must be disas sembled and cleaned of foreign material in the event of piston or other internal engine part fail ures which produce fragments Inspection e Disconnect impulse line from pump Connect Mity Vac to impulse fitting or line and apply 4 6 PSI pressure Diaphragm should hold pres sure indefinitely The diaphragms and check

1999 Polaris Service Manual

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