HONDA 160 UT1 TECH MANUAL
Contents
1. HONDA 160 UT1 TECH MANUAL USAC NATIONAL TECH DIRECTOR ERIC RANKINE FEBRUARY 15 2015 2015 UNITED STATES AUTO CLUB HONDA 160 011 TECH MANUAL Updated February 22 2015 FROM 2015 USAC NATIONAL 25 MIDGET RULE BOOK APPENDIX 731 Engine Protest Rules applies to Honda and Briggs classes only Protest shall be from within the same division of class only i e Jr Sr Lt amp 120 160 Animal or World Formula only Competitors in the same division and in the same race may make a protest on an engine No protesting in Rookie Class Handlers may not protest more than one car per event and may not protest same driver more than once per calendar year Honda Engines and World Formula Animal Engines may be protested for 400 00 cash only plus any applicable shipping charges if necessary No protested related inspection will be started prior to the funds being posted with the proper official This protest form and cash must be submitted to the Chief Steward or his her designee before the end of the race that the protested engine is participating in LE Checkered flag lap complete The protest can only be made during an A Main event The person protesting the motor must have their engine inspected for compliance first If the protester s engine is found illegal the protest is null and void and the protest fee will go to the club If the protester s engine is found legal the protest will continue The Chief Steward his2. maximum wear limits will be taken out of service If no measurements exceed USAC maximum wear limits the part of block will not be confiscated Handler has the right to have confiscated parts returned to them but will be rendered unusable Cylinder bore will not be bored oversize Cylinder bore will not be re sleeved Cylinder bore position will not be moved or tipped in any manner There will be no polishing sand blasting or glass beading to any interior surface Machined surface of block down to thrust face of cam boss 3 220 minimum 3 235 maximum 8 Machined surface of block down to bearing face 3 416 minimum 3 435 maximum 9 Oillevel sensor will be intact and unaltered Wires may be externally disconnected or cut off Nen pw Tech officials have the right to tech any or all cars in any class at their discretion Parts in question that need further review must be sealed and boxed up at the track in front of the handler The handler and tech director must also sign a slip indicating that they both acknowledge the part is in question The part must then be shipped to the USAC National office at 4910 West 16th Street Speedway IN 46224 USAC 25 GX 160 Tech Manual 33 Decimal Equivalents of Number Size Drills Size of Size of Size of Size of Drill in Dail in Drillin No Inches No Inches No Inches No Inches 1 20 a aso D pr D rm 2 0 2 asm D r e 20 E P D s 4 2090 agn D EN
3. any event that it s deemed necessary Any type of throttle linkage may be utilized Carburetor shall remain unaltered with the exception of the black plastic piece on the upper end of the throttle shaft This is the ONLY part of the carburetor that may be altered removal of material from the black plastic piece is allowed No additional material may be added to the carburetor Le bolt in black plastic piece or tubing on throttle stop Stock Honda fuel tank must be removed Recoil starter must be removed Pull cup may be cut down for washer Must use original cup Exhaust a Stock Honda muffler will be removed Mounting flange may be cut off of muffler and used as adapter flange Any transition from the D shape of the exhaust port to round must take place within the thickness 0 250 max of the flange This applies to all exhaust systems No steps or tapers allowed grind marks are allowed past 25 flange area No suspension for exhaust flange or pipe infraction just disqualification If an aftermarket flange is used maximum allowable flange thickness will be 0 250 If slip on type flange assembly is used pipe stub will be a maximum 0 880 outside diameter tubing with a maximum overall length of 1 500 Pipe stub must be inserted into exhaust pipe at least 0 750 and will have minimal exhaust leakage b AI USAC 25 midget mufflers to be used will be 4 to 8 hp Briggs amp Stratton part number 294599 or equivalent Muffler will be
4. be checked further USAC 25 160 Tech Manual 21 0 050 0180 0 200 CAMSHAFT PROFILE INFORMATION INTAKE DEGREES 105 14 265 30 45 48 mm 00 0227 PROCEDURE FOR CHECKING TIMING 135 141 180 185 0 050 0 150 0 200 MAX LIFT 0200 0 150 0 050 EXHAUST DEGREES 2065 2105 BTDC 1895 1935 BTDC 1705 1745 BTDC 144 148 00 BTDC 0 229 705 745 BTDC 445 485 BTDC 26 295 9 125 hm wmd USAC 25 GX 160 Tech Manual Magnet and or its position cannot be altered in any way Magnet retaining screw may not be altered in any way Screw may not be replaced with larger or smaller screw No heli coiling of mounting hole Ignition coil and or its position may not be altered in any way enge a mounting bolts must be stock and cannot be altered in any way to advance or retard timing Coil attaching bolts will be stock 6mm cap screw 1 1 16 long There can be no more than 3 8 of unthreaded portion of bolt that does not measure 0 230 diameter This restricts movernent of coil to a position that could make ignition timing illegal If a coil support mount becomes stripped it is permissible to heli coil However only one leg may be repaired if both legs are heli coiled the crankcase becomes illegal 6 All nylon blades on th
5. her designee will hold the protest money until the protested engine has been inspected for legality The protested engine shall be tagged marked and sealed as soon as it car comes across the scale if it has not been sealed prior The protested engine well as the engine of the protested party shall be immediately taken to impound and or presented to the Tech Director for inspection Engine must remain in impound and in the possession of tech officials throughout the entire process including shipping to USAC Headquarters designated tech inspection station and the transferring of funds USAC 25 160 Tech Manual 2 10 11 12 13 14 Both protester and protestee have the option to be present at the time of inspection Any protest that is withdrawn will be assessed 50 00 fee that will be paid to the host club If the protested engine is found to be illegal the motor must be completely torn down to check for additional illegalities The Tech Director must confiscate all illegal parts and related parts from the protested engine and shall immediately forward them to the USAC Headquarters If engine is found illegal protest money minus 50 plus any shipping cost will be returned to the person filing the protest Refusal of protest destroying or withholding of parts or any other lack of cooperation in this protest or inspection process shall be interpreted as an admission that the engine is illegal and shall su
6. internally unaltered except that the round cup shaped baffle may be welded to the perforated baffle without moving its original location No drilling holes in the baffles Inside seam of baffle must be straight edged NOTE Some seams may not be straight Threads will not be removed from muffler Itis ok to weld a washer or nut on the flange for a place to apply safety wire and or spring Exhaust pipe will be a maximum of 1 000 outside diameter with a length of 20 0 to 26 0 including a threaded pipe coupler welded to the end of the pipe in order to screw muffler in place so that muffler may be removed for USAC 25 GX 160 Tech Manual 5 inspection Pipe coupler will be a standard unaltered 34 NP threaded coupler Length will be 1 000 minimum to 2 250 maximum Exhaust pipe length will be measured by using small diameter hose inserted though pipe to measure overall length Flange and coupler will be included in the overall length when measuring pipe No coating of any type may be applied to the interior of any part of the exhaust system The intent of this rule is to have all of the exhaust pass through the muffler All measurements are to be taken with the component pieces in the same position as they were installed and on the car 9 Steel or Stainless are the only materials allowed for exhaust pipes Choke butterfly amp shaft must be removed Hole may be filled only with silicone or old shaft may be cut down No addition o
7. to the outside of air filter adapter Outerwear style or equivalent can be used over carburetor only with no adapter The approved air filter adapter may be run with or without an air filter Any air filter may be used with adapter as long as there no devices inside the air filter or adapter IE Springs not allowed Hose from valve cover must go into a catch can We are using outerwear to define a style not brand name The use of air filters during qualifying at asphalt and dirt events is illegal The Senior Tech Official reserves the right to allow filters at any event that it s deemed necessary Any type throttle linkage may be utilized Carburetor will be unaltered with the exception of the black plastic piece on upper end of throttle shaft this is the only part in the carburetor that can be altered Main jet is Non Tech Must be OEM Honda Jet Only modification allowed is drilling the main hole in the jet Rear mounting brackets for Honda fuel tank may be removed The starter cup that is behind the flywheel retaining nut can be cut away to leave only the flat washer back piece that retains cooling fan The keyed end of the ring gear shaft may be shortened drilled and tapped or machined for snap Heli coiling threads for shrouds all valve cover existing throttle mounting holes oil drain and fill holes one of the coil bolts and side cover bolts is allowed Dowel holes are not to be modified or relocate
8. 4 1 GX160 UTI PISTON 13101 Z4M 000 Max 02 685 Min 22 658 Max 0 140 _ Mox2 110 Min 0 134 Min 2 103 USAC 25 GX 160 Tech Manual 28 RINGS Must be stock Honda rings with stock size and configuration 1 No decreasing of ring tension by heating machining or any other means 2 Piston Ring Thickness a Compression 038 min b Scraper 038 min SSeS ISTE d Oil Ring 3 piece 095 min 1 1 piece 097 min 3 The letter N or T Tier Ill piston rings may not be legible after engine has been run WRIST PIN Stock Honda wrist pin and retainer a OD Minimum 0 708 Maximum 0 709 b Length Minimum 2 120 Maximum 2 128 ID 0556 ref d Weight 40 grams minimum USAC 25 GX 160 Tech Manual 29 CONNECTING ROD 1 Stock Honda rod with no alterations 2 Connecting rod big end size 1 176 minimum 1 184 maximum 3 Pin end bore is 0 710 ref 4 Length from bottom of pin bore to top of big end bore will be 2 3755 maximum 2 3580 minimum Rod weight with bolts 140 grams 6 No oil grooves on bearing surface of either end CRANKSHAFT JAPAN CRANKSHAFT THAILAND CRANKSHAFT USAC 25 GX 160 Tech Manual 30 1 Stock Honda crankshaft with no alterations 2 Noremoval or addition of any metal from or to the crankshaft is allowed 3 No balancing of the crank is allowed 4 Nooil grooving is allowed on the crank j
9. 60 UT1 INTAKE VALVE weie Min 0041 Min 20212 Max 20 949 Mn 094 L Max 2 488 1 Min 2 443 GX160 UTI EXHAUST VALVE USAC 25 GX 160 Tech Manual HEAD Cylinder head will be in as cast and in factory machined condition and there must be no addition or subtraction of metal except for the cylinder head gasket surface 2 No use of any substance to the inside or outside of the cylinder head This includes no type of machining or grinding to increase compression or airflow No milling or any alteration that could increase valve spring pressure 3 INTAKE AND EXHAUST PORTS 1 Ports will be in as and factory machined condition and there must be addition or subtraction of metal or any other substance to the inside or outside of the cylinder head 2 No alterations of any kind to be made to the intake or exhaust port a This includes any grinding polishing etching sand blasting or glass beading to interior surface 3 Seats must be a stock 45 degree angle Multiple angle valves are not permitted Valve seats must not be replaced 4 Intake and exhaust ports at valve Intake maximum 0 915 minimum 0 900 Exhaust maximum 0 863 minimum 0 858 Type to enter text USAC 25 GX 160 Tech Manual 19 This engine block must be in cast and factory machined condition There must be no addition or subtraction of metal or any other substance to t
10. 9 no go Tipof pilot screw 0 020 minimum s Floatbowl Vent 0 118 maximus 31 0 1200 no go Needle valve seat 0 0685 zaaximue 50 0 070 no go u The butterfly screw the butterfly and the throttle shaft must not be removed from the carburetor Any evidence of tampering will be a disqualification and suspension USAC 25 GX 160 Tech Manual 10 E Once you remove the Needle Valve you can then check the Needle Valve et dimension Remove the idle adjustment screw and then carefully pry up on the Pilot Air Jet to This is where the Pilot Air Jet is located There is not a spec for this hole The small hole in the bottom of the jet black plastic needs to be checked Also look to make sure that the o ring on the jet is there and in good condition USAC 25 GX 160 Tech Manual The Pilot Air Jet hole is just inside of this brass piece This needs to be checked with the proper no go gauge The hole at the end of the arrow is the Main Air Jet hole and will be checked using a pin type no go gauge Float Bowl Vent Pilot Screw Check tip and Pilot seat USAC 25 GX 160 Tech Manual 12 HONDA GX200 CARB FOR HEAVY HONDA a Must use Honda part number 16100 Z0V 921 b Mustuse Honda part number 16211 2 1 000 insulator for the Heavy 160 class This is the standard GX 160 Insulator No modifications allowed Carburetor Bore Intake e
11. D E 5 255 5 aes E p 65 1 D 200 25 D E 0030 7 E 27 D ams D 0920 D 1990 ES D aro 7 E 9 1960 m 1380 D no D 122 aes w 50 o m 177 aen 27 s 0670 n 7 D 1090 2 Am s 5 n 17 D Am s 0595 122 amo s 2 025 2 ES E 17 5s 0520 7 E amo ze E ss ven amo a 100 s E 18 ES E aos s ES mm 19 Aen E 05 E ono 2 E 2 vm E 0 USAC 25 GX 160 Tech Manual 34
12. Max 0 208 L GX 160 UT1 MAIN NOZZLE USAC 25 GX 160 Tech Manual 9 HONDA GX160 CARB FOR LT 160 amp BE65B BE65O UT2 T D cat BESAD Vi Mali T61SE ZHE WSO b Carburetor Bore Intake end Maximum diameter 0 951 ref lt Throttle end maximum diameter 0 710 d Carburetor venture bore 0 523 no go This measurement is best made with a no go gauge but may be made using a telescoping gauge as no go e Mainjetis nontech Must be an OEM Honda jet Brass or Silver Jets can be drilled to any size Only modification allowed is drilling the main hole in the jet 9 Main air jet 0 0587 maximum 53 0 059 no go at back of hole h Main jet access passage 0 0942 maximum 841 0 096 no go i Main nozzle bore 0 0732 maximum 47 0 0785 no go Main nozzle will be checked with a no go gauge 0 424 if gauge goes over main nozzle carb is illegal This is best measured using 01519 rod type gauge with a 0 424 flat area to be used as a go gauge Either the or UT2 main nozzle may be used Air vent holes on the side of the main nozzle must not be plugged Main nozzle must not be fastened into the carburetor body by anything other than the main jet It must not be epoxied or positioned by any other means m Pilotjet 00135 maximum 79 0 0145 no go o Pilot air jet 0 0478 55 0 052 no go Pilot screw no spec q Pilot seat diameter 0 0365 maximum 61 0 03
13. X160K1 HX2 HX26 engine and gearbox will be used in this class All parts will be stock Honda specifically made for the Honda GX160 OK1 HX2 U S GCAAK and Canada 8 GCABT Honda OEM 160 replacement block may be used Must be an OEM Honda replacement block No aftermarket blocks or components a 160 Honda engines must be updated to the new E2 Style piston and cylinder head b Failure to update and minimum 6 month suspension All stock Honda parts must be used and properly installed with the following exceptions Governor system may be partially or fully removed with the exception of the steel drive gear on the crankshaft This gear must remain intact If shaft is removed hole must be plugged Hole can be tapped for thread or epoxy No welding USAC 25 GX 160 Tech Manual 4 b Factory air cleaner must be removed Any air filter may be attached to the outside of air filter adapter Outerwear style or equivalent can be used over carburetor only with no adapter The approved air filter adapter may be run with or without an air filter Any air filter may be used with adapter as long as there are no devices inside the air filter or adapter I E Springs not allowed hose from valve cover must go into a catch can We are using outerwear to define a style not brand name The use of air filters during qualifying at asphalt and dirt events is illegal The Senior Tech Official reserves the right to allow filters at
14. bject the driver and handler to the conditions set forth in the Suspensions Program Any teched or protested engine block or part which are deemed to be over maximum wear limits in one or more spots but is under maximum wear limits in other spots is subject to confiscation but not DO able Note Reference to Confiscation due to Wear Limits in Engine Block Internal Rules of both Manuals If the engine is found legal 400 will be given to the person whose engine was protested 732 Engine Suspension Rules Handlers and drivers guilty of having an engine declared illegal at technical inspections shall be disciplined as follows First offense up to 30 days and or 4 race suspension for handler and driver from participating in the respective class at any USAC Sanctioned event Second offense within one year of first infraction up to One year suspension for handler and driver from participating in the respective class at any USAC Sanctioned event Third offense within two years of last infraction Suspended for life from USAC s 25 Midget division Suspension for life is open to review by USAC Suspension shall begin immediately Illegal Honda Animal and World Formula part s shall be sent within five Business days to the USAC office or designee for review The Tech director has 48 hours to determine if the part s are legal or illegal If the part s are determined to be legal it shall be returned to handler Handler shall be notif
15. d also one carburetor mounting bolt Honing and deglazing of the bore is allowed Lapping the valves is allowed Blocking Airflow No device may be used that will or appear that it may impede airflow into the engine cooling system This may require that the engine be run at a speed above idle by the tech personnel at the scale after the car has qualified raced USAC 25 GX 160 Tech Manual 7 160 INSULATOR 1 375 Mex 0575 Max Zeien mm ood Max 20 125 2 USAC 25 GX 160 Tech Manual AIR FILTER ADAPTER Remove Carburetor Air cleaner adapter ID 2 250 maximum Length 1 375 maximum Flange thickness 0 375 maximum Flange ID 1 000 minimum ID hole size straight walled flat bottomed and parallel with carburetor using existing air cleaner mount holes 1 Check for any alterations or worn parts that would allow additional air into engine holes slots perforations spacers loose bolts warped flanges etc 2 Gasket thickness 0 025 maximum 3 Insulator gasket thickness 0 025 maximum 4 Carburetor identification numbers 2 Light 160 BE6SB UT2 140 carb BESAD with Main Nozze 16166 b Heavy 160 BE64Y Check carburetor for alterations Upper choke shaft hole may be sealed with silicone type sealer Bottom hole may not be filled No addition of material of any type to the bore or venturi of the carburetor Paasio noso Pies They Ab
16. e cooling fan must be intact 7 No metal may be added or removed from the flywheel 8 Flywheel weight will be 2360 grams minimum 9 Flywheel diameter magnet area 6 285 10 A stock Honda spark plug cap wire end at resistor must be used 11 Any automotive type spark plug with reach maximum is allowed 12 No plug indexing washers allowed 13 If temperature sensor is used under spark plug factory washer may be removed USAC 25 GX 160 Tech Manual 23 GEAR BOX AND RING GEAR Gear box may not be altered in any way May be rotated to desired position Ring gear may not be altered in any way with the exception of keyed end of shaft that may be shortened drilled and tapped or machined for snap ring grove other machining drilling grinding etc to ring gear Keyway may be cut deeper Ring gear may not be altered in anyway including polishing or use of any compound or abrasive on gear shaft where bearings ride 4 Two gaskets maximum between gear box halves CRANKCASE COVER 1 Remove crankcase cover 2 Cover must be in as cast and factory machined condition and there must be addition or subtraction of metal or any other substance to crankcase cover 3 Crankcase cover gasket must be stock Honda Only one gasket may be installed with a maximum thickness of 0 025 4 Critical dimensions are thrust face of camshaft holder and position of crank bearing a Placea straight edge
17. ed a new piston for the UT1 GX 160 GX160 UT1 13101 24M 000 piston will be legal for USAC 25 midget competition beginning in 2012 The GX160 UTI piston 13101 24 000 will be stamped 24 00 on the top of the piston The side of the piston will be stamped Z4M USAC 25 GX 160 Tech Manual 2s vereent TOP VIEW GX160 UT1 PISTON 13101 24 000 SIDE VIEW GX160 UT1 PISTON 13101 24 000 9 current Tier Ill Honda GX160 Piston 13101 ZH8 020 and the Honda GX160 UT1 Piston 13101 24M 000 are both legal They both have the same measurements from the centerline of the piston pin bore to the top of the piston ring grooves included USAC 25 GX 160 Tech Manual 26 10 11 12 PISTON 13101 24 000 ZH8 PISTON 13101 2 8 020 Piston Weight a Z4M PISTON 13101 24 000 153 163 grams b ZHBPISTON 1301 2H8 020 158 168 grams Total Piston Weight Rings Pins Clips PISTON 13101 24 000 195 grams minimum b ZHBPISTON 13101 2H8 020 200 grams minimum Total Weight Rings Clips Rod amp Bolts Z4M 13101 24 000 USAC 25 160 Tech Manual 27 355 grams minimum b ZHBPISTON 13101 2H8 020 360 grams minimum 13 Piston Height 24 13101 24 000 49 0 mm minimum b ZH8PISTON 13101 ZH8 020 53 5 mm minimum 14 Min 22 668 x Max 22 665 Min 22 663 Max 02 678 Min 2267
18. ed in any way 2 Rocker arm studs will be stock Honda They or their mounting position may not be altered in any manner No heli coiling of mounting holes No bending of studs 3 Push rods will be stock Honda and will not be altered in any way Push rod length 5 279 maximum ENGINE BLOCK Wear Limits Parts Out of Service USAC reserves the right to confiscate 160 Honda engine parts deemed illegal or at USAC maximum wear limits EXAMPLE cylinder bore will be 2 682 max All measurements taken from top to the bottom of the bore parallel to crank 90 degrees from crank Any cylinder block that has one measurement over USAC maximum wear limits will be taken out of service If no measurements exceed USAC maximum wear limits the part of block will not be confiscated Handler has the right to have confiscated parts returned to them but will be rendered unusable 1 Check valves for dimensions and weight 2 seating surface must be factory ground to a single angle only 45 degrees There will be no other angles ground on any part of valve Valves must not be polished lightened or altered in any way 3 weight Intake 22 grams minimum Exhaust 22 grams minimum 4 Drawing of valve dimensions Intake valve followed by Exhaust valve USAC 25 GX 160 Tech Manual 17 Max 0 033 _ Min 0 022 Max 0 162 Max 0 0216 20212 0 988 1 Mn Max 2 514 Min 2500 GX1
19. eel 0 866 0 870 Heel to Peak 1 079 1 93 Heel to Peak 1 081 1 095 Length thrust flange to thrust flange minimum 3 142 maximum 7 Cam bearings are 0 547 0 551 and unaltered If the bearing falls under the minimum of 0 547 they will be taken out of service with no penalty TAPPETS 1 Tappets must be stock Honda with no alterations 2 diameter 0 909 minimum maximum spec 3 Stem diameter 0 312 minimum Base thickness 0 076 minimum 0 090 maximum Length 1 181 minimum 1 220 maximum Weight 16 grams minimum ENGINE BLOCK INTERNAL 1 The engine block must be an as cast and factory machined condition and there must be no addition or subtraction of metal or any other substance to the inside or outside of the block except for cylinder head gasket surface may be milled to achieve 0 00 piston pop up Cylinder bore will be 2 682 maximum NOTE All measurements taken from the top to the bottom of the bore preferred method of measurement is dial bore gauge dial calipers may be used Take out of Wear Limits Parts Out of Service USAC reserves the right to confiscate 160 Honda engine parts deemed illegal or at USAC maximum wear limits EXAMPLE Cylinder bore USAC 25 GX 160 Tech Manual 32 will be 2 682 all measurements taken from the top to the bottom of the parallel to crank 90 degrees from crank Any cylinder block that has one measurement over USAC
20. f material of any type to the bore or venturi of the carburetor Oil level switch may be disconnected but switch assembly must remain intact in crankcase 10 Gearbox may be rotated to any desired position 11 On Off ignition switch may be removed and hole covered any material welding 12 All pin measuring gauges are plus tolerance 13 Exhaust oxygen sensor or temperature sensor attached to any part of Honda exhaust system is illegal 14 Valve seals are illegal 15 Cryogenics of any Honda part is illegal 16 Taking parts out of service reference to Wear Limits in Engine block Internal section 17 DQ only No suspension for Exhaust Air Filter Adapter Spark Plug Gr more than 18 Shroud must be factory RED or BLACK 19 Honda gaskets for the intake carb side cover that are green on one side tan on the other are legal 20 Al seals must have the stock spring installed inthe seal and in its proper location TECH PROCEDURE Modifications or machining of any parts except the gasket surfaces between the cylinder head and block and main jet in order to bring them to a stated minimum or maximum specs blueprinting is not legal USAC 25 GX 160 Tech Manual 6 10 11 External visual check of engine for required components muffler shrouds and sheet metal and oil level sensor this can be partially observed from outside Factory air cleaner must be removed Any air filter may be attached
21. he inside or outside of the cylinder block crankcase cover crankshaft rod piston pin rings flywheel or coil with the following exceptions a Removal of rear gas tanks brackets is permitted b Removal of governor Governor system may be partially removed with the exception of the steel gear on the crankshaft This gear must remain intact Governor arm and shaft may be removed tied forward or altered to accommodate throttle linkage or return springs Addition of brackets fittings etc to accommodate throttle linkage tachometer temperature gauge is allowed Cylinder head gasket surface may be milled Check Bore 2 682 maximum NOTE All measurements taken from top to bottom of bore Preferred method of measurement is a dial bore gauge dial calipers may be used Take out of service with no or Suspension Check stroke 1 778 maximum 1 758 minimum Measure amount that piston is up down from block surface at T D C This will be measured at the edge of piston top and bottom and side to side When measuring top and bottom of piston take an average of the numbers measured i e top 7 003 bottom 003 the piston to deck would be 000 Measurement must NOT be taken in the center or relieved part of the piston The dimension will be 000 Max NO PISTON POP UP Carbon may be removed to check piston pop up USAC 25 GX 160 Tech Manual 20 10 11 12 Install degree wheel on flywheel Install pointer in order t
22. ied if part s are legal or illegal USAC 25 GX 160 Tech Manual 3 Allillegal or confiscated part s shall be sent to National Tech Director All legal parts shall be returned to handler If a Honda motor is found to have a valve oil seal during tech it shall be a disqualification only 8 Spark plugs and exhaust infractions are a race disqualification only 9 Failure to go to tech and or impound will result in a race day DQ Refusal of tech shall be interpreted as an admission that the engine is illegal and a suspension from the class shall be immediate with all awards and qualifications being revoked with a six month suspension driver and handler suspension at any USAC Sanctioned event 10 For the purpose of this rule only if a handler has multiple cars competing at one race event and more than one engine is found to be illegal at that event it will be considered to be one offense 11 All membership suspensions must be sent to the National Tech Director within 5 Business Days 12 illegal Rookie engine parts shall be confiscated Honda or Animal but the suspension shall not be levied against handlers or drivers for the first offense The second offense shall result in a 30 days Suspension from Rookie 13 cost to appeal suspension is 175 plus any associated fees The appeal must be made within 3 days of the ruling Unless it says you can do it you cannot do it GENERAL RULES Only stock Honda G
23. nd Maximum diameter 0 951 ref d Throttle End Maximum diameter 0 751 e Carburetor venture bore 0 576 no go This measurement is best made with no go gauge but may be made using a telescoping gauge as a no go Maiajetis nontech Must be an OEM Honda jet Brass or Silver Jets can be drilled to any size Only modification allowed is drilling the main hole in the jet Main air jet 0 0582 maximum 53 0 0595 no go at back of hole Main jet access passage 0 0942 maximum 41 0 096 go Main nozzle 0 0722 maximum 851 0 0870 no go Main nozzle will be checked with a no go gauge 0 449 maximum If the gauge goes over main nozzle carb is illegal This is best measured using 05572 rod type gauge with a 0 449 flat area used as a go gauge Air vent holes on the side of the main nozzle must not be plugged Main nozzle must be fastened into the carburetor body by anything other than the main jet It must not be epoxied or positioned by any other means Pilot jet 0 001 0 018 Pilot air jet go Pilot screw spec Pilot seat diameter 0 0345 maximum 61 0 039 go Tip of pilot screw 0 020 minimum Float bowl vent 0 118 maximum 31 0 120 no go Needle valve seat 0 0685 zaaximue 50 0 070 no go u The butterfly screws butterfly and the throttle shaft must not be removed from the carburetor Any evidence of tampering will be a disqualification a
24. nd suspension v Fuel inlet can be turned to clear blower cover n a USAC 25 GX 160 Tech Manual 13 G BEE cs voss Max 1 109 Thru Al amp PLCS Thu AN 1 8 200670 NOGO n 0 033 NO GO marozo PLC Thro Al Min 0 1960 GX 200 MAIN NOZZLE TOP END 1 Allpieces of the stock engine cooling shroud must be properly installed 2 There must be no addition or subtraction of any material from the shrouding except for the covering of the switch hole any material Starter cup may be altered to be used as washer retainer for the fooling fan 3 Remove engine cooling shrouds Remove valve cover 4 Zero dial indicator after exhaust bump 0 050 ref 5 Maximum valve lift will be checked from the top of valve spring retainer Valves may be adjusted to zero clearance or shims may be installed to create zero clearance This may dictate making special shims as it is difficult to insert feeler gauge blades so as not to interfere with indicator contracts on retainer Valve Lift Intake 0 245 maximum Exhaust 0 255 maximum USAC 25 GX 160 Tech Manual 14 CYLINDER HEAD HEAD GASKET VALVES SPRINGS 1 2 10 Remove cylinder head Thickness of head will be measured from valve cover surface to head gasket surface at the side at a position in line with upper intake and exhaust flange bolt No angle milling of surface 2 911 MINIMUM Head gasket thickness 0 040 minimum
25. o read degrees Locate accurate T D C This should be done with a positive stop type fixture and not established with indicator alone Cam will be checked with indicator reading off the top end of tappets which will provide zero clearance The inverted radius of the top of the tappet presents some problem to get accurate readings and to prevent binding of indicator stem Indicator holder and pistons are very critical in this operation Zero indicator on base circle of cam Be sure that compression release does not affect zeroing exhaust indicator Zero dial indicator after exhaust bump 0 050 ref Turning engine in normal rotation clockwise facing flywheel take reading at specified opening Readings must fall between specified degrees on the following chart Check max lift at intake and exhaust FLYWHEEL FAN AND IGNITION SYSTEM Caution should be used when removing flywheel Do not hit with hammer or other heavy objects Service manual show flywheel to be removed with commercially available 6 puller Another method is inertia type knocker that threads onto crankshaft end The transistorized magneto ignition is fixed at 25 degrees BTDC and may not be altered in anyway a Firing must not exceed 0 104 or 26 degrees BTDC Quick check turning flywheel clockwise if the leading edge of the depression of flywheel rim where the magnet is mounted is not still under the right hand coil leg at 115 BTDC it is probably illegal and should
26. ournal 5 Governor drive gear cannot be removed 6 Crankshaft drive gear should not be removed This gear is installed by Honda to any accuracy of degree If this gear is not installed to this degree of accuracy engine may not be legal when camshatt is checked by the procedure under engine block 7 Keyway location must not be altered in any manner B Measure thrust to crank gear side 3340 Min 9 Theonly cleaning method allowed is on the flywheel side of crankshaft for the purpose of removing calcium rust etc from the exposed end of the crankshaft This is permitted only from the seal grove out to the end of the thread of the crankshaft where the flywheel bolts on Only a wire wheel may be used in the cleaning process The use of Scotchbrite sandpaper or any other compounds or abrasives is illegal No material may be added or removed from crankshaft Thailand crankshafts have no heat treat marks 10 Crankshaft main journal at flywheel and gearbox ends may not be altered in any way CAMSHAFT USAC 25 GX 160 Tech Manual 31 1 Camshaft must be stock Honda with alteration of any kind 2 There will be no additions to or subtractions from any part of the camshaft 3 Compression release will remain intact and unaltered 4 Lobe center angle will not be altered by any means 5 Lobe profile will not be altered in anyway 6 Camshaft specifications INTAKE EXHAUST Heel to Heel 0 865 0 869 Heel to H
27. over crank bearing and cam boss thrust face These surfaces should be level b Maximum tolerance will be 0 005 There will be no alterations to crankcase cover This includes any alteration to crank bearing and camshaft holder position and height in an attempt to alter valve timing USAC 25 GX 160 Tech Manual 24 PISTON WRIST PIN AND PISTON RINGS Remove rod and piston triangle or boss on top of piston must point toward push rods Piston wrist pin and rings must be absolutely stock and not altered in any manner PISTON 1 Piston will be stock Honda standard size and will not be altered in anyway Oversized pistons must not be used The GX160 UT2 piston 18101 24 80D wil 3 Allthree piston rings must be used and installed properly Chrome compression ring installed with Thailand rings marked R on rail up No expander under ring b Middle ring Oil scraper ring installed with R on rail up expander under ring Bottom ring Three 3 piece oil rings are allowed Check oil ring expander for alterations that will alter ring tension cutting ends of expander etc 4 Piston may not be knurled grooved or coated 5 Total Piston weight with rings pin and clips 200 grams minimum Total piston weight with rings pin clips complete with rod and bolts 360 grams minimum 7 No decreasing of ring tension by heating machining or any other means 8 Honda has releas
28. thickness of inner rim Remove Valves Inspect retainers for alteration that would increase valve spring pressure Both intake and exhaust must have stock Honda retainers Exhaust valve only can have lash cap and corresponding retainer Thickness of retainer will be Intake 0 228 minimum Exhaust 0 241 minimum Flange thickness of retainer will be Intake 0 110 maximum Exhaust 0 070 maximum From flat of flange to machined surface Intake 0 148 minimum Exhaust 0 165 minimum All valve oil seals must be removed The use of valve seals is illegal and will result in applicable suspension per Honda suspension program USAC 25 GX 160 Tech Manual 15 VALVE SPRINGS VALVES INTAKE VALVE ASSEMBLY EXHAUST VALVE ASSEMBLY 1 springs will be stock Honda springs and will not be altered in anyway Use of Honda GX 120 or 140 valve spring is legal 2 160spring a Wire diameter 0 071 maximum b Outside Diameter of spring 0 71 maximum Number of total coils 5 3 d Spring pressure 11lbs maximum at 0 812 e Stacked length will be 0 394 maximum 3 140 spring a Wire diameter 0 079 maximum b Outside diameter of spring 0 808 maximum lt Total number of coils 7 d Spring Pressure 16 be maximum at 0 812 e Stacked length 0 524 maximum USAC 25 GX 160 Tech Manual 16 ROCKER ARMS PUSH RODS STUDS 1 Rocker arms will be stock Honda and will not be alter
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