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Honda GX160 Tech Manual

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HONDA
TECH
MANUAL
GX160
HONDA ENGINE RULES
GENERAL RACING RULES SPECIFICALLY FOR
160 HONDA CLASS ONLY
Rusty Barnard, QMA Technical Director
First Issued: November 19, 1999
Updated November 13,2011
1

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  • Page 1 HONDA TECH MANUAL GX160 HONDA ENGINE RULES GENERAL RACING RULES SPECIFICALLY FOR 160 HONDA CLASS ONLY Rusty Barnard, QMA Technical Director First Issued: November 19, 1999 Updated November 13,2011...
  • Page 2 All shipping is to Express Mail at the shipper’s Expense 4 For the purposes of this rule only, if a handler has multiple cars competing in the Honda class (GX120 or GX160) 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.
  • Page 3 Inside seam of baffle must be straight edged. (NOTE: Some seams may not be parallel in baffle) You cannot cut off the threaded flange if it is to be used in Honda. It is OK to weld a washer or nut on the flange for a place to apply safety wire F.
  • Page 4 L. Exhaust oxygen sensor or temp. sensor attached to any part of Honda exhaust system is illegal. M. Valve seals are illegal. (Event DQ only NO suspension.) N. Cryogenics of any Honda part is illegal. O. Note: Taking parts out of service reference to “Wear Limits” in Engine Block Internal section.
  • Page 5 Material may not be added to throttle stop area of black plastic piece or carb body. 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.
  • Page 6 Air Jet Main jet size: maximum #82 - 0.033 no/go. Jet must be stock unaltered. As of 4-1-10 any jet pin goes in and sticks will be a DQ. Main air jet: 0.0587” maximum #53 (0.0595”) no go - at back of hole. Main jet access passage: 0.0942”...
  • Page 7 ENGINE COOLING SHROUDS All pieces of the stock engine-cooling shroud must be properly installed. 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 cooling fan.
  • Page 8 Remove valves: Retainer: 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”...
  • Page 9 Honda. They or their mounting position may not be altered in any manner. No heli-coiling of mounting holes. No bending of studs. Push rods will be stock Honda and will not be altered in any way. Push rod length will be 5.257-5.279”.
  • Page 10 HEAD Cylinder head will be in “as cast” and in factory machined condition and there must be no addition or subtraction of metal or any other substance to the inside or outside of the cylinder head. This include no type of machining or grinding to increase compression or airflow.
  • Page 11 Measure from surface of head to lowest machined area in the bowl of the port. This dimension will be: Intake: 1.062 - 1.170” maximum Exhaust: 1.103 - 1.122” maximum D. Thickness of head. This will be measured from valve cover surface to head gasket surface at the side at a position in line with upper intake &...
  • Page 12 NOTE: All measurements taken at top of bore or very bottom of bore. “Wear Limits/Parts Out Of Service” QMA reserves the right to confiscate 160 Honda engine parts deemed illegal or at QMA maximum wear limits. EXAMPLE: Cylinder Bore will be 2.681 Max.
  • Page 13 CAMSHAFT PROFILE LIMITS IN TAKE EXHAUST Degrees Degrees 0.050” 10.5 to 14 ATDC 0.050” 207 to 210.5 BTDC 0.100” 26.5 to 30 ATDC 0.100” 190 to 193.5 BTDC 0.150” 45 to 48.5 ATDC 0.150 170.5 to 174.5 BTDC 0.180 Split” 0.180 Split”...
  • Page 14 G. No metal may be added or removed from the flywheel. Flywheel weight will be: 2360grams minimum A stock Honda spark plug cap, (wire end and resistor), must be used. Any automotive type spark plug with ¾”reach maximum is allowed. Tapered seat plugs are not allowed. Race DQ only.
  • Page 15 Cover must be “as cast” and in factory machined condition and there must be no addition or subtraction of metal or any other substance to crankcase cover. Crankcase cover gasket must be stock Honda. Only one gasket may be installed with a maximum thickness of 0.025”...
  • Page 16 PISTON NOTES Piston will be stock Honda standard size and will not be altered in any way. A. Oversized pistons must not be used. B. All three piston rings must be used and installed properly.
  • Page 17 RINGS Must be stock Honda rings with stock size and configuration. No decreasing of ring tension by heating, machining or any other means. Ring thickness: Tier III Compression: 0.056” min. Compression 0.036” min. Scraper: 0.056” min. Scraper 0.036” min. Oil Ring: 3 piece oil ring = 0.095 min.
  • Page 18 D. Governor drive gear cannot be removed. E. Crankshaft drive gear should not be removed. This gear is installed by Honda to any accuracy of + ½ degree. If this gear is not installed to this degree of accuracy, engine may not be legal when camshaft is checked by the procedure under engine block.
  • Page 19 CAMSHAFT Camshaft must be stock Honda with no alteration of any kind. There will be no additions to or subtractions from any part of the camshaft. B. Compression release will remain intact and unaltered. C. Lobe center angle will not be altered by any means.
  • Page 20 Cylinder bore will be 2.682” maximum. Wear Limits/Parts Out Of Service” QMA reserves the right to confiscate 160 Honda engine . “ parts deemed illegal or at QMA maximum wear limits. EXAMPLE: Cylinder Bore will be 2.682 Max.
  • Page 21 PROCEDURE FOR CHECKING TIMING With degree wheel or indicator located at 0 degrees or TDC., mark both the flywheel and some fixed point (such as right hand side of aluminum block casting right above flywheel) with aligning marks. Turn the flywheel clockwise and stop at 26 degrees BTDC or 0.103”- 0.104” BTDC on your indicator. Make another mark on the block casting that aligns with your mark on the flywheel.
  • Page 22 DECIMAL EQUIVALENTS OF NUMBER SIZE DRILLS Size in Size in Size in Size in Decimals Decimals Decimals Decimals .2280 .1590 .0960 .0390 .2210 .1570 .0935 .0380 .2130 .1540 .0890 .0370 .2090 .1520 .0860 .0360 .2055 .1495 .0820 .0350 .2040 .1470 .0810 .0330 .2010...