RATPRO REGULATIONS

Honda GX 160 Technical Regulations

GENERAL

The scrutineer will pay special attention to ensure that the fi nish of all components match those of the standard unit and reserves the right to compare any part from competitors’ engines directly with a standard part as supplied by Honda (UK). Unless competitors have gone out of their way to source alternative parts, their engines should automatically comply with this rule. Furthermore, competitors should note that the term “standard” refers not only to the components used but also to the number used and the manner in which the engines

are assembled. Please remember that save for the changes specifi cally mentioned in these

regulations the engines must be completely standard unmodifi ed, and that all components will

remain in place unless this document specifi cally states that they are allowed to be removed.

No specifi c coating procedures are allowed on any internal or external surface of the engine.

Carbon or gasket residue removal must be achieved by use of chemical agents only, to

preserve original fi nishes. The fasteners on the engines may be drilled for the purposes of

lock wiring. Replacement of external fasteners with non-Honda fasteners is only permitted

when the replacement fastener improves safety or when the standard Honda fastener is

not readily available. A thread recovery procedure is acceptable providing that the system and replacement fi xing used are of no different size or pitch to the original and therefore offer no mechanical advantage over the original fi xing.

DEFINITIONS

The standard, unmodifi ed component This means that the component has not had its substance altered in any way. It has had no material removed from it or added to it. It will be of the same, original material. Where appropriate, it should have the manufacturer’s original manufacturing process or machining marks on it.

Engine types

The original QHQ4 engine, to engine number 7664037, shall in this document be called the K engine. The QHQ4 engine from engine number 7664037 onwards shall in this document be called the E engine. The QHQ4 engine with suffi x T, from engine number 1000000 onwards shall in this document be called the T engine.

Legality limit

In general terms, and where not clarifi ed or qualifi ed elsewhere in this document, the legal limit for eligibility purposes shall be deemed to be the service limit as specifi ed by Honda in the most up-to-date Honda Service manual for the particular engine. (http://www.honda-engines-eu.com/en/welcome.html)

COMPONENT BY COMPONENT

The fuel tank

It is strongly urged that the engine’s integral fuel tank be removed. If this is done then the engine must be fitted with a suitable cover. A standard floor mounted fuel tank should then be used, unmodified and this tank and its mounting must be in accordance with chassis manufacturer’s instructions or homologation. The capacity of this tank must not exceed 7.5 litres. Ballast may be added to the tank in order to maintain the maximum capacity. In this instance the kart may be fitted with a pulsed fuel pump(s), which will take a vacuum feed from either the governor rod hole or one drilled in the inlet manifold, tapped to accept a vacuum fitting. Fuel pipes must take a direct route to the carburettor and be safely secured. An extra loop of fuel pipe may be used as a return feed to the tank. One in-line fuel filter of nominal capacity per engine may be fitted.

Exhaust

The standard exhaust must be used but a unit modified and sealed by Prokart Engineering may also be used. In this case, the unit will bear a seal applied by Prokart Engineering and it is the competitor’s responsibility to ensure this seal is in place at all times. At any time the modified unit on the engine can be exchanged with one held by the scrutineer, who will then send the competitor’s exhaust back to Prokart Engineering for inspection. If this unit is found to have been tampered with in any way, then the competitor will be penalised retrospectively. No other repair or modification is permissible. Prokart Engineering can be contacted at 0796 735 8862 or www.prokart.co.uk

Carburettor

There is no restriction to the use of standard, unmodified A, B or C type carburettors with any of the engine types. However all carburettors are subject to normal dimensional criteria. Overall length (manifold face to airbox face) is 54mm and bore go / no go gauge is 13.2mm / 13.3mm.

Permitted main jets

size 68 (PN 99101-ZF5-0680) size 70 (PN 99101-ZF5-0700)

size 72 (PN 99101 -ZF5-0720) size 75 (PN 99101 -ZF5-0750)

Emulsion tube can be either part number 16166-ZH8-W50 or part number 16166-ZH-810 (see drawing 1 in Appendix). The throttle-actuating arm can be modified to accept an actuating rod onto the throttle butterfly, a method of mounting a throttle actuating cable and a method of mounting a throttle return spring only.

Carburettor air box

Must be standard unmodified.

Air filter

Substitution or complete removal of the renewable paper/foam air filter is allowed, although the plastic outer cover must remain as standard unmodified and in place.

Spark plugs

Spark plugs fitted to the engines must be from the recommended list provided by Honda - please see below. No other spark plugs may be used. The plugs used must not be modified in any way whatsoever and must have a reach identical to that of the plugs listed. Resistor plugs will be used. The standard Honda resistor spark plug cap - as supplied with the engine - must be used.

Permitted spark plugs

NGK BPR6ES BP6ES BP5ES BPR5ES

Nippondenso W20EP-U W20EPR-U W16EP-U W16EPR-U

Bodywork / ducting

All of the bodywork and ducting must be standard unmodified except for the drilling of a small hole to accept one end of a throttle return spring. The pull-cord mechanism must be standard unmodified, although the pull-cord starter may be rotated on its standard mounting holes. All or any of the bodywork / ducting can be painted or chromed.

Rocker cover

Rocker cover must be standard unmodified, although it may be painted or chromed. Its valve must be present and in working order. The breather pipe must be in position and intact, of suitable length that it is securely fixed in both the rocker cover and the outlet of the airbox, and have no perforations or leakage points.

Valve Gear

The valve rocker studs must be standard unmodified. The inlet valve collet (PN 14771-ZE1-000) may be replaced with an exhaust valve collet (PN 14773-ZE1-000) and an exhaust valve rotator (PN 14781-ZE1-000). If this modification is performed to the inlet valve, it is permissible to fit one 8mm washer between the cylinder head and the base of the valve rocker post to raise the post and ensure that the adjuster locknut sits on a full thread. The valve spring used must offer no mechanical advantage over a standard GX140 valve spring (PN14751-ZE1-000) i.e. a force of 5 kg will compress the spring to less than 25mm overall length. Valve rockers, cam followers and pushrods must be standard unmodified.

Valves

Valves will be standard unmodified. Valve-seat grinding and cutting is allowed, to standard profiles (including seat width) as specified in the latest Honda manual for the engine type.

Cylinder head

Will be standard unmodified and measure a minimum of 73.98mm from the rocker cover gasket face to the cylinder head gasket face. Ports must be standard unmodified. The standard de-burring marks and sharp edges should always be present.

Head gasket

Must be standard unmodified and will at all times have a minimum thickness at all points of 1mm.

Piston

The dished piston must only be used with the cylinder head from the K type engine. The flat-top pistons are interchangeable between the E and T type engines only and must not be used in the K type engine or with the K type head. Piston rings will be standard unmodified. Only standard size rings, marked T or N can be used. Either the single or three-piece oil control ring can be used on all engine types. The rings must always be free in their grooves to function as designed.

Connecting Rod

The standard unmodified unit is interchangeable between all three engine types.

Crankshaft

The governor gear can be removed. The position of the cam gear wheel is free. The standard key must be used. The crankshafts are different between all three engine types but are interchangeable between all three engine types.

Flywheel

The flywheel will be standard unmodified and is interchangeable between all three engine types. It must have a minimum weight of 2.35kgs. The standard unmodified fan shall be used, with all fins in place.

Ignition coil

The ignition coil (including ignition lead and plug cap) will be the standard unmodified unit and is interchangeable between all three engine types. The coil mounting bolts must be standard unmodified and use the original mounting positions.

Camshaft

The standard unmodified camshaft must be used, which is interchangeable between all three engine types. The service limits are 13.916mm for the journals and 26.65mm for the exhaust and 27.60mm for the inlet lobes.

Crankcase

The crankcase can only be modified by the removal of the governor mechanism and in all other respects must be standard unmodified. If completely removed, the hole in the crankcase must be sealed to prevent oil leakage. The crankcase bearings will be standard unmodified. The bore must be standard only, service limit 68.165mm at all points of the bore. No sleeving or surface material change to the cylinder bore is allowed but honing is permitted. The cylinder mating face should always have the manufacturer’s original finishing marks visible. A deck height of between 44.95mm and 45.06mm should be read between the cylinder mating face and the centre of the piston crown with the piston at bottom dead centre. When measuring a K type engine, 1.4mm should be subtracted from the obtained reading, to accommodate the dish in the piston. (See drawing 2 in Appendix).

Gaskets

All gaskets must be standard unmodified. Where there is any doubt about the eligibility or suitability of a particular gasket it should be compared with a new item from the manufacturer.

Clutch

A dry, air-cooled centrifugal clutch of Noram, Horstman, Magnum, Maxtorque 1600 or 4000 series type must be used to transmit the drive. The clutch should be in standard form (as supplied), be incapable of adjustment in position and have a maximum engagement speed of no more than 2,500 rpm engine speed.

PN 16166-ZH8-W50

Major bore 1.9mm max

0.68mm max

0.76mm max

0.68mm max 28.10mm

min

PN 16166-ZH8-810

Major bore1.8mm max

2.01mm max

0.66mm max

0.43mm max 28.18mm

min