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Clone Stock Appearing Rules

9th Oct 2014


Clone Stock Appearing Outlaw Rules

The following rules are something I wrote up last fall for tracks to use as a template for a stock appearing class for the clone engine. Thease rules are intended to allow the average guy to build a powerful yet still durable engine in his own garage while keeping a lid on the potential costs of high priced modifications. Stock appearing has always been my favorite class because it is not so riddled with rules and it makes enough power to keep things exciting.


From 6 feet away, the engine, unless otherwise noted, must appear like a BSP, or Harbor Freight 6.5 HP engine. Parts may be interchanged between engine types.

Internally, you can change whatever you want as long as it meets the restrictions below. The restrictions are only for safety, cost control and containing performance to provide reasonable durability expectations.

Fuel tank must be relocated and a fuel pump, pulsed from anywhere on valve cover or crankcase, may be used.

Any throttle mechanism allowed that works with the stock throttle shaft’s bell crank. Remaining stock throttle mechanism parts may be removed.

Fuel is methanol only. (or gas only***track option***) A pump-a-round or similar community fuel pool is encouraged.

A plate may be bolted to the top of the engine to mount fuel pumps and/or throttle mechanisms.

Choke may be removed from carb. If removed, choke shaft hole must be plugged.

Pull starter may be replaced with a flywheel cover and any electric starter nut may be employed.

Aftermarket air filter adapter with a max length of 1.375” is allowed. Air filter may be up to 8” long.

Any header is allowed. No muffler unless required by track. If required use RLV-4106.

Unaltered SFI certified billet flywheel mandatory with stock ignition module only.

No welding or addition of material of any kind (e.g. epoxy) to the head, side cover, block or carb.

*Stage 2 Tech: In addition to the above, remove valve cover and check:

Rockers, pushrods, valves and valve spring retainers must appear stock. Valves and retainers may be used in any combination on either side. (e.g. exhaust valve, retainer and lash cap on intake side)

Max lift taken off the top of the valve spring retainer is .280”

*Stage 3 Tech: In addition to the above, remove head and check:

Piston must be flat top or dished and may not pop up above deck.

Max cylinder bore is .035” over stock bore. Stock bore is 2.685"

Valve head diameters must be between .940” and .990” and must appear stock

Max Stroke is 2.133” taken from top of piston