Copyright 2003, Roadracing World Publishing, Inc.

This just in, from former racer Bruce Lind:

Performance evaluations for larger twin-cylinder
two-stroke racebikes in AMA competition.

A really good, late model TZ250 puts out about 85 bhp at the rear wheel on a Dynojet dyno.

Divide 85 bhp by 250cc. That yields 0.34 bhp per cc.

Assuming that this efficiency can be maintained while increasing the size and weight of the piston (which is highly unlikely) then the following engine sizes will yield the following BHP.

330cc X 0.34 = 112 BHP
350cc X 0.34 = 119 BHP
400cc X 0.34 = 136 BHP

Several very well know tuners believe that you can get 140-150 BHP out of a full 600cc four cylinder superbike.

I do not believe that you can actually get 136 BHP out of a 400cc twin cylinder two stroke engine, especially one that is developed by private individuals using a current TZ250 as the baseline, but limiting the displacement to 330cc will assure that the bikes disappear from the AMA scene.

Bruce Lind
AMA # 78 from 1978 – 2001
F-750, F-1, Sidecar, 250 GP
Retired after 37 seasons