acotrel
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- Joined
- Jun 2012
- Messages
- 15,036
I thought I might run something which I have done, past this forum - to see if you think it was silly. - I built a methanol fuelled T250 Suzuki road racer, won a race with it, then immediately sold it to a kid in the Hartwell Motorcycle Club called Ian Whitehead. When I encountered the bike again in about 2003, it had won 28 races and 4 historic championships. Whenever the barrels were replaced, they copied the porting. When I was porting the barrels, I had heard about people cutting 5 mm out of the tops of the transfer ports. My thought was that Suzuki would make their road bike motor ports fairly close to their TR250 works racer, which in the mid-1960s was faster than the Yamaha 250 equivalent,
I started thinking about revs and resonance and timings. The best Triumph 500cc four-stroke race cam was the E3134, and the usable rev range of the motor is similar to that of the T250 Suzuki. So I developed the equation which converted degrees of crank rotation to distance from top dead centre for the Suzuki T250, and used the Triumph E3134 timings. 1.5 mm out of the top of the Suzuki transfer ports gives an opening timing of about 60 degrees before top dead centre, and 3mm out of the top of the exhaust gives an opening timing of about 80 degrees before bottom dead centre. The expansion chambers were Yamaha TD3.
I used a computer to calculate and print out a list of conversions of crank rotations in degrees related to piston distance from top dead centre in millimetres.
I started thinking about revs and resonance and timings. The best Triumph 500cc four-stroke race cam was the E3134, and the usable rev range of the motor is similar to that of the T250 Suzuki. So I developed the equation which converted degrees of crank rotation to distance from top dead centre for the Suzuki T250, and used the Triumph E3134 timings. 1.5 mm out of the top of the Suzuki transfer ports gives an opening timing of about 60 degrees before top dead centre, and 3mm out of the top of the exhaust gives an opening timing of about 80 degrees before bottom dead centre. The expansion chambers were Yamaha TD3.
I used a computer to calculate and print out a list of conversions of crank rotations in degrees related to piston distance from top dead centre in millimetres.