So .... I’ve competed in a couple of historic events this summer .... literally the best fun I’ve had in ages.
My plan was to use them as a scoping mission and then build a compete experience bike over the winter .....
So light and quick off the start are the key requirements....
Engine wise I have some 250s and a 360 ...
Some GYT kit - air box/carb/muffler/head 250
Webco head 250
X1 aluminium Rim rear wheel
.........
I’d like to build a period racer that’s reliable ......

I’d like to hear from you guys who have built bikes and can share with me the knowledge and help me build a competitive bike please......
Cheers
T1

I’ve built a couple of race bikes, vintage motocross, over the years, but I haven’t built a Yamaha. Sadly the vintage, ‘71 through ‘74, classes are getting smaller in our two local series and the last vintage bike I built is not “legal” for AHRMA competition. Best advice I can offer is to work with a tuner who can help match cylinder porting, combustion chamber (shape & size), carburetion and expansion chamber.

Here's a picture of an RT3 I built this year for competition. It was a lot of fun and I raced it Sept 26th at a charity Vintage race in Ohio. It was allot of fun.