Hello Forum members. I'v'e been a long time trying to access this site. always having trouble logging in. Anyway i am a Yamaha fanatic from Burleigh heads on the gold coast. I recently rebuilt the top end on my 1967 yas1. I have a book written by yamaha in the 70's outlining mods that can be done to achieve more hp to piston ported two strokes.
The cylinders were raised 1mm using a spacer made from .8mm aluminium and an additional gasket, this raises all ports 1mm. The top of the cylinders had 1mm removed to keep the piston the same height at tdc. I also had 1mm removed from the heads raise compression also to bring squish clearance to .8mm. The pistons had 3.5mm removed from the bottom of the piston skirts to allow more fuel intake. All up these simple modifications along with new seals and rings has really transformed this little 125. It will now pull 60+mph in 4th gear on a road iv'e tested before. before mods it would struggle to reach 50-55. I now plan on building expansion chambers inline with specs obtained for these mods.
Does anyone on the forum own a yas1? has anyone built chambers for a yas1 or as3, rd125. Anyway i just wanted to get my first post on the forum and discuss the mods i have done. gman
