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My Yamaha YA6 125cc Road Racer

This is my stock, un-restored YA6. Runs great but doesn't look much like something you would want to road race. 

 

This is how my YA6 trail bike looked after I decided to turn it into a roadracer. I bought it for $73 in the early 70's and it already had a GYT kit. I made the pipe and tank and it vibrated so bad I couldn't keep my feet on the pegs. The front brake is from a CB92 Honda. It's magnesium and useless.

 

The next year I made the new frame and for some reason it hardly vibrates at all. Maybe it had something to do with that sheet metal frame.

 
I made a dry clutch for it and a couple of pipes. My next bright idea was another carb from an RD200 feeding into the crankcase through a reed valve. I did that because I was limited to a 26mm carb on the rotary valve. It seemed to work so I enlarged it to a 26mm from a CT1. I also made a couple of transmission gears and now it only drops 1000 rpm from 3rd to 4th. Next I'll try to make some straight cut gears for the primary drive.

I welded the new mount in but had to use some JB Weld where I wasn't a good enough welder to get into the small spaces. I had to enlarge the port to fit the larger CT1 reed valve. I'm going to try to machine the flywheels so the reed valve has more room to feed into the crankcase.

This is what it looked like with the RD200 carb. I made a progressive cable setup so one carb opens first but it probably isn't really needed because you're at full throttle most the time.