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My Yamaha YL1 100cc Road Racer

This is how it looked when I built it in 1967. It wasn't quite as fast as a good 125 but handled better and weighed 150 lbs.

This is how it looks after I changed the rake and trail and used baby Ceriani forks. It now handles like my other frames. I also put a TA125 motor in it.

 

My new method of holding sections together for welding. Made from a piece of chain, threaded rod and a couple of bars.

The new pipes finished. I got the dimensions from Kevin Cameron. Also decided to start using air cleaners. I think it's faster than my MT125.

With the new pipes it makes 23 hp at 14K. I also did a little work on the transfers which Kevin recommended.
This bike uses Bridgestone 2.50-18 race tires you can get at a Honda dealer.

New TA125 heads. I had to make these after I destroyed one of the originals. This was before they were deburred.

New head beside an original after abrasive finishing.

The required oil pan even though I've never seen anything come out the bottom of a two stroke

The crankcase originally had pieces cast into it to stuff the lower end for higher crankcase pressure.

I cut it all away for better flow up into the transfer ports. I'll soon see if that works.

 
The next project will be to weld up the combustion chambers on some RD200 heads and machine them to fit. They have much larger fins and will cool better plus I had a crank failure and ruined one of the special heads I machined.
I also have to modify the chambers to lower the peak RPM. I think 14K is just too much for the rod bearings. When I rebuild the crank I will hone out the big ends of the rods a couple of thousands to give the bearings a little more clearance.