Yamaha DT 50 pipe and jet
I'm getting good results using a DT50 main jet. I turned it down slightly and ran a tap over it to make it fit in the stock carb.
I also used a DT50 chamber that I cut and modified. I tried to keep the pipe the same length as the original yamaha length.
You can check it out over on the rat rod section. Rat gone woody.
It pulls like a train. It 4 strokes right at the top end if I am ringing it's neck, but I don't ride like that normally. I may take some time and tune it out in the future.