Discussion in 'Performance Mods' started by philcred, Jul 3, 2007.

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  1. philcred

    philcred Guest

    does anyone have any specs for porting an 70cc /80 engine.

  2. Egor

    Egor Guest

    How far do you want to go? I start with the exhaust, I raise it to 1.1" from the top. I keep the port shape rounded at the top the help the rings transfer. I lower the intake port to lengthen the intake timing, you can also cut the piston skirt to get it out of the way at TDC. I cut the webbing at the bottom of the transfer ports out of the way, down at the crank end, a lot of the new engines don't cover the ports at all, so looking from the side of the cylinder upside down the web is shorter. So far I have left the intake ports as they were. The engine will out pull the two whzzers I go riding with, but, they have a higher top speed. I will not spin my engine that high. Have fun, Dave