Scooterotica

So I got me a P150 motor on the bench. Was going to polish/match the ports any way so I thought I may want to increase the exhaust port width. (Stock ignition, crank and carb with new ring's and big bore exhaust)

In Scooterotica's old article (Dan's P200 vs Dave's T5) Dan's P200 motors simply had the exhaust port width increased by 3mm.

My question is, on a P150 motor will I want to stick with the 3mm width increase on the exhaust port or go with another (Smaller?) value?

Cheers

measure what it is now and then open it up to the 65% of bore rule as a starter if you can .

As Sean says.....65%

Got it!
Cheers.

So that's 57.8 x 65% = 37.57mm? And that's measured on the circumference, not straight across?

measure straight across the bore. so you get the 37mm edge to edge not around the bore ( use a calliper gague). if you can keep the top 50% of the port flat and then radius down to the outer edge and keep the outer edge of the port rounded (to help stop the rings snagging), you may find it better