Ported 50cc = stock 60cc?

[tree monkey]

Can`t agree with you there! A WELL modified saw is like the factory should have made it, but didn`t of different reasons. The porting is more ballansed, carb venturi is the correct sice, muffler is more open to prevent exhaust blowback, sqish clearense is correct, and so on. Bottom line, the modified saw will be more reliable. :msp_wink:

can you explain exhaust blowback?
thanks

 

[GBD]

can you explain exhaust blowback?
thanks

If cylinder pressure is higher than crankcase pressure when transfers open, exhaust will start blowing down the transfers. This shortens the effective transfer period and hurts the filling of the cylinder. It can also lead to carbon buildup. Mainly two things contributes to this, which are
too small blowdown timearea and too small muffler outlet.

 

[tree monkey]

i call that back stuffing
thank for splainen

 

[HEAVY FUEL]

i call that back stuffing
thank for splainen

I've seen pictures of back stuffing over on the WTF thread! Not pretty!!