> Thanx for the advice, sounds like I may wind up doing the
> exhaust afterall. I've got to paint the jug anyway. Just
> some followup questions if you dont mind...
> You say changing the porting on the intake would lessen the
> low end, would hit help the top end ??
A > As far as the intake goes... the engines I am most familiar with (from my age) all had reed valves... so my knowledge of non reed valve behavior is limited.
Also... If you are going to do the exhaust... DON"T do the intake at the same time!
You will not know which caused what.
> You said to keep the exhaust port coutour the same. I assume
> you mean the shape of the port. Aside from the obvious of
> matching the exhaust pipe,
A> First of all the shape is not round.. so it doesn't match the exhaust pipe anyway.
> is there another reason to keep the shape the same ??
A>Yes... the shape is meant to be friendly to the rings
Make the little V cuts like 1/8th" apart (maybe 14 of them total?)
That is the simple way to maintain the shape of the 3 'sides'.
> Does 1mm really make that much of a difference? Wow
With a 1 tooth gearing change I am pretty sure you will get 3 mph... and maybe even without the gearing change it will get that.
(however.. the speed comes from RPM.. the gearing is to help save your motor)
And I am telling you 1mm... because by the time you are done.. the 1mm tends to become a little more than 1mm... like maybe 1.5mm (1/16th)
You can go for 1/16th... and it will tend to become a little more.
Just trying to prevent you overdoing it... you can always go back in and do it again.. it is an easy process.
You only have to file the port surface about 3/4 of an inch back from the 'piston face'... not all the way out to the exhaust pipe connection.