Chainsaw Repair

eric gorr writes how this stuff can be useful. (will post the link up when i find it again).

i am not the best explainer as y'all can already see, because i look at these thing with graphs and such.

so, by varying the length and area one could raise or lower the intake tuning just about anywhere in the rpm range and nudge power band hit around a bit.

by using a spacer, lowering the tune for more of a torque hit is possible.

1/2 inch spacer, between the carb and intake port spigot, lowers the rpm hit by 700 rpm.
1" spacer....................................................................lowers the hit by 1200 rpm.

going the other way, shaving a 1/2" off, yields about an 800 rpm raise in the intake tune.

imo, a tach or the way chrispa suggests would be necessary to get rpm readings to realize the intake tuning benefit. or, if the tach won't read on the new fangled motors.  how anyone ports without a tach is beyond this discussion. 

as far as the case volume thing goes, for my motor, they picked a very good volume already.  don't know about others. porting raises the rpm, with not much to worry about as far as intake tuning, at least from the one example i am basing this on.

for the race crowd:  looked at what only decreasing the case volume, would do on my little motor.
for every in3 reduced case volume, about +700 rpm intake tuning went up.  not that much.
however, when port area was increased by about 30%, with 2 in3 less volume, rpm tune went up about 4000 rpm, max rpm up to 17.5k

eric gorr and frits overmars/jan thiel do have some interesting reads.