ORIGINAL: Ralphbf
A string trimmer would gain from added compression.
That's what I did. From calculated 8:1 I got 10:1
ORIGINAL: Ralphbf
Because the chain saw comes in a higher state of tune, more compression, larger ports and more agressive timing
you are actually detuning it, lowering the compression, to deal with preignition.
You should also be able to adjust the timing, change grades of fuel or lessen the load to deal with preignition.
Taking out the Nitro from the fuel mix solved the problem. Metanol-Gasoline-Oil mix is not pinging
. Increased compression (without changing anything) rised the top rpm from 7020 to 7160 (APC 17x6). Original ZAMA carb (about 8mm venturi) and gutted mustock muffler.
RysiuM