GX390 carb VS rpms ???

dave269

Member
I have a slightly modified predator 212. What max rpm is a non-bored gx390 carb good for before it needs to be bored ?? Looking to turn in the 7500-8000 range.
 

subbietjw

Member
watch boring the 390 carbs when using them with the smaller 212/196/160... I have a pretty strong s/a-open and tried a bored 390 carb opened up just short of an inch and had problems with it.. it wasn't that it didn't run cause it made good power but it had a hard time starting!!! im sure it was jets but I had ended up detuning the untested motor to eliminate problems and haven't gotten it to full tune with the big 390 carb... but I got the jets close to running good at a .025 low and a .055 main with a 4x5 e-tube on pump gas.. as for rpm gains im not a 100% but ive herd of power gains in the 1+hp range
 
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