What fuel?

[Legacy37]

So my 96 xp is about ready to run....carb rebuild, new fuel lines, etc. it seems to have an aftermarket head on it and has 165psi compression both cylinders. What fuel should it run? I know with 4 stroke engines the high compression engines need more octane

 

[mikidymac]

If it really has an aftermarket head and 165 psi then 91 octane.

 

[Legacy37]

I don’t think this is a factory head.....compression is definitely 165 with an accurate gauge ....not harbor freight

 

[mikidymac]

Definitely an aftermarket head. At 165 you should be fine with 91 octane.

The very generic rule of thumb is anything over 180 psi needs race gas.