High Comp Piston YFZ

[joedrives2fast]

I recently put a 13.5:1 piston in my 04. It runs great I took my time and did it right. My only question is do I need to re-tune my carb.

Now maybe I'm over thinking but...

if I had my jet's right before the piston swap since I didn't change the displacement of the engine the fuel ratio should be the same. Hence I wouldn't need to change the jetting. BUT...

With more compression I could add more fuel to the mix resulting in a stronger combustion which equals more power....

I haven't changed the jet yet to try but I'm worried about running too lean and burning up my long awaited piston. So I havent been out beating it too hard yet.

[Jeremy]

A lot of the time no fuel adjustment is needed because the higher compression piston will actually have a stronger pull on the intake charge which gets it the extra fuel it needs.

To put your mind at ease just take it to one of the local dyno shops and have them dial it in for you.

[CADWELL]

I would have to agree with Jeremy. Unless any unusaul jetting symptoms appeared after adding the HC piston I would leave it alone.

More importantly I would make sure to use the right octane fuel to avoid detonation. On 13.5:1 I would straight 110. Remember that on a '06 and up stock compression is 11.4:1 so any piston for a YFZ will be about .5 lower. So a 13.5:1 piston will actually be ~13:1.

The YFZ pistons are based off the '04-'05 compression which is 11.9:1.

[joedrives2fast]

Thanks for the reply's guys. I didn't think there was a problem but I just got my mind spinning on it.