Sparks said it will help and they also said JE is already making them some custom pistons that go all the way to 14:1 compression. They will also have other ratios cut. My cousin put the 13:1 piston in his wr and said the torque was way better throughout the powerband. I do not know how he does it but he just runs premium fuel. He has had it for awhile with zero problems. I still would up my octane quite a bit.

 

I doubt an ATV with it's added weight, would be able to get away with pump gas at 13.1 compression. At 14:1 you'd better start thinking about alcohol.

 

How much is that ti. yz exhaust? I don't happen to know. I'm sure its not cheap though

 

If I'm correct, the muffler alone is $530, and the header is $230. that comes to $760. Ouch!

 

I wonder if the high compression piston will hurt your topend performance? I know it will give you more bottom end.
But I woudn't want hurt my topend.

 

wow, thats a lot. Never mind. I'll just go with a pro circuit ti-4 or something. -Thats a good question, about if it hurts the topend at all. I was kind of curious about that myself. Also, would there be any negitive affects of putting the yz exhaust cam or doing the cam mod, to the yfz?

 

Ya there would be one negative affect, you would beat your buddies even worse.

 

When I talked to the guy at sparks racing he told me it would not affect top end but that it would actually improve it by running the 13:1 piston.