I have a few questions about the aftermarket pistons. I have a Stage 2 hotcam that has been sitting on my shelf for about 6 months and plan to get an aftermarket piston to put in at the same time. I've seen the JE that is the 102mm that ebay is selling and says it is a 686. The only thing is, is that it says it is available as 11:1 OR 12:1. I thought that the compression also says something about the displacement? How is it that the 11:1 and 12:1 is both a 686? It also says that with the 11:1 that you can run pump gas, but with the stage 2 cam, I can't run the pump gas anyway, so would it be better in my case to get the 12:1? I know I'll have to change the rod. Any recc. on what else should be changed? Also, I have seen that there are stock bore pistons that will make a bike run better, how could this be if the cylinder is not bored? Another thing, is there a sleeve that is changed or is the cylinder itself bored? I know there are some pretty stupid questions in here, but I don't know the answers so any help is appreciated[img]i/expressions/face-icon-small-confused.gif[/img]. Links would be good too if someone knows of a good one.

 

the compression doesnt have anything to do with the displacement of the motor. I know they say to run 100 or highier with the stage two but i would geuss that if you ran a 11:1 piston you could run super unleaded and be ok. I would get some other opions on the race gas for i"m just geussing.

 

Thanks ccgrady, did you do the engine work on your quad or did you get it done? If you did it was it hard, and what should I watch for? Any one else have info. on this?

 

The mm bore is what changes the quad from a 660 cc to a 686 cc. Stock bore is 100mm 686 bore is 102mm. You get the existing sleeve bored to 102mm to accomodate the 686 11:1 compression or 12:1 compression piston. You can also buy a stock bore 100mm 11:1 or 12:1 piston for your quad. I'd have the mechanic hone the cylinder to proper clearances for the new piston wether you choose to go to the 102mm bore or stay stock bore. I'd also reccomend the Ross piston or somthing other than JE. I've personaly had two pistons fail on me. Working on the 3rd as we type, I'm a glutton for punishment I guess. LOL. You need dual rate valve springs to use the stage 2 cam also. I would not run pump gas even with an 11:1 imo.

 

Thanks wshrdskin. I've heard good about the Ross piston also. So what is the difference between the 11:1 and the 12:1? I know it's compression, but what is better?

 

The more compression the better your torque/power. But you have to run race gas with the higher compression.

 

If you're going to use the stage 2 cam, I'd go with the 12:1 or higher 13:5:1 Ross piston. The stage 2 cam is more of a top end cam and you'll lose a little on the bottom end. The 12:1 or higher piston will make up that difference and then some.