I think this one has the longer pin but I'm not sure. Do you know the measurment.

 

The one that broke was 55mm, the new one is 64mm. This piston is only a 101mm bore size, I've got another raptor with a stoke bore 11-1, I'm hoping that one don't break? Will find out soon, both bikes will be torn down because of yamahas famous 01 tranny!

 

I just orderd a 105mm JE piston. The JE rep said it is going to be two weeks before I see a piston because they are redesigning the pistons, but he didn't know what exactly they are changing. Hopefully they get it right this time.....

 

The pin in this one was a 55mm pin. What octane gas was you running in yours FireFly when this happened?

 

All this JE piston stuff scares me. Broke one (JE makes the YFZ GYT-R 13:1) and have another in right now that I'm not expecting much life from.

 

I'm heading out to Gordens well today and have decided to mix some C12 with my 91 octane. I don't know if I will feel any difference, but maybe it will keep me from having any problems. I know I will see a difference when I can get ( have to have the $$$) Those 35 FCR's and sixsixt's intake put on.

 

I think my buddies JE may be cracked around the wrist pin too. 12:1 stock bore with about 7 hours on it.

We dragged about 300 yards twice went to line up again and he lost power. Still ran but its shakin the wheels off the ground on revs and has oil all over the back of the motor, We are gonna tear into it tomorrow.

 

I run sunoco 110 mixed 50-50 with 91. The octane rating doesn't make a difference unless your running lean, in that case the piston would have denotation marks on it. Mine just broke in a criss-cross pattern with a small piece out of the middle.

 

Looks like a manufacturing defect too me.

 

Well thanks for the great info. I was debating on the GYT-R HC piston but i think all of this contrivercy my mind has changed.