Thanks for the info, sixsixT ...

I guess it varies quite a bit on different makes/models. I know my bike they said to run 93 and it is 11.8:1 from the factory. They said the same thing about the 12.5:1 models as well.... fuel injection is a different animal though.

I follow the octane talk pretty closely as it is always a topic of interest to me. The misconceptions surrounding octane captivate my puny brain [img]i/expressions/face-icon-small-smile.gif[/img]

 

I don't know Fox, I report you decide.[img]i/expressions/face-icon-small-happy.gif[/img] For hill shooting in the dunes I think 100 + or - to be safe.

 

I know what you meen thomez I think it's the same fore the YFZ. I talked to a rep from 76 and for a liquid cooled engine and a 4" bore he said 100 was good up to 14:1. Part of the problem may have been the carb bowls running low also even tho the seats were drilled and I'm sure it was jetted a tad rich. Some have suggested the piston could have been deffective. That's another reason for posting pics, to get some other opinions. I may also send it to a manufacturer to get an opinion on what might of happened.

 

I've got one of those je pistons that cracked. It's caused by the top of the piston flexing. Did you measure the legth of the wrist pin? Mine was 9mm smaller than the new one. I've talked to je about this problem, they want to see the piston. Other guys had new pistons sent to them. How much time was on the piston? Mine had about 40hrs on it.

 

I'm guessing about 20 or 30 hours.

 

Was it a stock bore or oversize? Call je and talk to them. A forged piston should last longer than that. I was pretty pissed when I found it broke, I am sending the piston back and bitching about it!

 

how was the bike running before you took the piston out? my bike is pressurizing the oil ressy when I run it hard and then when it cools I notice the level drops and drops. I know I am burning oil. I hope it is my rings so I can get a few more rides in. if it is the piston and I keep riding it Murphy's Law says I am sure to get stranded out at China Wall or Lizard hill [img]i/expressions/face-icon-small-sad.gif[/img]

 

102mm 686. The 9mm on the pin. Are you talking about the length of the pin? I've heard they made some pistons with shorter pins.

 

Blue he noticed some blow-by along with some oil coming out of the breather filter the last day of riding at Glamis on halloween weekend. And it was still running good, he took speed demon at olds while this was going on.

 

The smaller wrist pin is causing the piston to flex. I've heard they had alot of problems with the 102mm and the 105mm. the 9mm is the difference in the length between the wrist pins.