Can you tell the compression ratio by the numbers on the piston? Mine has 101p on the inside.

 

the number 101 should be the bore size. don't know about the p.

 

Its supposed to be a 100mm piston and 10:5:1 compressiom ratio. Just wondering if the 101 meant 10:1 compression.

 

Where did you get your piston and how much did it cost you? I am looking into getting a piston. Is it the stock bore? thanx

 

These pistons can be purchased from about any of the high performance engine people, they are Raptor pistons, and will drop into the 660 Grizzly if you use the standard bore of 100mm. The 102mm is .20 over standard, I believe, and you will have to bore your cylinder, and with the 102mm piston will give you 686cc. Trinity Racing, Curtis Sparks, HMF Engineering, and Four Stroke Tech, and Powroll sell these pistons, to name a few. 11:1 seems to be the most compression the Grizzly guys are going for, I've heard of pistons that will give you 11:9:1 and 12:5:1 , do not think you want go that high, unless you plan on using some racing fuel. Hope this helps.

 

actually the 102mm is .080 over standard size. if you look at sparksracing.com it tells you how big the 102mm piston is. i just ordered the je 102mm 12.5:1 piston for my raptor, also a mid-range cam and hd valve springs from sparks racing. [img]i/expressions/face-icon-small-smile.gif[/img]

 

That makes sense as .20 over will not give you 686cc, have ordered a mid-range cam from Web Cam to go with my 11:1 piston, and HD valve springs.