Piston on exhaust side

Fast6hand

Active Member
Oct 10, 2013
2,022
308
145
West Palm Beach
So I pulled my motor today. I'm going to do a leak down test. Yes I know I didn't need to pull the motor but I did for learning purposes. Anyways, I took a look inside the exhaust port at the piston and noticed it was a coffee color. The intake side however was not. Is it suppose to be that color? Or is it a burn mark from maybe running lean? Or is it just build up from the exhaust? And how do you clean out the carbon build up without getting it in the motor, without pulling the jug off? Thanks
 
Didn't check compression. When I bought the bike the guy told me it had been bored out and had a wiseco piston. I found these serial #573M06675's on the top of piston. Matched numbers to wiseco 66.75 which I believe is .030mm over STD. He said it had about 5 hours on it. There wasn't even any carbon build up on top of piston. I guess I just wanted to make sure some small scratches were normal along with the color.
 
Didn't check compression. When I bought the bike the guy told me it had been bored out and had a wiseco piston. I found these serial #573M06675's on the top of piston. Matched numbers to wiseco 66.75 which I believe is .030mm over STD. He said it had about 5 hours on it. There wasn't even any carbon build up on top of piston. I guess I just wanted to make sure some small scratches were normal along with the color.
66.75 is 0.75mm over the standard 66mm bore.