What do you think?

[cr250dave]

Has about 20 hours on new piston. I was having what I think is piston slap so I tore it down and saw these marks. The jetting was almost spot on and the wiseco piston was properly broken in and always warmed up before ridden. What do you guys think I should do about this?? I also had a ton of blow by.

 

[oldfrt613]

Wiseco reccomends drilling 2 small holes where it rides over the exhaust port bridge, have you done this ?

 

[cr250dave]

Wiseco reccomends drilling 2 small holes where it rides over the exhaust port bridge, have you done this ?

Sure did. It is scuffed around the whole cylinder. While I am still a nub this is my third top end and this is the first time i've seen this :coocoo: What do you recommend I do about the cylinder?

 

[oldfrt613]

Is this a stock bore or replated cylinder ?

 

[oldfrt613]

If it has scuffed the whole cylinder, have you checked the ring gap ?

 

[cr250dave]

Stock with a wiseco piston.

 

[cr250dave]

Stock with a wiseco piston.

old ring gap is.356 mm

 

[oldfrt613]

If you can't "feel" any scratches, I'd deglaze it ( 320 grt ball hone ) and and use it. Be sure to check the ring gap. An unpleasant possibility is your lower rod bearing is going out, check it closely. I'd back off on the jetting to start to be on the safe side. You monitor what's going on with the piston without taking the cylinder off by removing the exhaust pipe and looking in the port.

 

[oldfrt613]

Wiseco recommends min gap .004"/in on the bore. Stock bore is 2.61" so you should be looking for a gap of .004 x 2.61 or .010" min ( I run my CR at .012" gap ).

 

[cr250dave]

ok will do. thanks for your input

 

[oldfrt613]

Always ready to help a fellow red rider ;)