knocking after new top end

[cr250dave]

I have an 03 cr250 that I just put a wiseco piston in. It starts fine and idles good but when going to start breaking it in I noticed that there is a knocking noise after I roll off the throttle. It only does it when the rpms start coming back down and it is not consistant. I will knock a couple times and then stop. I was real careful during the install and did it all by the book. Any advice would be great.

Thanks,
Dave

 

[ellandoh]

possible lean condition????

 

[cr250dave]

You might be right I will check that out. Any other ideas??

 

[bclapham]

sounds like an air leak- maybe buy another base gasket and double check the sealing surfaces.

check the manifold and carb is bolteted up OK also.

 

[Sandy Whoops]

Did you happen to change your premix ratio for the break-in? And is your gas fresh?

 

[cr250dave]

Pre mix was the same and new gas. I richened up the needle and the main jet and took it out today. It sounded great I thought I had it rich enough before but I guess not. Anyway thanks for the help guys its all broken in now.

 

[Pete Payne]

sounds like it could be a lose heas stay or motormount . They tend to onlyvibrate on the decel when loose .