Hi
I have a 1993 CBR, it has 27,000 miles on it. Always has fresh oil in it since new. When the engine is cold it sounds good nice and quiet. When it warms up or is hot there is a knock. It's not real loud but it has been getting a little worse.
Is this common on these bikes ? I have a feeling it may be a rod knock not sure, and I can't imagine a worn out rod bearing with this few miles on it and never raced.
Could this be a valve adjustment ? I would think a valve tap would be there regardless of operating temp.

Any thoughts very much appreciated
Tom

 

I agree that it's probably not rod knock. Way too few miles for that. Valve tap is the more likely culpret. Remember that these are all aluminum engines. As the cylinder head heats up, it expands. As it expands it actually causes the valves to get pulled further away from the cams, and opens up the gap. That's why there is more noise when its warm and not cold. When was the last time the valve clearances were checked ?

 

IDODIRT
Thanks for the reply. I realy didn't think valves could get worse as they warmed, this is encouraging. I will check this week. They have never been adjusted, the engine has always been quiet. Is this a big job to check ? Would you know if there adjustable or shimms ?
Thanks Tom

 

I'm sorry to say, it's shims . It's not a easy job to do, but well within the realm of someone that's mechanically inclined. It will probably take all day to. Not because it's hard, but there is a learning curve that you go through and you're double checking everything. I don't trust shops to do this. I guess I'm jaded.

 

OK thanks I can handle it. Just need to find the shop manual and roll up my sleeves.
Tom