KFX400 valve train noise???

[mad440]

Hey guys i need some help diagnosing this problem, this is my brothers KFX. The issue is there seems to be excessive valve train vibration when the bike is rev'd up? Idle it sounds fine even up to half throttle but once you mash on it this noise comes from the engine head/valve area that just sounds wrong I wish I could describe the sound but the terms escape me right now, any ideas would be great on fixs, only things i can come up with are valves are out of adjustment or the rockers are sliding back and forth on the shafts at high revs causing this noise, do they make a shim kit for this? My ex never made such a noise so this is a new issue to me. Thanks for the help!

[nyates450]

Bike doesn't have rockers. It is a shim and bucket design. The valves don't ever get loose. They tighten up as they wear. The noise is most likely a worn cam chain.

[mad440]

Thank you!! I will look into these solutions, looks like the bro is going to have to invest in a service manual if he wants me fixing this.