Engine noise

OK TT'ers, before you jump on my back...I spent the last two hours search this for help and I recieved a lot of information but nothing really touch my problem. 98 yz400, seems to be making a rattle type noise (not knocking or clunking), like something is coming loose. But where my problem differs is that it only makes it when the bike is warm or hot. Unusally 20 minutes into a good constant pace. NO real power lost, but I didnt pin it either when I heard the noise. Shut the bike down and gave it a look over, because of clutch work done recently (checking for leaks). When I fired it back up the noise was gone and everything ran fine while I took it back to the truck. This is the second time I heard the noise and both times were at least 20 minutes into the ride, but once shut off...it goes away. So this is far from a constant noise? Any ideas?

Is it a ticking noise? I've found that the crush gasket of the header pipe gets screwed up over time when servicing the oil filter. Because I have to loosen the pipe and rotate it out of the way, I think it screws up the gasket over time. When this happens, I notice that after the bike gets hot, it starts to tick (exhaust leak), but when it cools back down, the tick goes away. Also, the bike will spudder and pop on decel because of the exhaust leak.

Does sound like a ticking sound...I will check that. Like you said, I twist and turn that thing so much and it doesnt seem to have a tight fit...Will check...thanks

No problem. If you find that the exhaust gasket is the problem, or something else, please post what you find.


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