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Honda 300EX Top End Problems

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Bought an 02 300EX that needed a valve adjustment supposedly. Has good compression but went to do it and it has 3 of the longer cylinder head cover bolts broken off in head. Also exhaust side rockers do not line up with the top of the valve stems. Not sure what's going on here, first time I've worked on this engine. I adjusted the best I could and turned it over by hand with the head cover off and after compression stroke the cam/chain would pop/jump but not skip teeth. Not sure what the issue is. I ran it for a while like that and am about to tear back into it just to see whats up.


I ran it for about 4 hours off an on with the noise getting worse throughout. From general top end noise then to that jumping noise getting more frequent to the point that I parked it. Performance wise it didn't seem to vary from start to finish. I don't have much into this so if it's going to be easier to just swap heads I'm going to do that and maybe a cam chain. I have a manual and it's not too detailed in troubleshooting top end noise. I have no micrometer but I'm curious of a way to check current cam chain to see if its at service limit. I have a home made tensioner tool so I could check that but I wasn't aware of any issues with the OEM one (unlike CBR f4i's :p).


Pictures from before I ran it:



Edited by Devil Tiger

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