Leaking Exhaust Valve on CB450

[ericfreeman]

I have a customer who brought his late model CB450 to me to get it running properly. He said another shop did a compression test and got 160 on the right and 60 on the left. I checked the valves and could not get a .001" feeler gauge in any of the 4 valves. I opened the clearances a few thousand for testing and ran a leakdown test. Left is 90/72 while right is 90/87. There is noticeable air coming out the left tailpipe so the exhaust valve is obviously leaking. Can the head be removed with the engine in the frame or does it need to be removed? Just gathering info at this point so the owner can decide what to do next. Thanks for the help.

Eric

 

[ancientdad]

No, the head can't be removed in the frame (unless you cut the backbone of the frame and re-weld it afterward).

I'm sure it doesn't run well ATM but a little bit of riding might improve things as long as the exhaust valve isn't actually burned yet.

 

[ericfreeman]

Thanks for the reply. I figured the engine would have to come out but wanted confirmation. I agree that running the bike could help, especially if there is carbon on the valve face. I'll know more after running a compression test when the new battery arrives.