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Hi, i have a problem with my CB350. It's leaking oil from the head.
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I think it could be a blown headgasket, but i'm really not excited about taking out the motor and replacing it. Also i have good compression.
Another thing i came across was this:
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This is the bolt right under the spark plug. It seems like it is loose, but i can't manage to tighten it or get it out.
Could this bolt be the reason for my leak? How do i replace it, is it just to force it out? And what should the torque be?

I also tried to tighten the head, but it was already tightened to the correct torque. Could i try to tighten it more?

And if i have to replace the headgasket, is it hard too do?
 

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Your head gasket isn't actually "blown" or you'd be losing compression, but it is leaking oil which is not uncommon. The bolt under the spark plug has been over-tightened by someone previously and they stripped the threads in the cylinder casting, so they attempted to use a longer bolt with a nut underneath. The engine has to come out of the frame to tear down the top end for the repairs you'll need to do. Re-torquing the head will not likely stop your leak.

Since this is your first post here, you need to start here first
Critical - READ BEFORE YOUR FIRST POST
 

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As mentioned, it's a common problem with a lot of different Honda's (and a few other manufacturers) The o-rings sealing oil passageget hard from the heat cycling then distort and leak. Some bikes are worse than others, CB550 has unsupported o-rings which leak around 7~10,000 miles when ridden hard, I did o-rings and gaskets sometimes twice a year on mine after the 591cc conversion. CB350 isn't generally too bad for leaking in that position so maybe head /block wasn't checked for flatness or o-rings were not changed or the wrong material was used? (cheap aftermarket stuff?) It's a PITA pulling motor but not actually difficult to do. Have block Helicoiled or 'Timesert' installed on both of the 6x1mm threaded holes.
 
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