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SOHC.co.uk Forums => CB350/400 => Topic started by: the-chauffeur on June 26, 2011, 05:14:35 PM

Title: 350 twin head gasket seep
Post by: the-chauffeur on June 26, 2011, 05:14:35 PM

I'm still in the first 1,000 miles after rebuilding the 350 K0 twin, and I can't seem to clear up what appears to be an oil seep from the RHS of the head gasket. The top end is pretty much tight, and it certainly isn't blowing, but every time I give the bike a good run out, I return to find traces of oil on the top fin or two of the cylinder block right hand side. I should add that for a short while, I had a leak from the tacho seal and earlier it suffered from sealing washers that weren't on the top of the engine. Must've been like it for a month or so (which I originally thought was caused by the head gasket) but stopped immediately when I replaced the seal/replaced the sealing washers.

My question is, are the 350's known for leaking from the head gasket, or have I just saturated it with oil from the tacho joint? I know the oil feed to the head is on the right, and I'm wondering whether that's a known weak spot. I'm guessing it could be old oil drying out from the gasket, but I'd've thought that would've dried out within twenty miles or so with a hot engine.

Or should I just wait another few hundred miles before I start worrying about the oil traces . . . ? Meanime, I'm considering trying to find a set of heavy duty engine studs - any good sources out there?
Title: Re: 350 twin head gasket seep
Post by: PatM on June 26, 2011, 05:18:18 PM
Sounds like the o ring is leaking on that side/feed?
Title: Re: 350 twin head gasket seep
Post by: the-chauffeur on June 26, 2011, 07:58:03 PM

Thanks Pat - although I'm not quite sure what o-ring you're referring to. 

The only part between the cylinders and the head (other than the gasket) is a dowel - hence the original question as to whether 'they all do that, sir' or not.   :P
Title: Re: 350 twin head gasket seep
Post by: Bryanj on June 27, 2011, 05:28:15 AM
Aftermarket gaskets were a bit notorious on the 250/350 as they arrived "dry" whilst genuine Honda ones were "sticky" and arrived with paper on each side
Title: Re: 350 twin head gasket seep
Post by: florence on June 27, 2011, 09:06:38 AM
I would wait and see it develops, it could just be left over from the tacho drive.  I've had one of these for the last twenty five years and they always seem to leak oil from somewhere at some point.  As soon as one leak is eliminated, another emerges.  As with all oil leaks, unless it's coming out in pints, I wouldn't worry too much, it all helps to keep rust at bay.
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