Topic: 1975 CB400F Still Leaks oil at the head gasket

[Mainer4]

Ok, I took this bike from a non running cylinder seized backyard castoff to mostly rebuilt and newly painted.  Fast forward three years.  After 600 miles it is leaking oil at the cylinder head.  Retorqueing the head I found that two bolts (the extended ones) were loose.  600 or so more miles, starts leaking again.  Retourqueing this time does not help.  Keep in mind all gaskets and o rings were replaced (Vesrah kit) in the head.  There is no damage to the cylinder head mating surfaces.  Now someone mentioned to me to try a Cometic gasket, but I can't find any listing for CB400F in their on line catalogue.  Seriously appreciate some advise because I can't ride the bike with any satisfaction with oil getting over everything each day I ride.  I love the bike other than this annoying problem and with only 24K miles on the clock  I was hoping the keep this a long while.  Any recommendations for a new head gasket supplier?
 
Howard in Maine.

[wingman]

Are we talking a light weeping from the headgasket or a serious leak, blowing oil all over your pants? 

[camelman]

Howard,

I have a funny feeling you need to get that head checked for warpage.  If it is leaking after a few hundred miles, then something is wrong beyond just the head gasket.  Running it through thermal cycles with two bolts loose could have caused it to warp, or it might have been bad before.  It can be removed with the engine in the frame, and spot checked easily enough with a good straight-edge, or have a machine shop check it.

You'll have to pull the head regardless to replace the head gasket.  The head gasket is going to cost you about $35 shipped, and a decking job should only be about $60.  Taking off 3 mil will have a slight CR increase too, so you might notice a bit more umph at lower RPM.  Here's the impact of taking off head material to remove warpage:

stock CR - 9.4:1
0.003" - 9.54:1
0.005" - 9.63:1
0.010" - 9.87:1

Camelman

[Mainer4]

Are we talking a light weeping from the headgasket or a serious leak, blowing oil all over your pants? 

I am talking blowing oil all over my pants, and other more important stuff like motorcycle frame, cover, rim, etc.
Seems to be coming just from the left side this time.