Topic: Oil Coming from Cyl Head

[Heirborn]

The bike is a 1970 K0. Rode the bike last weekend about 25 miles on the highway. Bike runs great, no problems. When I got to where I was going, got off the bike and the engine was a mess with oil and the right side cover was a mess too. How my leg was not soaked not sure, other than is was not in the direct line of oil coming off the engine. I cleaned it up and rode it around town with no problems. Headed home that Sunday and kept an eye on it. About a 1/3 of the way into the trip I noticed drops of oil forming on the rear of the fins, right side. By the time I got home it was a mess again. I have not been able to determine exactly where it is coming from.I  Rode the bike here locally yesterday and did not have any problems. Very short trip and not at highway speeds. Any ideas where it might be coming from? I suppose pulling the motor is in order?

[ekpent]

Well don't pull the motor till you isolate the leak. Places to start looking is the head and base and valve gasket obviously. Also look where the tach cables enters the valve cover. Make sure the breather hose is hooked up in the top back of motor.Clean the motor well and keep an eye on it. Some guys have isolated leaks by putting talcum powder or such on the engine to locate the leak.Does it seem to happen worse at high load rpm highway speeds etc.  ?

[rklystron]

Right side cover. You mean the cover that covers the oil tank? If so you should check your oil level. When you do this put the bike on the center stand. Warm the bike up to operating temp and check the dip stick. There is a good possibility you have to much oil in the bike. Also check your breather tubes to make sure they are not clogged or crimped. You have 3 to check. Top of the engine on the valve cover, the breather on the bottom of the engine next to the swing arm and the breather coming off the oil tank. If they are not the problem you may have an issue with the oil pump. Can you check the oil pressure coming off the oil gallery? The pressure at start-up should be around 60psi.

[Heirborn]

So, the best I can tell oil is seeping from the head gasket right under the exhaust flange on number 4.

I'm afraid that if I try to tighten the head bolt at the number 4 spark plug well, to see if that will help, the bolt will snap. Safe assumption? 

I found a thread that spoke of the seeping/weaping gasket and that it's pretty common.  A "simple" fix is to take some cotton rod and stuff between the fins to soak it up and replace as needed. I have a ride coming up and not quite ready to pull the motor.

[Johnie]

Some guys will stuff some 1/4 inch nylon rope between the fins which works good too.

[mongadillo]

I just finished a Cylinder Head gasket replacement on a 78 CB750F2.  You can't tighten the head bolts without pulling the engine, they are located under the top tubes of the frame and you wont even be able to take the head cover off with the engine in the frame (sorry). 


If you decide to do the job I recommend Mike Nixon's Book on replacing the Cb750 Head Gasket, it's really a very helpful guide when used in conjunction with the Service manual. 

The Engine and Transmission come out as a unit, its a lot of work, but in the process you can get the heads serviced, new valve guides, seals, etc. 

Good Luck. 

PS - The Cylinder Head studs WILL snap if you over torque them, I snapped one, do not exceed 14ft/lb. Get a reliable torque wrench, preferably 3/8" drive.