cylinder head oil blowbycylinder head oil blowbyadjusted valves recently and the cylinder head cover breather hose is letting out oil. would a tappet clearance of less than 0.1mm be causing this?
Typically blowby is a result of combusttion pressure getting by the rings and crankcase pumping that is caused by the pistons moving up and down. Also, there are volatile components in oil that come out when the oil gets hot and these will condense as they cool as they exit the breather. There will be a small amount of pressure in the crankcase, even when the rings are working perfectly, so some oil out of the breather hose is normal under the best circumstances.
Another factor is the oil that you are using. I had a CB400F back in the '70's that ran really hot and always left a few drops on the garage floor, from the breather hose, after a hard ride and it would always use some oil between changes.. I was running 10w40 Casterol at the time. I had always run Castorol GTX 20w50 in my 305 racer and had no problems with it, so I changed the 400F over to the 20w50 and the spotting stopped and the oil consumption all but disappeared.
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