Need help with crankcase blowby

[qwispichkn]

Purchased a 1965 CA77. Rebuilt the carb tonight, set points and got it running. I'm getting a large amount of blowby through the crankcase. In a previous post, I mentioned that someone had installed a bleeder valve in the oil filler, which I should have known something was up.

After I got it running somewhat smoothly I opened the oil filler cap and am getting a huge amount of blowby. I have not done a compression test or bleed down test yet as I don't have the adaptor that will fit the spark plug hole. The engine does not smoke at all and appears to have plenty of compression when I kick it. I don't hear any odd noises or smell burnt oil. Will try to find an adaptor tomorrow.

Bought this bike for a winter project and was hoping I wouldn't have to get too far into the motor, and probably paid too much for it. Any ideas on how I should proceed?

Going to try to post a link to a Youtube video. Notice how the engine speeds up when I loosen the oil cap. Would appreciate any ideas. There is supposed to be a vent on the head cover, but I dont see a hose or the vent itself due to the frame being in the way.

https://youtu.be/xqdxEBOI3go

[Geoff Hastings]

That does seem a lot of blow by. There is a breather on top of the head that should have a pipe coming from it. When I first rebuilt my CA77 engine I had oil being blown out of this breather big time. Someone on this forum suggested I check the baffle plate (that sits under the top of the cam cover) was fitted the right way round. Turns out mine didn't have the baffle fitted, I removed a couple of engine bolts and exhaust pipes, tilted the engine down and fitted a baffle plate and gaskets the right way round. Since then, no oil is being pumped out and Iv'e done a few hundred miles on it with a nice oil tight engine. Might be that yours has either been fitted the wrong way round or like mine, thrown away so they blanked off the head breather and made the crankcase breather instead. The breather on the head is just about visible but not accessible without lowering the engine.