clutch pushrod popping out and diagnosing case pressure


New Member
After several years away from this forum due to a well-running rebuilt CB350, I'm finally back. My clutch pushrod seal has popped out twice now, and luckily I've manage to catch it both times before I ran out of oil and ruined the motor. The first time I just assumed it was a fluke and tapped it back in, but after the second time I started reading up on it to see what could be causing it. Racers in particular talk about how it's relatively common between the small size of the seal, its poor retention, the thrust of the pushrod, and potentially high crankcase pressure.

I've ordered a new seal and some Hondabond, but I'm also trying to see if my breather tube is actually venting crankcase pressure. With the bike running, there is a very fine movement of air around the tube opening, but not exactly a steady rush of air. Is this normal or is my tube/valve cover plugged up? I'd assume with good rings there SHOULDN'T be a rush of air out of the engine, more like an exhale-inhale fluttering of air as the piston movement slightly changes the interior volume of the case.

Tomorrow I'm going to open the oil cap and send pressurized air through the breather to see what I'm dealing with, whether it vents through. In the meantime any help or comments on the issue are greatly appreciated.

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