General Category > General Discussion
Over pressurized crankcase Cal III
Vecchio Lupo:
Gentlemen,
I have been a Guzzi guy for 40 years but this is a problem Ive never had. Perhaps you can help. I dragged home a running (poorly) 1990 Cal 3. It had a huffing left side head gasket and a slipping clutch with oil drip. I replaced rear main seal and clutch stuff, then 2 new head gaskets. Oil tight, runs and shifts great. Decided to ride to Jacksonville from Charleston.
Running on I 95 south at about 80 mph, I stopped for gas at the 175-200 miles mark….i noticed oil from breather tube and what a mess. I checked oil, low-ish but not bad. I slowed to 60 and completed my run. Engine making a wheezing ( not a knock) noise and most oil gone. Trailer back to Charleston and tucked away.
Now, after filling the oil and leaving sit…floor is dry so no leaks. Bike would start but wheezed and bumped in uneven sounding roughness. I’m thinking clogged pvc/ breather valve, or worse a broken piston ring allowing severe over pressure. Or maybe a compromised head gasket but that wouldn’t pressurize the case?
Does the collective have ideas differently from stated?
I’ve started to tear down the left side just now and will break down the rest tomorrow. Just looking for ideas…thank you
acogoff:
I wonder previous owner messed with the breather system, the older ones had a check valve or ball in the system.
Maybe it was lost.
pehayes:
If the cylinders/pistons/rings/valves were all in theoretically perfect condition there would never be any pressure build up in the crankcase. Yes, during each cycle of the crank there are periods of slightly increased internal pressure and slightly decreased internal pressure. Pistons are rising and falling at differing times and rates. The net effect is a zero sum equilibrium after the cycle is complete. If you have an excessive buildup of pressure then you know where it is coming from. Sorry. Time for serious wrenching.
Patrick Hayes
Fremont CA
John A:
What may be happening is the ball check valve in the large hose on the top of the bellhousing is sticking closed. I was cooking down the road on a Cal2, my wife following on an Ambassador as we went home from an Oklahoma rally, ‘84. It suddenly dumped almost a quart of oil out the breather drain onto my wife. I luckily had rerouted the drain from the air box to overboard so it didn’t fill the air box. Then it took some looking to find the problem because it would do it randomly , just puke out almost a quart. What was happening is if the ball check closes off at roadspeed, the oil is forced backward up the oil drain tube in the crankcase until the end of the drain tube is out of the oil. It should be submerged . There was a change to that ball check valve so that it couldn’t completely close. If you look at the ball seat, the updated valve has a square outlet and the old ones had a round outlet the ball could seat in. You can use a file to modify it. I’d look for a problem with that valve .
guzzisteve:
--- Quote from: acogoff on February 05, 2025, 07:31:29 PM --- I wonder previous owner messed with the breather system, the older ones had a check valve or ball in the system.
Maybe it was lost.
--- End quote ---
THIS, before pulling motor all apart I'd pull airbox & look in the larger pipe going in bell housing, metal steelie stuck
John beat me to it
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