Crankcase pressurized '72 combat

Was gassing up a mile from home and noticed an oil drip, a steady one, oil level was a little low. Got home and and the leak was worse. Got it on the lift and no obvious leaks but the area around the junction block that's mounted to the case was oily and really the only suspect area I could see. So I undid it checked the hoses and clamps, put in a new gasket, topped The oil off and started it up. Went to make sure oil was coming back to the tank and w hen I took the cap off an air/oil pressurized mix was spewing out. Lots of air in the oil. The oil tank was full to the neck. Drained some oil from the tank and started up again. This time I could see the oil returning to the tank but it was still somewhat air saturated. Then I noticed oil oozing out between the crankcase halves wiped it clean and I could clearly see it oozing. Obviously the crankcase was pressurized.

Being its a '72 it's got the suspect breather but I have that plumbed to an xs650 reed valve. Oil pump might have starved after I took off the junction block but I poured as much as I could down the pipe
.? My plan now is to remove the breather, hoses, xs650. Any suggestions about what might have caused this and possible remedies appreciated. Thanks, rick

Maybe there is a kink formed somewhere in an oil line. Inspect. Easy enough to check oil pump pressure simply undo rocker feed and pressurized feed should be apparent , have rags handy.

Where does your oil tank breathe to? How long have you had this set up?

Oil tank breathes to a catch bottle next to the battery. I've been running this setup for over 5 years and 7000 miles the catch bottle has always been mostly empty. I'm away for a month so I can't tear into it. Just trying to gather some ideas. I'm sure as I get into it the culprit will reveal himself. As I write this I'm realizing I'll have to pull the primary inner to replace the crankcase seal which surely has given up the ghost. I'm too old for this shit! Ironically i had posted the bike on Craig's list and received two solid offers the week before this devil showed his face. Thanks for any input, rick

Your timed breather disk may have it's ears sheared off and is stuck in the closed (or partially closed) position, where a reed valve can't help.

Also, are you sure you plumbed the pipes correctly? If all the oil is in the tank, you are starving the engine and risking major damage.

I feel your pain on the "devil showing his face". We just posted Sally's '02 Trailblazer on craigslist and the NEW battery is dead when an interested buyer shows up! 2 days later, I swap out the battery, take it to the carwash and wash it up nice and tidy, another buyer shows up and the bloody brake safety relay won't disengage the transmission lock!

Crikey...

rgrigutis said:

........... Ironically i had posted the bike on Craig's list and received two solid offers the week before this devil showed his face. Thanks for any input, rick

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..... I had a buyer across town for a 72 Chevy pick up truck that I was selling back in the 80's, He said he wanted it for sure but didn't have a way to get over to me. So, I said that I would go ahead and bring it to him, went out and turned the key and it wouldn't start (350 V-8 never had a problem) took the air can / filter off and had my Dad crank it, damn thing back fired out the Holley carb and started on fire. Also Had a Honda NX 650 (great bike lots of torque) again no problems prior and had ridden it the day before after getting home from work, prospective buyer calls and says he's coming over, I go out and hit the button and it won't start....go figure. Cj

The fact that oil spewed out of the oil tank when you removed the filler cap is proof positive that the tank vent is blocked. Clear the vent, then report back.

Slick

grandpaul said:

Your timed breather disk may have it's ears sheared off and is stuck in the closed (or partially closed) position, where a reed valve can't help.

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Timed breather disk? Do they have those on a 72?

swooshdave said:

grandpaul said:

Your timed breather disk may have it's ears sheared off and is stuck in the closed (or partially closed) position, where a reed valve can't help.

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Timed breather disk? Do they have those on a 72?

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No.

Ah, so.

Update. I took everything apart from the breather to the oil tank, including the breather and xs 650. No blockages. Ran air thru the breather line of the oil tank, no blockage. After disassembly of the breather I noticed no foam baffles. Called Ella over at old Britts to order the foam baffles and figured I'd ask Fred about it. I'd forgotten about the '72 breather situation w/sustained high rpm operation. As we were talking the light came on! I'd just come off the interstate after a 30 mile 75 mph run and the breather couldnt breathe , pressurizing the case. I hardly ever ride this bike on the interstate. It's my backroad twisty turns bike. I hadn't run it in a month and figured a high speed run would top off the battery. Anyway with the temp in the 70's yesterday I fired him up and took one of the twisty routes around my home for about an hour. No leaks! When I put it back together I installed a clear plastic hose from the breather outlet to the xs 650 inlet. There was a small wispy film moving thru the clear hose. Looks good to me

Thanks for your input and until next time and we all know there's a next time right around the corner

My pressurised cases were due to a blown out head gasket between pushrods tunnel and bore

My pressurised cases were due to a blown out head gasket between pushrods tunnel and bore

The Comnoz reed valve breather that fits onto the bottom of your crankcase would be a good replacement for the original camshaft breather.

chasbmw said:

The Comnoz reed valve breather that fits onto the bottom of your crankcase would be a good replacement for the original camshaft breather.

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These do not apply to the 72 crankcase and no camshaft breather on the 72.