engine oil leaking into the primary

Hi group,

I've got one issue remaining that has been bothering me for the last few years. Oil is getting into my primary through the crankshaft seal on the drive side. Just to zero in on the responses.
- '72 combat 750 with modified breather 850 style and one way installed inline back to the oil tank so negetive crank pressure
- have replaced the crank seal several time - no joy.
- draining the wet sump oil before starting doesn't stop the problem
- notice the end float on the crank seems excessive
- engine bottom end has 21K miles since rebuild (superblends)

What do you think?

Thanks,

David

If you are losing gear oil, you may need to install a clutch rod seal Got mine from British Cycle Supply Company www.britcycle.com Part # 04-373/A about $25. Jerry

72 Norton Combat

If it makes you feel any better, you're not the only one. The previous person to work on my 750 had staked the crank seal in three places and smeared epoxy over the outside. I didn't bother doing that and haven't blown any seals but I do notice the ATF looks brown whenever I change it so I suspect I'm getting some leakage too.

You could try fitting a Maney crank seal. They're said to be better about leakage.

Debby

You might try the Chicago Rawhide #12343 crankshaft seal. It has a long life lip. I noticed some improvement with this. Once I installed the XS breather valve I had no more leaks. I had tried the Motormite brake check valve with poor results. IMO, the Norton needs a reed valve. Automotive PCV valves don't work either. The XS is very inexpensive, $16.

It may not be the seal, there are 3 bolts that fix the inner primary to the carnkcase, they are stopped from undoing by tab washers so they can loosen off slightly but everything looks to be in place. I found mine loose when renewing the gearbox mainshaft seal and there was evidence of oil seeping in through the bolt holes through the threads.

I agree regarding the reed valve and may go that way. However this engine didn't leak at all for the first 7-8 years after the rebuild even with no one way system. I'm ruling out wet sumping blowing the seal since I drain off the sump before starting. I don't understand why a new stock seal won't work, must be something else going on. I'm thinking the crank end float may be disrupting the seal...any comments on that?

The three bolts holding the inner primary to the crankcase are tight and have new tabs.
I'm not getting gear oil from the gearbox in the primary - have Dyno Dave's seal already. The oil getting in is definitely engine oil and the primary gets too full then leaks out the gearbox shaft felt seal (not really a seal) from the spray of oil getting into the primary chain. I don't use ATF in the primary.

Thanks,

David

Those 3 bolts should have thread lock on them to seal the threads.

I found that a smear of Loctite (which one? bearing seal? Can't remember) on the seal cured the leak. A new one I fitted without the Loctite leaked like a sieve.

My friends 850 went through this as well. In the end, I believe that the problem was simply wet-sumping and the resulting pressue that it caused. We drained the oil out and all that and it woud come back again. If memory serves, the oil was getting past one of the bolts

We put an anti-sump valve in and the problem went away.

I know you said that you didn't think sumping was the problem but I I would try the cheap fix first.

Just replaced the crankshaft seal again. Someone recommended the all rubber type - I've been using the type with metal outside. While using my pry tool, noticed the old seal was a pretty loose fit in the crankcase. The all rubber one went in tight - so hopefully this was the problem. Already put a motormite brake valve in several years ago, so getting some negetive crankcase preasure. Also just replaced the points seal and timing side crankshaft seal, so hoping to eliminate all leaks. The engine was oil tight for the first 7-8 years after the restoration - 25,000 miles later and 12 years. Need to take it out tomorrow (Saturday) and run it hard.

Maybe a scavenging problem? Are you getting a good air-oil mix spitting into the oil tank? The return gears are unprotected. Check oil pump teeth and also the passageway to the sump as well as the sealing surface on the pump face.

Already put a motormite brake valve in several years ago, so getting some negetive crankcase preasure

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Unfortunately, you do not have negative crankcase pressure, you have a pressurized crankcase. I consider the Motormite more of an urban myth than a PCV valve, it is effective for a few hundred miles, at best. This issue has been addressed many times here before. If you missed it, the cure for a leaking crankshaft seal is a reed valve crankcase check valve. I've had very good results with the Yamaha XS PCV valve. CNW offers one as well, which is said to be even more effective. Once you install a reed valve your oil leaks mysteriously disappear. Once the crankcase pressure is eliminated the crankshaft seal will function to keep things out of the bearing and crankcase rather than keeping oil in.

I've had exactly the same problem recently and also put it down to the pcv. I've gone belt and braces and fitted the Maney rubberised seal but don't think there was much wrong with the old seal.
Mines a Krankvent, you can hear it operating at very low revs. I did notice this time round that it had gone a bit. Not long after, the clutch started slipping a bit that's when I found the primary full of engine oil, next time I'll take the lack of noise as a warning.

No problems with the Motormite valve here and I've had it in there for about 5 years and 6000 miles. It has stopped my crankcase from leaking behind the cylinder ('72 Combat). A lot of these are out there being used successfully. I just bought a spare for $3.99 at Pep Boys just in case.

You mentioned that you relocated the breather. Did you do the scavenge/pickup modification to the case as well? Being a '72 with the scraper flange over the scavenge hole in the cases, you may be "wet sumping" when you are running it hard. Many experts theorize that this flange will prevent the oil from reaching the pickup at high engine speed and cause cavitation of the scavenge side. The "wet sumping" at speed could cause some crankcase pressure that the Motormite flapper can't overcome.

Just food for thought.

Engine oil leaking into the primary case may not be due to any sort of crankcase pressure problem? But may only due to oil seeping past the seal-if the engine oil has drained down to the sump, part or all of the crank seal will be below the level of the oil.

Hi JimC wrote:

Unfortunately, you do not have negative crankcase pressure, you have a pressurized crankcase. I consider the Motormite more of an urban myth than a PCV valve, it is effective for a few hundred miles, at best. This issue has been addressed many times here before. If you missed it, the cure for a leaking crankshaft seal is a reed valve crankcase check valve. I've had very good results with the Yamaha XS PCV valve. CNW offers one as well, which is said to be even more effective. Once you install a reed valve your oil leaks mysteriously disappear. Once the crankcase pressure is eliminated the crankshaft seal will function to keep things out of the bearing and crankcase rather than keeping oil in.
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Just wondering how you know my engine has positive crankcase pressure without seeing it. Just went on an enthusiastic 378 mile ride and the primary didn't gain any oil. The new all rubber seal seems to have cured the problem. The points seal still leaks, however after just replacing it. Suspect the seal has been sitting on a shelf for a number of years are various closed shops and by the time it got to Rabers it's no longer that pliable. Anybody know a source for new seals for the points?

If you have one to match up you could try these guys.

http://www.bearingengineering.com/

Just wondering how you know my engine has positive crankcase pressure without seeing it

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From reading your posts. You have oil coming out of both the crankcase and the timing chest. That's a pretty fair indication you have a positively pressurized crankcase. What do you have for a PCV valve? What ever it is, I doubt it's working. If you stop to think about it, with negative pressure in the crankcase, you could probably run without seals if it weren't for outside contaminants.

12 years... 25,000 miles... some wear causing increased blow-by and increased pressure in the cases that the PCV valve cannot overcome...

7-8 years and no leaks... blessed!

The reed valve works so much better... But I did run my 70 Triumph T120 with PCV valve for 3 years 16,000 miles and no issues