frothing oil in the tank

maylar · Jun 12, 2012

A buddy has a 72 Combat Interstate and the oil in his tank seems really bubbly. I'm not sure if this is normal or not, but it sure looks odd to me.

This is after having serviced his oil lines and replacing hoses and clamps to fix a leak. He also mounted one of Mike's XS breather valves up near the tank. His breather hose is taken from the timing chest where the later 850's are, a modification that he did years ago.

Has anybody else seen frothy oil bubbles in the tank?

pete.v · Jun 12, 2012

This will generally occur when going on short trip, ten to 15 minutes, and not get the oil good and hot. You need a good half hour run to come up to temp. Don't be shy, let er fly.

With the valve mounted near the tank, getting the oil hot is even more important because the cooling of the valve itself can promote this condensation effect. This is why some mount the valve right to the cases. If you were coming from the timing chest, this would be ideal.

When mounting at the bottom of the crankcase as with a 72, I feel too much oil can get into the reed so mounting it higher is what i would do. Some drill a hole in the valve somewhere (swoosherroony) to allow oil to drain back, but this is really too late for this. Blow a tune on a saxaphone. Now fill your mouth with pancake syrup and try it again. Oil in the reed valve defeats its purpose.

More effective installations of the valve does not negate the need to get it up the temp. So no matter what you do, you still need to let er fly once in a while.

I do not mean to rude but I think this is where the CNW mod just dos not make good sense along with other who mount the valve down there. Having the internal 72 cases modded and the scavenge moved back, as some do, would be its saving grace to a point. Sorry Matt, no offence, just my opinion. Loved ya on TV.

OK, here we go. Yeeeeeeee haaa!

geo46er · Jun 12, 2012

Hi Maylar,
I can't say that I have seen frothy bubbles actually in the oil tank, but if you are referring to the whiteish water/oil scum from inside the breather line, yes I did notice that after I installed a one-way valve in the breather line. Which is why I do not vent my breather line into the oil tank.

Hi Pvisseriii,
I'll disagree with you regarding the operation of a metal reed valve smothered in oil, it should work just fine, in fact better. Consider those valves that Jim makes which install right on the very bottom. The trouble I see with such valves is that unless you are venting right back to your oil tank you will end up with an oily mess.

GB

rvich · Jun 12, 2012

My Combat has the XS breather valve near the tank. The condensation from the blow-by leaves the breather return looking like gray ice cream! Is that what you are refering to? Here is my understanding of what I am experiencing. There is enough blow-by on the rings to force gases from combustion into the crank case. This includes water vapor, which then cools enough by the time it gets to the tank to cause a messy looking, well... mess! I have been told that it will help get the breather closer to the cases. I live in a cool, damp climate which probably doesn't help either.

My present project, if I ever get it done, has the Comstock breather on the back of the cases. My Combat will get one too when the day comes to tear it down.

Russ

maylar · Jun 13, 2012

The frothing that we experienced was during initial startup, checking the oil level on the dipstick to verify that all is well. The bubbles add to the oil level in the tank and give an erronious reading there. We'll have to check again after a ride and see if it settles out.

rvich · Jun 13, 2012

That does seem odd. It's not getting a venturi effect at the chain oiler junction or something weird like that is it? When you compare it to your tank does everything look the same except for the frothing? Some weirdo kind of oil? Maybe an oil pump sucking air on the scavange side? The oil pump idea is kinda scary because it would suck to find out that you were pumping an oil latte to the head. I am just tossing out ideas.

Russ

xbacksideslider · Jun 13, 2012

Mufflers rust out because when they cool they suck moist air inside; same with water in engines and oil tanks.

So, run the engine long enough for everything, including the oil to get up to full temperature, and then run it some more, enough time at full temperature to allow any condensed water to become steam and escape by way of the breather hose to your air filter/intake or catch can.

Cook the condensation out of it.

cNw · Jun 13, 2012

pvisseriii said:
This will generally occur when going on short trip, ten to 15 minutes, and not get the oil good and hot. You need a good half hour run to come up to temp. Don't be shy, let er fly.

With the valve mounted near the tank, getting the oil hot is even more important because the cooling of the valve itself can promote this condensation effect. This is why some mount the valve right to the cases. If you were coming from the timing chest, this would be ideal.

When mounting at the bottom of the crankcase as with a 72, I feel too much oil can get into the reed so mounting it higher is what i would do. Some drill a hole in the valve somewhere (swoosherroony) to allow oil to drain back, but this is really too late for this. Blow a tune on a saxaphone. Now fill your mouth with pancake syrup and try it again. Oil in the reed valve defeats its purpose.

More effective installations of the valve does not negate the need to get it up the temp. So no matter what you do, you still need to let er fly once in a while.

I do not mean to rude but I think this is where the CNW mod just dos not make good sense along with other who mount the valve down there. Having the internal 72 cases modded and the scavenge moved back, as some do, would be its saving grace to a point. Sorry Matt, no offence, just my opinion. Loved ya on TV.

OK, here we go. Yeeeeeeee haaa!

You knew I would jump in on this....didn't you.

Well....maybe in theory as far as location. Fact is that the reed valve is not affected by oil whatsoever. If your bike wet sumps, it will actually return the oil faster, right through the reed, to the oil tank.

Now if you have some other kind of venting down low, I can see your point, but as far as the Jim Comstock designed breather....it truly is as good as it gets as far as efficiency and performance.

Also have to agree with all that has been stated about running the engine up to operating temp anytime its being used. Those that start their bike once a month during the winter season just to let it run for 5 minutes to circulate the oil, may be causing more problems than they know.

Glad you liked the TV show.....it was definitely a great experience.

Matt / Colorado Norton Works

maylar · Jul 4, 2012

I'm resurrecting this for an FYI of "what not to do".

It turns out that we had the 2 oil lines from the oil tank to engine reversed. A short ride to "evaporate the condensation" resulted in catastrophic engine failure. It's a heartbreaking lesson, this bike had been running superbly. Now there's a nasty mechanical clanking noise coming from the engine. I'm sick over it, as I was the one responsible for the hose routing.

Between the 2 of us my buddy and I have over 70 years of Norton wrenching experience. Now I feel like an incompetent noob.

Don't ingnore frothing oil in the tank if you've just messed with the oil lines.

Torontonian · Jul 4, 2012

My condolances...

Keith1069 · Jul 4, 2012

Between the 2 of us my buddy and I have over 70 years of Norton wrenching experience. Now I feel like an incompetent noob.

Feel for you. Reversed one way breather 3 years ago after cleaning out 'mayo' and rode 75 miles with no breathing at all and with engine normally very oiltight it pushed out through the crank oilseal and primary covering the whole left side in oil. Thing is it ran so well like that and was only when I stopped I saw all the oil. I have to check at least three times now that I've done the job right, whatever it might be, something on the car, bike or house.

comnoz · Jul 4, 2012

maylar said:
I'm resurrecting this for an FYI of "what not to do".

It turns out that we had the 2 oil lines from the oil tank to engine reversed. A short ride to "evaporate the condensation" resulted in catastrophic engine failure. It's a heartbreaking lesson, this bike had been running superbly. Now there's a nasty mechanical clanking noise coming from the engine. I'm sick over it, as I was the one responsible for the hose routing.

Between the 2 of us my buddy and I have over 70 years of Norton wrenching experience. Now I feel like an incompetent noob.

Don't ingnore frothing oil in the tank if you've just messed with the oil lines.

It can happen to anybody. The first Eccosse Ti that I ran on my dyno blew up on the first pull- because the MANUFACTURER had reversed the oil lines. That one cost some big bucks. Jim

rpatton · Jul 4, 2012

Nobody got hurt. The engine didn't do a radial auto-disassembly. Opportunity is knocking. Think of it as an excuse to build your dream motor. You can also think about drilling the vent holes in the timing chest so the 850 breather will work. Or better still, put in one of Jim's valves in any one of it's iterations and plug the timing chest back up.

maylar said:
This is after having serviced his oil lines and replacing hoses and clamps to fix a leak. He also mounted one of Mike's XS breather valves up near the tank. His breather hose is taken from the timing chest where the later 850's are, a modification that he did years ago.

frothing oil in the tank

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