Comstock / NYC sump breather test

Schwany said:
That is funny.

It is a PITA even without the oil in there. Almost as much fun as changing gearbox sprockets.

How can you tell it is not the oil return returning the oil? Can you see the breather exit inside the oil tank? I have no idea what is inside an Commando oil tank.
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In a commando oil tank you can see what the scavenge is returning
And you can see what the breather returns
 
Schwany said:
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"How can you tell it is not the oil [pump] return returning the oil? Can you see the breather exit inside the oil tank? ...."

You can see it with a clear braided hose. I used a clear hose to check the very first experimental reed valve sump breather on my race bike back in 1985 and I could see the oil pumping up to the oil tank in jerks with each stroke (at low RPM). My idea was to help pump excess oil back into the oil tank to eliminate friction losses - and it worked (with a bit of development).

Ron Wood took a different approach - he installed two oil pumps with different pickup locations in his short stroke flat tracker.
 
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Comstock / NYC sump breather test


'tis a thing of beauty.
 
Nice feature that those sump breathers let the crank case pressure push oil back to the tank when the sump is full. :cool:
I guess that was the point of this thread. Dah! I limited my thoughts to the breather working great at reducing crank case pressure without blowing out seals.

I only have the pump oil return and a frothing cNw breather installed in the timing chest. Doesn't seem to slow the motor down any, and it has seen 7K RPM a few times. I use the cave man approach to wet sump, and only let it drain back overnight after a ride before shutting the door on the oil feed. I have mastered human nature and don't forget the valve is there though (anymore:oops:). Not recommended for people with multiple motorcycles in their garage, or younger guys still partying all night long and getting up early the next day to race or ride. It would be real easy to forget the valve is there, and end up with yet another Norton rebuild project.
 
Fast Eddie said:
Ok kids, yesterday I performed a very scientific test.

Actually, by accident…

I’m not sure when I last ran the Commando, but it definitely hasn’t run this year, so it’s probably close to a year since it ran.

I did a lot of things to it, stripped and rebuilt the forks, new battery with different wiring arrangement, new front tyre, etc, etc. But I knew that all oils etc had been refreshed prior, so oil wasn’t on my mind.

The Commando is the only bike in my shed that wet sumps…

So… I forgot all about the wet sumping didn’t I !

When it was finished, I pressed the button on the cNw starter motor, it took a couple of goes, then ROAR… it ran well and when a bit warm, ticked over nicely.

It was only after I’d switched it of that I suddenly thought F**K … the SUMP… !!!

Long story short… the NYC sump plug breather handled an entire sump full of oil without any issue. No kicking over to empty the sump, just press and ROAR !!

I wouldn’t do this deliberately by the way, but nevertheless it was a conclusive test !
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Perhaps there's a case to mod the lube system to one bigger pressure pump and let the breather valve do all the scavenging? Speedway motors use crankcase pressure to circulate the lubrication. They're low pressure systems much the same as the return on our Nortons. :)
 
Sp
cash said:
Perhaps there's a case to mod the lube system to one bigger pressure pump and let the breather valve do all the scavenging? Speedway motors use crankcase pressure to circulate the lubrication. They're low pressure systems much the same as the return on our Nortons. :)
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Speedway motors are an interesting example. The old 2 valve Jawa/Eso 500s used a one way valve at the bottom of the case and just blew the used oil down onto the track. I'm not sure if any of the speedway motors use reed valves but the Honda 450 single uses a sump reed valve to help keep oil off the crankshaft. Some of the BMW boxers also upgraded from a one way check valve to a reed valve.
 
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jseng1 said:
Sp

Speedway motors are an interesting example. The old 2 valve Jawa/Eso 500s used a one way valve at the bottom of the case and just blew the used oil down onto the track. I'm not sure if any of the speedway motors use reed valves but the Honda 450 single uses a sump reed valve to help keep oil off the crankshaft. Some of the BMW boxers also upgraded from a one way check valve to a reed valve.
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Total loss motors are a bad thing these days. GM four valve laydown motors have a reed valve in the top of the wet sump that uses crankcase pressure to pump the oil around the engine. I believe the JAWA has a similar system, though I haven't had one of these apart. The GM motor is such a simple design it's brilliant.
 
cash said:
Total loss motors are a bad thing these days. GM four valve laydown motors have a reed valve in the top of the wet sump that uses crankcase pressure to pump the oil around the engine. I believe the JAWA has a similar system, though I haven't had one of these apart. The GM motor is such a simple design it's brilliant.
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Been thinking, to replace the return pump a small valved in bleed might be required to ensure continual flow.
 
Schwany said:
That is funny.

It is a PITA even without the oil in there. Almost as much fun as changing gearbox sprockets.

How can you tell it is not the oil return returning the oil? Can you see the breather exit inside the oil tank? I have no idea what is inside an Commando oil tank.
Click to expand...
Oil is inside a commando oil tank....sometimes.
 
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