Comstock / NYC sump breather test

Fast Eddie

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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 !
 

robs ss

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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 !
Would you be making this post if you had to replace the drive-side seal?:oops:;)
 

KiwiShane

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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 !
Thats reassuring...and in my humble opinion That breather is the very best money spent for your Commando ...they are brilliant
 

Onder

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I have one on my 850 Mk2. No doubt it relieves excess pressure. Don't have electric start so if you forget to drain you can hardly push the kicker down so less likely to blow out the seal. But it vomits
out the sump into the tank quite well.
 

YING

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I am in total agreement with Shane on this unit.Love the way it works and we are fortunate enough to have Jim to come up with this piece.Just my 2 cents
Mike
 

robs ss

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I'm not sure of comparison performance but Jim's rear/reed valve (as installed and sold by cNw) works a treat too.
More difficult to install, for sure, but I can't fault mine.
Cheers
Rob
 
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Fast Eddie

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I'm not sure of comparison performance but Jim's rear/reed valve (as installed and sold by cNw) works a treat too.
More difficult to install, for sure, but I can't fault mine.
Cheers
Rob

If there’s anything between them I suspect that the cNw ‘bolt to the back of the case’ version may perform even better. There’s not always room though, there wasn’t with my TTI box and Maney cases.
 
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The cNw reed breather also works on the back of the timing chest. Not what the cool kids would do with it, but it does work. I don't use it for wet sump worries. The cNw reed breather is used only for relieving crank case pressure on my motor.

Not remembering the bike was wet sumping for a year is a lot better than getting distracted by married life and not remembering to fill the oil tank after a filter change. How would I know that? :rolleyes:
 

Bonzo

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Apologies if I'm T-boning this thread, but it's sort of on topic :cool:

Which breather (sump or a timing case) would be preferable if one were to later install an Alton/CNW electric starter kit, with regard to space needed for the starter motor?
 

Fast Eddie

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Apologies if I'm T-boning this thread, but it's sort of on topic :cool:

Which breather (sump or a timing case) would be preferable if one were to later install an Alton/CNW electric starter kit, with regard to space needed for the starter motor?

Do you mean timing case, or crank case ?

The crank case mounted cNw breather can have the hose mounted up or down and still work fine, so I think you could use either.

But if fitting with the engine in situ, the sump plug type is obviously way easier.
 

robs ss

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Apologies if I'm T-boning this thread, but it's sort of on topic :cool:

Which breather (sump or a timing case) would be preferable if one were to later install an Alton/CNW electric starter kit, with regard to space needed for the starter motor?
I have the cNw electric start - does not come close to the reed on the back of the crankcase.
The std gearbox comes pretty close, but quite acceptable (hence @Fast Eddie 's comment about the TTI box)
There is still enough room to tension the 4 allen screws holding the reed case on - but I had to shorten a std allen key.

Of course the sump plug one doesn't have such issues.

If I had to make the choice again I would still go with the cNw version.
Cheers
 
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Apologies if I'm T-boning this thread, but it's sort of on topic :cool:

Which breather (sump or a timing case) would be preferable if one were to later install an Alton/CNW electric starter kit, with regard to space needed for the starter motor?
My cNw reed breather on the back of the timing chest example was out of necessity due to my exhaust being in the way of a sump type breather, which is by far the easiest to install if there is room for one.

Matt at cNw does not suggest putting the breather he sells on the back of the timing chest because it is not as efficient located there as it is on the back of the crank case.

Not all models of Norton will have crank cases machined for easy breather installation. If yours is not factory machined for a breather on the back of the crank case, the cases will need to be split to do the minor amount of machine work. It's a major job splitting the cases for a cNw breather.

I think the cNw breather works for me on the back of the timing chest, because I came up with my own 3-hole pattern through the timing side crank case based on what Norton did on models with a crank case breather near the back of the timing chest and made a unique shaped port for the breather.
 

SteveA

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I had planned to run up my race bike yesterday morning after sitting since September last year....actually I did....and with a Comstock breather fitted to the rear of the cases I wasn't planning to drain the sump and put the oil in the tank.....

But Wednesday afternoon I bottled it and drained 1.25 litres of oil out of the sump....the bike was on the bench anyway so no big effort.....maybe I would not have had a problem, but I am still pleased I did it!
 
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Go to your local parts supplier and get a 1/16 x 1-1/8 ID oring at PTO sprocket to prevent main seal blow out. Then you don't have to worry or drain the sump and there will be no "suddenly thought F**K … the SUMP… !!!"
 
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For some reason my barn yard engineering logic says a reed breather on the back of the cases won't return much in the way of oil to the oil tank via the vent hose. It might return some oily froth, but not a stream of pure oil. Only way oil is going to get back to the tank is via the oil return under oil pump pressure. The sump type breather might return some oil via the vent hose because it is closer to the bottom of the sump, but it won't empty the sump any lower than the top of that tube sticking up in the middle of the breather.

I let my Norton sit for 27 years. Both my sump and primary chain case were topped up with oil. I drained the sump, but it did not occur to me that I needed to drain the primary case. Then I topped off the oil tank. Once I got it started, I went around the block and when I returned, I noticed I had a 10 foot long x 3" wide stripe of oil in my driveway. I was wondering why that first left hander felt so loose at the rear end. ;)
 

Fast Eddie

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Go to your local parts supplier and get a 1/16 x 1-1/8 ID oring at PTO sprocket to prevent main seal blow out. Then you don't have to worry or drain the sump and there will be no "suddenly thought F**K … the SUMP… !!!"
I’m not really in the mood to strip my entire primary down just to install an o ring that might help prevent me from having to strip the entire primary down…!
 
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You
I’m not really in the mood to strip my entire primary down just to install and o ring that might help prevent me from having to strip the entire primary down…!
You don't have to do it now when everything is together. You do it when the primary is already stripped down or the engine is being rebuilt. From then on - no worries.
 
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Fast Eddie

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For some reason my barn yard engineering logic says a reed breather on the back of the cases won't return much in the way of oil to the oil tank via the vent hose. It might return some oily froth, but not a stream of pure oil. Only way oil is going to get back to the tank is via the oil return under oil pump pressure.

Well that’s not the case, the breather on the back of the case, or the sump plug type, returns EXCESS crankcase oil very quickly indeed.

Hardly surprising really as it has a 750cc or 850cc compressor pumping it !!
 
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I’m not really in the mood to strip my entire primary down just to install and o ring that might help prevent me from having to strip the entire primary down…!
That is funny.

It is a PITA even without the oil in there. Almost as much fun as changing gearbox sprockets.
Well that’s not the case, the breather on the back of the case, or the sump plug type, returns EXCESS crankcase oil very quickly indeed.

Hardly surprising really as it has a 750cc or 850cc compressor pumping it !!
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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