'70 camshaft breather not working - tach drive leaking? (2014)

NickZ said:

Mine is a '71 with the center stand mounted to the engine cradle, so I think that means I could use the Jim Comstock sump breather.

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If that's the case, you should do that. People who posted after your first post mentioned the timed breather port, so I assumed you had the whole early model system with the cross member that blocks the Jim Comstock breather. In my case, I have this breather



and this breather below both in operation.




To Slick, Yes I agree, the tiny holes in the cam maybe a limiter on the camshaft port capacity even if the disc is removed. Since I couldn't make Jim Comstock completely redesign his sump breather to suit my needs... (*yeah, kidding) I had to make due with the two reed breather's that would work. And yes, I did mount the Jim Schmidt breather so I knew I was getting a better seal on the timed camshaft breather port, and yes that stopped whatever miniscule crankcase leakage that would occasionally appear.

Sorry if I misled you Nick, I assumed you couldn't use the comstock breather, which I would have used if I could.

o0norton0o said:

If that's the case, you should do that. People who posted after your first post mentioned the timed breather port, so I assumed you had the whole early model system with the cross member that blocks the Jim Comstock breather. In my case, I have this breather

and this breather below both in operation.

To Slick, Yes I agree, the tiny holes in the cam maybe a limiter on the camshaft port capacity even if the disc is removed. Since I couldn't make Jim Comstock completely redesign his sump breather to suit my needs... (*yeah, kidding) I had to make due with the two reed breather's that would work. And yes, I did mount the Jim Schmidt breather so I knew I was getting a better seal on the timed camshaft breather port, and yes that stopped whatever miniscule crankcase leakage that would occasionally appear.

Sorry if I misled you Nick, I assumed you couldn't use the comstock breather, which I would have used if I could.

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No worries! Thanks for explaining your set up. Looks good.

I'm still a little unclear on the Comstock breather. The unit I see on the CNW website seems to be for installing on the breather port that exists on the back of the drive side case on '72 & some '73 750 engines. My '71 does not have this. I saw references on another thread ("CNW '72 Breather Mod", November 2014) to a Comstock breather that seems to go on the large sump plug, which I do have. Is that also a "comstock' breather? And where can I get that one?

o0norton0o said:

If that's the case, you should do that. People who posted after your first post mentioned the timed breather port, so I assumed you had the whole early model system with the cross member that blocks the Jim Comstock breather. In my case, I have this breather

and this breather below both in operation.

To Slick, Yes I agree, the tiny holes in the cam maybe a limiter on the camshaft port capacity even if the disc is removed. Since I couldn't make Jim Comstock completely redesign his sump breather to suit my needs... (*yeah, kidding) I had to make due with the two reed breather's that would work. And yes, I did mount the Jim Schmidt breather so I knew I was getting a better seal on the timed camshaft breather port, and yes that stopped whatever miniscule crankcase leakage that would occasionally appear.

Sorry if I misled you Nick, I assumed you couldn't use the comstock breather, which I would have used if I could.

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The best setup for you would be to remove the rotating disc and spring (whenever your cases happen to be split), Then plug the vents to the timing chest and remove the magneto plate breather. That way you won't pump air in and out of your timing chest and the case side breather will be more effective. But if its working for now I would leave it until the cases have to be split.

NickZ said:

Has anyone tried putting an in line reed valve in a tube venting from the intake rocker cover? I think I read somewhere that this been used as a potential solution.

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The method you reference is known. Norton officially tried it on the "anna" famous NORTON 650 manxman intake cover breather.
Norton also quit using it quite quickly. It seems to me as counter productive to draining the head drain oil past the lifters with an even larger uphill blow of crankcase air. I have seen it installed on fairly a recent build by named businesses. They have lost my respect.

dynodave said:

The method you reference is known. Norton officially tried it on the "anna" famous NORTON 650 manxman intake cover breather.
Norton also quit using it quite quickly. It seems to me as counter productive to draining the head drain oil past the lifters with an even larger uphill blow of crankcase air. I have seen it installed on fairly a recent build by named businesses. They have lost my respect.

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I persuaded a mate to fit a breather valve many years ago and he shortly after fitted a small breather into one of the inlet rocker covers to get the crankcase air flow to assist the oil flow down onto the cam. With diaphragm breather valves we are recommended to drill a small bypass hole the the valve body, perhaps we should use my mate Trevor's idea instead ?
Dave

I wouldn't fit a reed valve on a valve cover, and I think Slicks right that the timed cam breather port has the added restriction of having to enter the hollow camshaft through the small holes in the camshaft reducing it's potential efficiency, but it's still better than a "valve cover mounted breather" IMO.

Nick, If you don't have a crossmember in your frame close to your sump drain bolt, you can use Jim Comstock's sump plug breather. It replaces the sump's big drain bolt and cures a number of norton ills with one well designed part. I'm sure if you send Jim (Comnoz) a message, he'll tell you where you can get one...

cash said:

into one of the inlet rocker covers

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rocker shaft?

Hydraulic oiler gallery? high or puke pressure type? How do you expect this to function?
or is this a delayed april 1st joke!

o0norton0o said:

If that's the case, you should do that. People who posted after your first post mentioned the timed breather port, so I assumed you had the whole early model system with the cross member that blocks the Jim Comstock breather. In my case, I have this breather

and this breather below both in operation.

To Slick, Yes I agree, the tiny holes in the cam maybe a limiter on the camshaft port capacity even if the disc is removed. Since I couldn't make Jim Comstock completely redesign his sump breather to suit my needs... (*yeah, kidding) I had to make due with the two reed breather's that would work. And yes, I did mount the Jim Schmidt breather so I knew I was getting a better seal on the timed camshaft breather port, and yes that stopped whatever miniscule crankcase leakage that would occasionally appear.

Sorry if I misled you Nick, I assumed you couldn't use the comstock breather, which I would have used if I could.

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Does this setup work well on your bike?
I have similar with the reed on the timing cover and still with the original timed breather from the cam tee'd together and into the oil tank
Cheers

I could write a whole manifesto on the evolution of my bike.

Originally, with just the timed breather port, my bike leaked oil occasionally from whichever joint or gasket felt like taking a piss... I was young and norton guru's back then told me that I didn't know how to put together a leak free bike, and I believed them to some degree. Once I started to hear that the leaking was based on the parallel twin's crankcase pressure force, I started following the next path which was the reed valve.

I first did the blanking plate modification. I actually drilled an extra hole between the timing chest and crankcase to help get air out of the crankcase and into the timing chest more effectively. Leakage stopped mostly, but there was always a little bit here and there.

People said to plug the timed breather port, and I said, "NO, because 2 exit points for air moves more air than 1 exit point". Of course they can't refute that, yet they will keep saying to plug the second port. It's one of the things that makes discussing stuff here difficult.

The only question in my mind was whether the original breather sealed well enough to prevent air leaking backwards on the upstroke,...

SO,... Having my bike set up with the timed disc and the blanking plate breather working together, I occasionally got some weepage from the usual spots. (tachometer cable for one) Then I added Jim Schmidt's reed breather and I don't get weepage at the tach cable joint anymore, and I never did the improved "O-ring" modification to the tachometer base.

My conclusion was that the addition of the second reed valve improved the seal on the crankcase while still allowing it to breath through the double breathers, so if leakage is a sign of lower crankcase pressure, then I would conclude that the additional reed valve helped lower my crankcase pressure and also occasional leakage. It could not have added any extra capacity since I did not remove the timed disc breather. That is my conclusion

The double reed valve works good enough for me... Anyone else do the same modification?...

I am thinking of drilling out the discs,... while they are in place,... with some unique techinques that would scare the hair off your bulldog

MichaelB said:

https://nycnorton.com/product/reed-valve-breather-kit/

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Thanks. Exactly what I was asking about.

NickZ said:

Thanks. Exactly what I was asking about.

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I’ve run one of those for 6 years now. Works perfectly. Zero machining work to fit it. Maintenance free. Difficult to think of any downside at all really.

o0norton0o said:

I could write a whole manifesto on the evolution of my bike.

Originally, with just the timed breather port, my bike leaked oil occasionally from whichever joint or gasket felt like taking a piss... I was young and norton guru's back then told me that I didn't know how to put together a leak free bike, and I believed them to some degree. Once I started to hear that the leaking was based on the parallel twin's crankcase pressure force, I started following the next path which was the reed valve.

I first did the blanking plate modification. I actually drilled an extra hole between the timing chest and crankcase to help get air out of the crankcase and into the timing chest more effectively. Leakage stopped mostly, but there was always a little bit here and there.

People said to plug the timed breather port, and I said, "NO, because 2 exit points for air moves more air than 1 exit point". Of course they can't refute that, yet they will keep saying to plug the second port. It's one of the things that makes discussing stuff here difficult.

The only question in my mind was whether the original breather sealed well enough to prevent air leaking backwards on the upstroke,...

SO,... Having my bike set up with the timed disc and the blanking plate breather working together, I occasionally got some weepage from the usual spots. (tachometer cable for one) Then I added Jim Schmidt's reed breather and I don't get weepage at the tach cable joint anymore, and I never did the improved "O-ring" modification the the cable base.

My conclusion was that the addition of the second reed valve improved the seal on the crankcase while still allowing it to breath through the double breathers, so if leakage is a sign of lower crankcase pressure, then I would conclude that the additional reed valve helped lower my crankcase pressure. It could not have added any extra capacity since I did not remove the timed disc breather. That is my conclusion

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Your conclusions make sense to me. I think I will proceed with adding the Comstock sump breather sold by NYCNorton, and leave the timed disc breather in place and see if that solves my tach leak problem.

And besides, Kenny is a class act which on does not mind giving their money to.

Wow, I bought one of those comstock valves to put on my 70, and of course the brace between the frame prevented that. I think it was the first Jim knew of it. It was about $125 back then, (what year ?) but he gave me a refund. I got it directly from him then. Too bad I couldn't use it. But the only leaks I get are actually from the crank case joint where I did a poor job of sealing it with Hylomar. I'm still using the original timed breather system, but with a catch bottle.

dynodave said:

rocker shaft?

Hydraulic oiler gallery? high or puke pressure type? How do you expect this to function?
or is this a delayed april 1st joke!

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Sorry! the rocker cover. The hose was a only about 4mm ID and he just ran it up under the petrol tank. His idea was the negative crankcase pressure caused by the breather valve would draw air through the small bore hose into the rocker box and down into the crankcase assisting oil return.
Dave

Once the reed valve breather is in place the positive pressure air is removed and not allowed to re-enter. This means that there is a slight vacuum in the crankcase when the pistons are rising. Once the positive pressure air is pumped out, very little air is moving in and out of the cases. This means that the hollow cam has plenty of ventilation, but you want to remove the rotary disc and spring first chance you get.

You can tell its working by making this test. Loosen the oil cap and let it sit on the oil tank. Before adding the reed valve breather the oil cap will bounce up and down at idle. After adding the reed breather the oil cap will just sit on the oil tank and not bounce.

1 ea intake valve cover
2 ea exhaust valve cover

cash said:

His idea was the negative crankcase pressure caused by the breather valve would draw air through the small bore hose into the rocker box and down into the crankcase assisting oil return.

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Unfortunately the positive and negative pressure cycles under the pistons would likely never change except for ring blow-by which raises the bottom end crank case pressure. The normal (flawed) thought is to vent it out the top through the intake valve cover and unfortunately inhibits a more orderly oil downward exit from the lifter tunnel and the intake timing chest vent.
In actuality it mus be more like a huff and puff hurricane, but the attempted blow-by upward flow can not possibly help oil flow downward.

Now that you explain to better understand your friends effort, it would however only raise the crank case pressure and increase the bottom end pressure and the oil leaks.

dynodave said:

1 ea intake valve cover
2 ea exhaust valve cover



Unfortunately the positive and negative pressure cycles under the pistons would likely never change except for ring blow-by which raises the bottom end crank case pressure. The normal (flawed) thought is to vent it out the top through the intake valve cover and inhibits a more orderly oil downward exit from the lifter tunnel and the intake timing chest vent.
In actuality it mus be more like a huff and puff hurricane, but the attempted blow-by upward flow can not possibly help oil flow downward.

Now that you explain to better understand your friends effort, it would however only raise the crank case pressure and increase the bottom end pressure and the oil leaks.

Click to expand...

I agree that is why I never did it, however his bike ran just fine no ill effects at all?
Dave

NickZ said:

No worries! Thanks for explaining your set up. Looks good.

I'm still a little unclear on the Comstock breather. The unit I see on the CNW website seems to be for installing on the breather port that exists on the back of the drive side case on '72 & some '73 750 engines. My '71 does not have this. I saw references on another thread ("CNW '72 Breather Mod", November 2014) to a Comstock breather that seems to go on the large sump plug, which I do have. Is that also a "comstock' breather? And where can I get that one?

Click to expand...

That is the original design. You can get it from me or CNW. Jim