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

NickZ said:

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.

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If you install my reed breather then you need to plug the existing breather. Cam or otherwise.
Leaving both connected kills the resonance that the reed needs to operate efficiently. Jim

cash said:

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

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In reality my second commando, a combat was my first build done in 1987, it did not leak at all until around 2002. Then the oil pump blew up in around 2003-4 because the oil pump ate a broken intake valve spring.

I would often joke and get on the ground next to the bike and look around. Guys would ask whatcha lookin for?... sez I "I'm looking for the leak" Guy sez "fimd it?

"SEZ I" Nope it doesn't leak.......

I posted this on a different thread and realize it belonged here. To follow up on my recent experience with th on my 71, which was leaking quite a bit at the tach housing / cable junction. I first tried to solve it by replacing the standard timed breather with the beautiful (and not cheap) sump reed valve unit supplied by NYC Norton. That change had no noticeable effect on the leak. I then pulled the housing in order to add the oil seal per the INOA tech digest and several threads on this forum. Surprisingly, I found that the shaft on my tach drive gear has no groove for an 'O' ring and, of course, no 'O' ring either. That probably explains why it was leaking. To do the oil seal mod, I used the Honda seal, 91207-222-000, which is listed as 7mm x 14mm. The OD of this seal is actually 14.5mm (which is also what is printed on the side of the seal) so the 0.51" drilling of the housing specified in the INOA tech digest is nowhere near large enough to allow the seal to be fitted. I increased it to 9/16" and even that was very tight and not easy to get in. For good measure, I also stuck an 'O' ring at the top of the housing where the cable sheath screws down, as I believe others have described doing on this forum. Final result - no more leak. Clean & dry after 50 miles of use.

o0norton0o said:

....
In my own case, I have 2 reed breathers. and after I added Jim Schmidts timing port breather, ALL leaks stopped. I believe it's because the timing disc breather leaked air into the crankcase which reduced my vacuum. Because I had 2 reed breathers, I didn't have a restriction on exhausting air on the downstroke like a single breather in series with a reed breather would have. So the only possible improvement that helped my bike become leak free is that the timing port reed breather sealed better than the rotating disc...

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I have been waiting for someone to test the installation of a reed valve in the camshaft left case vent without removing the original rotating valve. By coincidence I got a call from someone yesterday who did just that. After his first test ride he told me that his leaks had stopped. I prefer removing the rotating valve and plugging the timing chest vents for increased efficiency. But its good to know that it works either way.



o0norton0o - I suggest you pinch off the hose at the timing side on your 2nd reed valve and see what happens.

jseng1 said:

I have been waiting for someone to test the installation of a reed valve in the camshaft left case vent without removing the original rotating valve. By coincidence I got a call from someone yesterday who did just that. After his first test ride he told me that his leaks had stopped. I prefer removing the rotating valve and plugging the timing chest vents for increased efficiency. But its good to know that it works either way.

o0norton0o - I suggest you pinch off the hose at the timing side on your 2nd reed valve and see what happens.

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Jim, My bike doesn't leak, so there's only 2 possible results of pinching off my timing side reed breather which works in concert with your camshaft reed breather.

1) No change observed and no leaks develop and you can say your reed breather is sufficient even with the timing disk left in place.
OR
2) My bike starts to leak, and it proves that 2 breathers work better than 1 breather alone.

Sorry, I'm not pinching off my other reed breather, Jim. I have great respect for you and the great stuff you make, but I have no desire to do anything where the potential result is my bike is leaking again somewhere. I've had enough decades of having a leaky commando, to not want to go there ever again. As I have said before, the timing side reed breather got me to where I had almost never had leaks. I added your reed breather because the orginal stock timing disc breather doesn't seal as well as a reed valve seals. My bike is good now and isn't going backward to attempt to prove a point.

o0norton0o said:

Jim, My bike doesn't leak, so there's only 2 possible results of pinching off my timing side reed breather which works in concert with your camshaft reed breather.

1) No change observed and no leaks develop and you can say your reed breather is sufficient even with the timing disk left in place.
OR
2) My bike starts to leak, and it proves that 2 breathers work better than 1 breather alone.

Sorry, I'm not pinching off my other reed breather, Jim. I have great respect for you and the great stuff you make, but I have no desire to do anything where the potential result is my bike is leaking again somewhere. I've had enough decades of having a leaky commando, to not want to go there ever again. As I have said before, the timing side reed breather got me to where I had almost never had leaks. I added your reed breather because the orginal stock timing disc breather doesn't seal as well as a reed valve seals. My bike is good now and isn't going backward to attempt to prove a point.

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Its your bike and you will do what you think is best. I was just suggesting a temporary test. Both reed breathers work the same. Its a question of location.