Engine breather disc

The set of cases I am putting in my bike does not appear to have the ability to mount the breather disc, did a search ( one of DogtT's posts ) on this and apparently the disc was discontinued from 72 or there abouts...

Is there any problem with running an engine without a breather disc on the end of the cam (DS) ?. Breather routed to oil tank......will post photos.

Mick Hemmings in his DVD, I think, just blocks off the LS timed breather and puts in a new breather system with extra holes in the timing side crank case. So, no, that timed breather should not be needed if you have another.

Dave
69S

Hi DogT.

Am intending on using the breather, just without the disc, thoughts ?, the engine previously had a line attached to the blanking plate over the "magneto" hole.

Or would using the higher placed " magneto" blank hole be a better choice and just blank off the front LH breather hole ?.

So, no, that timed breather should not be needed if you have another.

Click to expand...

Another "breather" or "timed breather" ?.

Everything I have read indicates the 'timed breather' was not too effective, but there are people using it and not complaining. If I wanted to do it correctly, I would blank off the timed breather, with or without the disk, and install a new breathing system from the 'magneto' area or in the lower back of the crank like CNW does, but that also involves drilling holes from the timing side into the crank case. I am not the expert, so do your own exploration of this issue, please. There are plenty of threads on this issue, and they are quite confusing, at least to me.

Dave
69S

This is what was on the installed engine:

Looks like you have some sort of a breather there, but is it a one way valve or what? That area on my '69 is part of the casting, so I would have to make a hole there. Believe me, I am not the expert here. You really need to look into the options, and they go all the way from timed breather valves out of the magneto area to expensive modifications from CNW.

Better seals always help, but negative air pressure in the crank keeps oil in, instead of trying to push it out.

Dave
69S

Josh Cox said:

The set of cases I am putting in my bike does not appear to have the ability to mount the breather disc, did a search ( one of DogtT's posts ) on this and apparently the disc was discontinued from 72 or there abouts...

Is there any problem with running an engine without a breather disc on the end of the cam (DS) ?. Breather routed to oil tank......will post photos.

Click to expand...

My personal bike is a '71 with the timed breather...

The timed breather on the end of the cam is OK...better than the breather setup on the '72 in my opinion. For your '71 I would either get the timed disc that goes on the end of the cam and scrap that ugly deal on the mag cover OR what I suggest is sending the cases off to CNW for the breather upgrade.

I've used the CNW mod on a number of engines for clients and plan on pulling my own this winter for that sole purpose.

If you reassemble without the disc, all the engine is going to be doing is pushing out on the down stroke and sucking in on the up.

Seriously, do youself a big favor and send the cases to CNW for the mod and have them do the clean up treatment on the cases.

After reading your posting again, it sounds like you might not fully understand the timed disc. The disc goes on the end of the cam shaft, inside the case. The stock cam has two notches where two tabs on the disc line up, the disc has two holes 180d from each other. So, by the operation of the cam, when the pistons are on their way down (pressurizing the case) the two hole on the disc line up with holes in the case allowing the air inside the case to be expelled. When the pistons are on their way up in the bores, the holes do no line up, therefore not allowing air to be sucked back in. This will be obvious when you split the cases...if the disc is still on the end of the cam.

You can actually see the timed breather working if you take off the angle fitting and look in the hole. You should see the 2 fan shaped openings and under that the timed breather valve. If you turn the crank over you will see the inner valve rotate, opening and closing the vent, if it is all in there correctly.

Dave
69S

On all mine I've left the breather disc out and installed and in-line KrankVent. I've also installed a second breather line, the pic is of a 66 atlas but would work the same on a commando.

Thanks Builder, I understand how the breather works etc etc, the previous owner has stripped the breather mount and then re-welded it, it is not possible to mount the disc as the facing is not flat nor is the locating pin hole usable.

The other cases have that magneto hole set up for the breather ( with no one way flow restriction ) "and" the timed disc, the timed disc would be completely ineffective due to the other breather.