Crankcase breather pipe set-up

[55PAN]

I noticed in another thread that it was mentioned not to seal the breather tube. Well here's what my bike has. About ten years ago the previous owner put on a belt drive primary system and removed the pipe and sealed the breather hole and turned off the primary oiler. Then he drilled a hole in the oil tank dipstick and installed a nipple, put a hose on it and ran it towards the ground. When I got the bike it had been sitting for a year and there was a LOT of oil in the crankcase from sumping. When I kicked it you could here it sloshing around and when it started it all went back into the oil tank, none on the ground, it was about two quarts worth. I have since put over five hundred miles on it with no problems and it is pretty oil tight, no major leaks to speak of.
So I guess my question is... Is the motor breathing through the vent line to the oil tank and then through the hose on top of the dipstick? It's apparently been like this for ten years so it can't be that bad, could it? By the way the bike is a '55 FL.
Bruce

Hey guys, I know my post above was a little long but I still would like to know what you think of this set-up. In other posts people like "DuoDave" and "Plain" have said not to seal the breather tube but my set-up is a little different and I would like to know what you think about it. Thanks in advance for your opinions.

[PanPal]

I don't have an answer for you. I know how it is to write a thread and not get a reply. It sounds interesting and may work. It worked for 10 years. If I were running a belt, I'd look more into this, but I personally would probably route the pipe to the rear chain instead.

[Plain]

48Pan:

I think that the reason that you are not getting a lot of opinions is that this is a real butt scratcher. I have given it some thought and I do not have a "good" answer. I would not have done this. The breather huffs out a LOT of air. My opinion is that there is no really good gas relief on my oil tank, and the possibility exists that the tank and engine would pressurize. But, you are operating successfully with the set up, and it has been like that for a long time. The tip off would seem to be that the engine is not leaking oil in odd places, which it almost certainly would be if pressure was building up. You may well have taught this old dog a new trick. I don't run a belt on the primary because a chain gives me many more options for changing gears to get the ride I like. That and the fact that even in the face of advancing technology I remain a contrary old coot and think that a motorcycle should have a chain!
I remain skeptical that your engine is breathing correctly with this setup, but that certainly does not mean that it is not. It is taking me a while to get my head around this. It is a butt scratcher.

Adios-----Plain BSM

[55PAN]

PanPal and Plain; thanks for the reply. If the bike came with a chain primary I probably would have left it that way. This '55 is a birth year bike and I've been riding for over 33 years and I guess I kind of go for the old way of doing things, but I have to admit so far I really like this belt drive. For the time being I'll probably leave the venting this way since it doesn't seem to be causing a problem, but I would still like to hear anyboby elses opinion on this.

[DuoDave]

Many bikes have the engine breather venting into the oil tank. As you suggest, I suspect that when your breather opens, the crankcase pressure is escaping up the oil tank vent line into the oil tank. Since it seems to have worked okay so far, you may as well stick with it. Bet you have got the other guys running belt drives thinking now!

[Toymaster]

How big [ID] is the nipple and hose that 'vents' to the atmosphere?
I would think that the 'vent line' would be marginal to double as a breather, but it does seem to be working OK..
I would say that that 'vent' should at LEAST equal the 'vent line' in size..
And yes, an idea might be to aim that hose at the rear chain.. I would think there would be a 'mist' that would lube the chain [ but it COULD contain moisture also.. food for thought tho!]

[55PAN]

I checked the ID of the nipple and line that vents off the top of the dipstick and it is 1/4", which is about the same size as the nipple on the outside of the oil tank that the vent line from the motor is connected to. Also I think you have something there about a mist coming out of the hose. The hose is aimed at the frame brace that the seat post goes through and it always has an oil film on it. Maybe I will figure out a way to re-direct it to the rear chain.

By the way in case anybody is wondering, I changed my "name" to 55PAN from 48PAN since I sold the '48 and now have this '55FL.......Bruce

[madmikeharris]

Hey @55PAN I know this is a very old post, but I have a 60 and it has a belt drive and I have been looking for a solution as my start the other day looked like an Oil murder scene all over my garage as my vent puked all over my spinning belt... The belt is very well oiled to say the least, and so is a couple of other bikes and the garage floor and a cooler among other items, hahaha.
I guess I love this idea of the way you have it, so did you ever have any issues with the way it was set up or did you make any changes to it?

Thanks!
MM

[55PAN]

Hi MM, I sold the bike in 2016, but for the 12 years I owned it I left it as is. I never had any problems with it, so I just rode it as it had been set up.

[Andygears]

When I got my pan, from a long time friend, it had a similar setup. The primary vent line into a tee fitting on the crankcase breather line, and a hole tapped into the stock oil tank cap, with a line leading down to vent. But it had not been “trouble free”. Leaks! The thing sprang leaks everywhere over time, I assume because of pressure. From the time that bike was pieced together it always had an excess of oil pushing out the breather pipe in the primary.

When I totally rebuilt the engine, I changed a couple things. First, I pulled the pinion bushing from the cam cover, it had a “hot rod” bushing with a full circle groove to give full pressure all the time to the crank. That worked, the crank pin & rod bearings were like new despite many miles. But I believe there was too much oil into the crank, overloading the timed breather with opened case hole and no screen. 1949 right case, solid lifters, no hydraulic lifter oil passage. Second, it had a ‘65-‘69 oil pump which had broken keys on a few occasions, over 40 years, and had a small scar on the scavenge side of the pump casting. Maybe a weak return? There were other issues, cases out of line, mismatched deck surfaces, and left front motor mount egged out.

The rebuild included correct case studs, for alignment, milled deck surfaces & motormounts, aligned case bushings, correct 1950 oil pump, chain primary with breather pipe in place, new breather gear, oil tank sealed up cap. All works correctly now, I have adjusted the primary oil screw to give enough oil and all seems to breath correctly. I believe it is problematic to Route the breather “Upward” because the breather cannot generate enough pressure to force liquid up the hose. If it’s just vapor, it will work ok, but if you wet sump, crankcase pressure will build up and cause leaks.

A little long winded but might help somebody.

Andygears

[RooDog]

Andy....
I admire and understand your long term adventure with this motor. Sometimes trying to out-think, and re-engineer the MoCo does not turn out too well. But then, sometimes it does. You do understand hot rodding. Over a long period of time living with the same machine many changes will be attempted, some will remain, some will be undone, or redone differently. Many times we just get lucky !
My Panhead project was much like yours, and is still performing well, @ 74", since 1967. Many lessons learned and knowledge passed on here by the members. Keep the vintage knowledge flowing, both of the things that do work, and especially those that didn't....
Let's just keep 'em rolling.....
....RooDog....
PS: And always have a spare master link..... :

[Andygears]

For people who don’t know, I helped my friend, Dennis, build that engine in 1976 then moved away and bought it back in 2013. Many other hands were in it the intervening years. Dennis is a top shelf woodworker/carpenter, mechanic not so much. A loyal true friend.

Andygears