Crank case breather

Bruce, It sounds as though the breather on your oil tank could be blocked and so the pressure is venting through the chain oiler instead. The oil tank breather on the 750S with the central oil tank (I assume this is your model from your user name) vents from inside the tank to the outside through the air filter back plate. If you remove the air filter you will see a hole just above the two lower mounting bolts and this goes into the tank. I suggest that you try a bit of compressed air with the oil tank cap off and see if there is any getting through.

Dave M,

Do you know what is inside that round item the breather goes to on the 69-70? I assume it is some kind of separator, but on mine, there was always oil dripping out of that hole in the air filter and it made a mess because it would drip down on top of the gearbox. I know that there is a line from that round thing to the hole, and also a hole in the tube that probably is supposed to dump the separated breather oil back into the oil tank?? Fill me in please.

Dave
69S

Dave 69S, I've just had a look at a spare central oil tank that I have sitting on the bench, The inlet pipe on top of the raised extension on the tank - which I think is the round item you refer to - appears to terminate inside this extension and I expect it is simply an open ended pipe, the breather into the air filter is actually an internal tube that goes from the visible breather hole upwards, this also terminates inside the extension. The two pipes are not linked and you can blow through either while blocking up the other one and have an unimpeded flow. I will try to see whether I can get a small mirror in there for a more definitive answer.

I have to thank you, I have been working all day yesterday on my 750S (Chinese New Year holidays here) and your assistance and advice have been invaluable. I hope to have it fired up in a week or two.

Dave M,

Yes, I have experimented a bit with my oil tank since it is out. I can blow into either the top pipe where it goes into that round thing on top, or the bottom while blocking the other end and you can blow air through it. I think there is a pipe that goes from the top round thing to the front of the oil box where the air filter is, but there is a hole in that tube that is supposed to let oil out back into the tank. That's why I think it is supposed to be a vapor/oil separator. That is my thinking, but I always found that oil leaked out of the hole in the air filter hole. It would be interesting if anyone ever took apart that thing on top of the oil tank to see what was actually in there, I don't want to ruin mine though.

I'll bet that the tube that comes from the air filter area through the tank goes up into that round thing somewhere near the top, and the breather tube just dumps excess oil into that round thing and is supposed to dump the excess oil back into the tank, but some of it ends up going on into the air filter, and then on to the gearbox top.

Happy New Year in HK, I was there in 1959!!!!

Dave
69S

Re: Re:

69750S said:

The reed valve (Mike's XS valve) is up near the oil tank.
Thx for the fast reply. To answer the plumbing w/o removing the side cover I think the large port was toward the breather and the small outlet towards the tank. I had to cut a 45/70 brass cartridge for a ferrule to make the connection to the breather side hose as it was about 1/2 inch in diameter and the outlet side was about 7/16 but I managed to squeeze the 3/8 hose on it. Air would only blow from one direction (large to small outlet) so I positioned it so it would allow air out but not back in. I tried the Mity Mite but both valves I bought would allow air to flow freely in both directions.
Perhaps my connections are not airtight enuf. I had to use an adaptor I bought that was a 1/2 by 7/16 rubber elbow on the breather side and I couldn't get a hose clamp on one side as there wasn't much room, but I thought it was a tight fit.

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For breathers to work right, they must be placed as close to the crankcase as possible also, there should be no reduction in hose size.

Jean

DogT said:

Dave M,

Yes, I have experimented a bit with my oil tank since it is out. I can blow into either the top pipe where it goes into that round thing on top, or the bottom while blocking the other end and you can blow air through it. I think there is a pipe that goes from the top round thing to the front of the oil box where the air filter is, but there is a hole in that tube that is supposed to let oil out back into the tank. That's why I think it is supposed to be a vapor/oil separator. That is my thinking, but I always found that oil leaked out of the hole in the air filter hole. It would be interesting if anyone ever took apart that thing on top of the oil tank to see what was actually in there, I don't want to ruin mine though.

I'll bet that the tube that comes from the air filter area through the tank goes up into that round thing somewhere near the top, and the breather tube just dumps excess oil into that round thing and is supposed to dump the excess oil back into the tank, but some of it ends up going on into the air filter, and then on to the gearbox top.

Happy New Year in HK, I was there in 1959!!!!

Dave
69S

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What a great response; Thx all. I have some news (a revelation in fact) but I have to go to a Bday party so I can't post now. I'll take pix manana manana and post.
THX again to all.
Bruce






OK Here's what I found. I had two tubes going into the round receiver on top of the oil tank. The one on the right is the breather tube and I thought the other was a plugged steel inlet. However it was just a rubber plug that was forced into the hole (first photo) When I took that plug out I could see light in the tank when I put my flashlight into the oil cap hole. My "chain oiler" is in fact the connection you were referring to which comes out thru the back of the air filter backing plate into what would be the inside of the air filter. but since I'm running a K&N filter that outlet from the oil tank is exposed and that's what I had my chain oiler tube hooked to. No wonder I had so much oil spurting onto the chain that I wanted to block it up.
So I think what I will do is route that chain oiler tube back up into the hole on the top of the oil tank where the rubber plug was. There is no vapor separator like Dave talks about but at least the oil would go back into the tank instead of all over my rear wheel. What do you think?
Thx Jean for the tip on reducing the size of the line going into the reed valve, but I don't know how to remedy that since my breather hose is 3/8" coming out of the engine. I might just eliminate the reed valve entirely since Jim explained the principal of the disc breather inside the crankcase on these early Nortons.
Sorry for the size of the photos; I'm not sure how to reduce them altho I know it's been discussed somewhere on this forum. Hell this is the first time I've been able to have the pix show rather than some http language, but I remembered someone said to use the IMG format which I did. Next time I'll figure out how to reduce them. One step at a time. After all look at what I thought was the "chain oiler" That's why I love this forum; I ask stupid questions and you all are kind enuf not to point out my deficiencies. I have learned much here.
THX to all again.
Bruce
Oh the last photo is me with the Norton and my Scarmbler. A friend and I were out for a ride and he was riding my Scram.

Bruce, where are you? I get the feeling like AU? But it looks like SOCAL too.

I don't have that hole to the left in your pic. I only have the breather tube going into the tophat thingie. My chain oiler came off the smaller banjo that attaches to the return line, I soldered it shut. I've been inspecting it a bit tonight. The tube that goes into the air cleaner area, goes up into that round thingie, but not in the center, but towards the front of it. I need to get a small mirror and look up in there. I tried blowing in the hole from the air cleaner and it was pretty blocked, so I put some carb cleaner through it and pushed a nylon cable tie up in it to clean out the mud daubers crap that was in it. Now the carb cleaner has eaten off the paint and it is a mess (not an issue) but I need to do some more inspections on the tank. I also tried to blow in the small hole which is for the the return line banjo and it too seemed clogged so I did the carb cleaner and nylon tie thing through it too, but still there is a lot of back pressure trying to blow through it, but I know it comes out in that small hole which you can see inside where the filler cap goes on (so you know oil is flowing). When I spray carb cleaner in the breather input at the round thingie, I get it coming out inside the tank (the large hole at the bottom).

Nice looking "S", and the decals look good. Have you done much work on it?

If you keep your pics at 640 wide or smaller, they show up full size without extra effort on the site, I think photobucket lets you resize.

Dave
69S

I like the big pics. :mrgreen:

DogT said:

Bruce, where are you? I get the feeling like AU? But it looks like SOCAL too.

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No Juarez, Mexico just across the Rio Grande from El Paso, TX. That pic was taken at an old 2 mile road race course South of town that locals use for flying their radio control planes on the wkend. Some friends of mine were the owners but ran into some zoning restrictions or something that made them call the deal off, but it's a nice course on a moto providing you take care into a couple corners where the pavement has degraded into gravel.

DogT said:

I don't have that hole to the left in your pic. I only have the breather tube going into the tophat thingie. My chain oiler came off the smaller banjo that attaches to the return line, I soldered it shut.

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(Yes so does mine I discovered after poking around; it has a rubber hose and a bolt clamped in the end. I tried routing the air cleaner line thru the hole where I took the rubber nipple out, but it seems to generate a lot of froth in my oil so I went back to my setup with the air cleaner line routed to the rear of the bike and venting away from the tire. When I changed the line, I was going to take the reed valve off, but I got lazy and it was 66 deg out so I went for a ride. I was running fairly hard coming back about 90-95 and after slowly down coming into Juarez I noticed the bike started missing. So I just babied it home about 10 mi and when I got to my garage there was a huge gush of oil pooling under my bike. My reed valve setup had let go and the oil was flowing backwards out the breather hose. What a mess. My oil was down to where it was barely covering the strainer in the bottom of the tank. I guess when they don't have sufficient back pressure they miss. Don't know what else it could be since I changed the oil next day and it seems to run fine. I just checked the compression and I have 160 left and 170 right at 3,600 ft altitude. I didn't know about holding the throttle open tho when checking the comp. My comp gauge is an old one where you hold the rubber nozzle against the SP hole so it's difficult to hold and kick at the same time. Maybe I'll buy a new one, but the reason I cked is because I noticed that the right pipe seems to have a sharper push to the exhaust than the right and when I hold my palm against the top pipe opening it almost dies and when I hold it against the bottom pipe nothing happens. Not even a change in the idle. My left pipe tho is an original header. When I bought new headers from Baxter I couldn't get the flange nut over the bend on the left pipe so I just changed the right pipe which had some rust holes in it. The left has a few smaller holes and that's the only thing I can think accounts for this. Maybe enuf exhaust is escaping to account for this. That's why I checked the comp; thought I may have a problem.

DogT said:

I've been inspecting it a bit tonight. The tube that goes into the air cleaner area, goes up into that round thingie, but not in the center, but towards the front of it.

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(Yes that's where the hole on mine is- towards the front of where the breather hose goes in. There is nothing there just a hole- you can see directly into the tank thru that hole. Where is your oil water vapor separator? In the line coming from the air cleaner? Because it's not in the top hat.)

DogT said:

Nice looking "S", and the decals look good. Have you done much work on it?

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(No that's the way I found it, but the red color is boring for me. I like the sparkly blue like you have. I have an extra tank painted white with flames. I switch them back and forth, but I may redo it pearl white w/o flames.)
My bike had 10,350 mion the odo when I bought it. I ahve 11,400 on it now and most of that has been in the last two weeks since I fitted the Tri Spark ignition. I could never get a smooth idle before.

(Message edited by the moderator - L.A.B.)

69750S said:

Sorry for the size of the photos; I'm not sure how to reduce them altho I know it's been discussed somewhere on this forum.

Click to expand...

DogT said:

If you keep your pics at 640 wide or smaller, they show up full size without extra effort on the site, I think photobucket lets you resize.

Click to expand...

You can go up to about 900 image width before this site's auto cropper starts working.

So in Photobucket, select "more options" (below "Upload images & videos") then select the "800 x 600" or smaller upload resize option, or use the Photobucket photo edit "Resize" tool to reduce an uploaded image down to 900 wide or less, and then "Apply" and either "Save a copy" or "Replace original".


Alternatively, if you want people to see a full size image, for instance, to show fine detail more clearly, then add the original size photo's "Direct link" to your message instead of, or as well as, the "Img code".

Thanks for the picture info LAB.

Bruce,

69750S said:

Where is your oil water vapor separator? In the line coming from the air cleaner? Because it's not in the top hat.)

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I don't know that I have one. The way mine was setup when I got it and still is although all apart right now, is a pipe from the timed breather on the left of the crank to the round extension on top of the oil tank. The breather tube from the round extension just dumped into the old air filter setup and oil would drip down through the air filter onto the top of the gearbox. That was it. Like I said , I got tired of oil sloshing around out of that chain oiler, so I pinched it shut and soldered it closed and removed all that chain oiler crap. I am not sure what I am going to do when I get this all back together yet. Did you install a reed valve, if so where?

Looks like you are running without an oil filter?

Mine was originally the Fireflake Blue, but I got stupid one year and painted everything black, now I am trying to get it back, and am going with DupliColor Metal Specks Blue which for a rattle can is not too bad, but the flakes are not nearly as large as the old Fireflake. The blue color is right tho. I'm reticent about having it pro painted because of the expense and the f/g tank. Have you done anything about your tank? I'm thinking about using Avgas myself or I understand some marinas have non-ethanol gas.

I was in El Paso in '49 or '50 when my dad was working at White Sands. I started first grade there and I remember listening to the Les Paul and Mary Ford show every morning before school.

Dave
69S

I would really like the CNW mod for crankcase breathing but the reality is I'll probably never do it unless the engine needs to come apart for some other reason...like if I finally buy the Jim Schmidt pistons/rods!

The oem system ('73 850) had to feed into the intake to meet US (and maybe other countries') emission requirements. I plan to remove the breather hose from its connection to the oil tank, eliminate that restrictor fitting that drops the hose size from the one that fits on the crankcase breather tube to the size that fits on the tank, and run the breather hose from the breather tube to the rear of the bike so it is just an "open" air system. Seems logical that that would be more effective than the oem setup, especially since the ID of the hose to the tank and to the carb is much smaller than the actual crank breather hose.

I know that this "mod" has been done many times in the past but does anybody see any downside issue with doing it? I intend to run the hose completely to the rear of the bike, exiting at the top rear of the fender, between it and the underside of the fastback tailpiece.

MexicoMike said:

I would really like the CNW mod for crankcase breathing but the reality is I'll probably never do it unless the engine needs to come apart for some other reason...like if I finally buy the Jim Schmidt pistons/rods!

The oem system ('73 850) had to feed into the intake to meet US (and maybe other countries') emission requirements. I plan to remove the breather hose from its connection to the oil tank, eliminate that restrictor fitting that drops the hose size from the one that fits on the crankcase breather tube to the size that fits on the tank, and run the breather hose from the breather tube to the rear of the bike so it is just an "open" air system. Seems logical that that would be more effective than the oem setup, especially since the ID of the hose to the tank and to the carb is much smaller than the actual crank breather hose.

I know that this "mod" has been done many times in the past but does anybody see any downside issue with doing it? I intend to run the hose completely to the rear of the bike, exiting at the top rear of the fender, between it and the underside of the fastback tailpiece.

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I thought you were going to do the Mikes XS breather?

I intend to run the hose completely to the rear of the bike, exiting at the top rear of the fender, between it and the underside of the fastback tailpiece.

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Why? What's the purpose as opposed to venting to the tank? Seems to me you are going to have an oiled rear.

"
I thought you were going to do the Mikes XS breather"

Yes but I can't get the valve here so I figured in the interim, reducing the restriction to the flow caused by the entire plumbing to the tank setup would be useful. In any case, I plan to eliminate the tank plumbing anyway. As far as oiling the rear, that's possible if actual oil comes out of the breather but I could make a little separator out of a small plastic bottle that could sit in the battery area.

I believe that improving the ability of the air to flow in/out of the breather would also help the oil drainback from the intake rocker box by reducing the pressure in the timing case. Any pressure in the case is transferred to the passage from the rocker box; that pressure cannot help the draining, tending to want to push the oil back up into the box. I completely agree that the CNW mod, which essentially plugs the transfer holes from crankcase to timing case and takes the breathing vent to the crankcase is really a superior method in every way. But as I said, I would not disassemble the engine just to have that done.

MexicoMike said:

"
I thought you were going to do the Mikes XS breather"

Yes but I can't get the valve here so I figured in the interim, reducing the restriction to the flow caused by the entire plumbing to the tank setup would be useful. In any case, I plan to eliminate the tank plumbing anyway. As far as oiling the rear, that's possible if actual oil comes out of the breather but I could make a little separator out of a small plastic bottle that could sit in the battery area.

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You could have it delivered with the DVD. :mrgreen:

I might just be paranoid but I would worry about any system that didn't return oil to the tank. Of course on my bike the breather is on the back of the crankcase so it moves a lot of oil!

I thought of that but it turns out that we will be out of town during the time the visit will occur

Is the problem getting stuff through customs into Mexico, or is it a problem of getting retailers to mail it to you?

It's primarily the customs and sometimes retailers not wanting to ship to Mexico. A while back I ordered a $35 card reader from amazon. When it arrived here, customs wanted another $30 in charges. Sure, 60 bucks won't kill me but I just can't deal with that plus shipping is quite a bit more so now I buy all parts when I'm in the US and bring them back on the plane...you should have seen us carrying back all the new FG fastback parts - tank, side covers- tailpiece as well as the fender, two 19" rims and two 4.10 x 19 tires!