Breather question

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sole survivor

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I can't seem to find an engine breather on my engine. There has to be one with that much internal pressure. I have two on my high compression small block Chrysler. Is it located somewhere off the oil tank? Like that tube that dumps into the stock air filter assembly? Doesn't seem very efficient. I have removed the stock air box as I have JS flatslides and K&N pod filters. After a long ride, especially with several hammer down accelerations I'll find a little bit of oil at the base of the rear cylinder heads. And the bike doesn't leak after I ride. Do you guys have any suggestions or backyard solutions?
 
If it is the bike in your avitar then we can only assume that it is out the left side of your crankcase at the camshaft.
Do you have a manual?
Who does the work on your bike?

When asking a question it is best not to leave to much to assumption.
 
Three typical places. Off the end of the cam, drive side. Off the back of the crankcase between the motor and the gearbox. Off the back of the timing chest at blanked off mag mount.


Russ
 
Like Pete said, if it's an early bike the breather is off the drive side, the pipe just below the cylinders and the tube goes back to the oil tank to return sump oil to the oil tank. The tube from the oil tank to the air box is just the oil tank breather, so it doesn't get pressurized either and supposedly burns oil vapor in the engine. If it does come off the drive side, it's on the end of the cam and it's a tiny hole in the center of the cam with a timed cam port that lets pressure out as the pistons go down and is blocked as the pistons go up, but it can't keep up under speed. See #46 here http://www.oldbritts.com/1971_g1.html That's the timed breather cap.

Dave
69S
 
pete.v said:
If it is the bike in your avitar then we can only assume that it is out the left side of your crankcase at the camshaft.
Do you have a manual?
Who does the work on your bike?

When asking a question it is best not to leave to much to assumption.
Click to expand...

My apologies. It is a 1970 Fastback. I do all the work on all my motorcycles. By shop manual doesn't mention a breather apparatus.
 
DogT said:
Like Pete said, if it's an early bike the breather is off the drive side, the pipe just below the cylinders and the tube goes back to the oil tank to return sump oil to the oil tank. The tube from the oil tank to the air box is just the oil tank breather, so it doesn't get pressurized either and supposedly burns oil vapor in the engine. If it does come off the drive side, it's on the end of the cam and it's a tiny hole in the center of the cam with a timed cam port that lets pressure out as the pistons go down and is blocked as the pistons go up, but it can't keep up under speed. See #46 here http://www.oldbritts.com/1971_g1.html That's the timed breather cap.

Dave
69S
Click to expand...

It this something I could identify without removing covers from either side? The motorcycle is unrestored so I'd expect to see something that represents a min size K&N air filter. Like I have on my Triumphs. Cam cover on the right side(shift side) houses the Trispark. Let side is the primary with the alternator.
So I am assuming its on the left side.

Maybe I should stop riding it every weekend and work on it. I just thought there was a modification someone has done with success as the bike run great.
But oil under pressure has to go someplace.
Still learning. But I love this bike.
Thanks for the diagram.
 
All the way forward on the left side, near the top of the crankcase is a rounded knob, On the early bikes it was drilled and tapped for an elbow to thread in, that is the breather port. It is entirely possible somebody removed and plugged it. In which case I would think the bike would be much happier with a breather installed.

Here is an eBay auction for a 750 case. In the very first photo, upper-left. You can see the rounded knob with a machined flat and a tapped hole in the center.

http://www.ebay.com/itm/Norton-Commando ... 7e&vxp=mtr

Russ
 
Two other places for breathers, back of the timing case, where the Magneto would have been or some one might have fitted a Comnoz sump plug breather. I have fitted it to my 71, I will find out how it works in a few weeks time. Take a look at the breather threads on this site.

Just check all the oil lines coming from the oil tank, one should be part of the crankcase breather system
 
Found it. It is connected. Since it is a 1970 the breather line goes from the back of the engine block to the oil tank. It seems to be the same diameter as the two oil feed lines that head down towards the engine. About 1 inch in diameter. And the oil tank breather is still connected. It terminates on the rear of the air filter mounting plate. But..and there is always a but..there is another 1/4 inch line that feeds from one of the oil feed(or return) linescoming from the oil tank. Its about a foot long and just hangs down between the engine and transmission. Between the engine cradle. I've always know its been there. All diagrams(well all the diagrams I can find which are the 850cc engine size) I have seen show that it is there, even my shop manual, but none of them show that it is connected to anything. Or what its for. Mine has screw in it. I presume to prevent oil from flowing out. What purpose would that line serve? Does anyone have the oiling system diagram for a 1971 and earlier without an oil filter? Thanks for all the help. My motorcycle would never have been rideable without you guys answering my questions.
 
chasbmw said:
Two other places for breathers, back of the timing case, where the Magneto would have been or some one might have fitted a Comnoz sump plug breather. I have fitted it to my 71, I will find out how it works in a few weeks time. Take a look at the breather threads on this site.

Just check all the oil lines coming from the oil tank, one should be part of the crankcase breather system
Click to expand...

You'll like the Comnoz breather. Made a lot of difference on mine as far as emptying mildly wet sumped crankcases and curing oil seeps/weeps.
 
sole survivor said:
Found it. It is connected. Since it is a 1970 the breather line goes from the back of the engine block to the oil tank. It seems to be the same diameter as the two oil feed lines that head down towards the engine. About 1 inch in diameter. And the oil tank breather is still connected. It terminates on the rear of the air filter mounting plate. But..and there is always a but..there is another 1/4 inch line that feeds from one of the oil feed(or return) linescoming from the oil tank. Its about a foot long and just hangs down between the engine and transmission. Between the engine cradle. I've always know its been there. All diagrams(well all the diagrams I can find which are the 850cc engine size) I have seen show that it is there, even my shop manual, but none of them show that it is connected to anything. Or what its for. Mine has screw in it. I presume to prevent oil from flowing out. What purpose would that line serve? Does anyone have the oiling system diagram for a 1971 and earlier without an oil filter? Thanks for all the help. My motorcycle would never have been rideable without you guys answering my questions.
Click to expand...

Chain oiler ??
 
MikeG said:
sole survivor said:
Found it. It is connected. Since it is a 1970 the breather line goes from the back of the engine block to the oil tank. It seems to be the same diameter as the two oil feed lines that head down towards the engine. About 1 inch in diameter. And the oil tank breather is still connected. It terminates on the rear of the air filter mounting plate. But..and there is always a but..there is another 1/4 inch line that feeds from one of the oil feed(or return) linescoming from the oil tank. Its about a foot long and just hangs down between the engine and transmission. Between the engine cradle. I've always know its been there. All diagrams(well all the diagrams I can find which are the 850cc engine size) I have seen show that it is there, even my shop manual, but none of them show that it is connected to anything. Or what its for. Mine has screw in it. I presume to prevent oil from flowing out. What purpose would that line serve? Does anyone have the oiling system diagram for a 1971 and earlier without an oil filter? Thanks for all the help. My motorcycle would never have been rideable without you guys answering my questions.
Click to expand...

Chain oiler ??
Click to expand...
Yup, that's it.
 
chasbmw said:
MikeG said:
sole survivor said:
Found it. It is connected. Since it is a 1970 the breather line goes from the back of the engine block to the oil tank. It seems to be the same diameter as the two oil feed lines that head down towards the engine. About 1 inch in diameter. And the oil tank breather is still connected. It terminates on the rear of the air filter mounting plate. But..and there is always a but..there is another 1/4 inch line that feeds from one of the oil feed(or return) linescoming from the oil tank. Its about a foot long and just hangs down between the engine and transmission. Between the engine cradle. I've always know its been there. All diagrams(well all the diagrams I can find which are the 850cc engine size) I have seen show that it is there, even my shop manual, but none of them show that it is connected to anything. Or what its for. Mine has screw in it. I presume to prevent oil from flowing out. What purpose would that line serve? Does anyone have the oiling system diagram for a 1971 and earlier without an oil filter? Thanks for all the help. My motorcycle would never have been rideable without you guys answering my questions.
Click to expand...

Chain oiler ??
Click to expand...
Yup, that's it.
Click to expand...

I thought that too. But when I removed the screw oil was pumping out of it with the engine running. More than any chain would require.
 
That thinner pipe is the chain oiler and it should go to a small nozzle fitted to your chain guard. The early chain guard should be a curved item rather than the later straight one. The nozzle has a 1/4 inch bore steel tube across it to mount inside the chain guard with a 1/4 " bolt. Ta Da
 
gripper said:
That thinner pipe is the chain oiler and it should go to a small nozzle fitted to your chain guard. The early chain guard should be a curved item rather than the later straight one. The nozzle has a 1/4 inch bore steel tube across it to mount inside the chain guard with a 1/4 " bolt. Ta Da
Click to expand...

I'll check that. Pretty sure that is missing though it is, to the best of my knowledge, the original chain guard for a Fastback. And I am still bamboozled on how you would adjust the flow of oil to the chain. It must be missing. But, I too, use chain lube. Less mess. And I am not so much of a restorer of motorcycles but rather keeping them mechanically safe and reliable while letting a patina take over.
 
Your engine number begins with 135 and it has the breather off the back of the case? How long have you had this bike? Did somebody else freshly rebuild it? I am just asking because the breather you describe did not go into production until 1972 unless somebody has machined the case. Did you look for the knob as described on the left forward side? Does it have a plug in it?

Here is the blow-up of the '71 crankcase. Part number 41 is the breather elbow.

http://www.oldbritts.com/1971_g4.html

Here is the blow-up of the '72. Part number 46 is the breather housing.

http://www.oldbritts.com/1972_g4.html

Russ
 
135524 will be the FB MKII. So no cigar exhausts and peashooters instead. So with that engine number there should be a right angle fitting off the drive side with a rubber hose on it that goes to the oil tank for the engine breather.

Breather question


If not, it's been modified, which is not unusual. It's been usual to replace that fitting with a bolt and put a one way valve on the old magneto hole, but it should still go to the oil tank, but some just dump it to the ground.

I think you need to tell us for sure where all your hoses go, it sounds like it's been changed. There is also the chain oiler, which should come off the oil tank banjo and be a small line through a felt gasket that drips on the chain, that may also have been modified.

I'm running mine with the original breather situation, less the chain oiler, and it works for me, but I have an S model which has a different oil tank than yours.

A good breather on your engine can make it run better and leak less, but it needs to be set up right.

Dave
69S
 
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