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Does anybody know why on a 1970 commando oil tank elbow vent has a restricter in it. thats the one that is inside the air filter area.
1970 Commando oil tank vent restricter.
- Thread starter Peter Restaino
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I'm guessing, but is it because
a) you want to put a partial -ve pressure in the oil tank, but don't want too much?
b) there will be oil vapour in the air from the tank and don't want to saturate the filter with too much oil?
Do you have a picture of the restrictor so we can see what it looks like, I have a 1970 Commando but switched to a K&N filter with no vent about 45 years ago, and I can't remember much about the original filter case
a) you want to put a partial -ve pressure in the oil tank, but don't want too much?
b) there will be oil vapour in the air from the tank and don't want to saturate the filter with too much oil?
Do you have a picture of the restrictor so we can see what it looks like, I have a 1970 Commando but switched to a K&N filter with no vent about 45 years ago, and I can't remember much about the original filter case
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Not good with posting a photo but someone suggested it could limmit the amout of oil entering the air fillter and ill buy that.
marshg246
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There are two types of central oil tanks. One has the crankcase vent connection to the side of the froth tower and the other has it to the top of the tank. In both cases, the tube to the air filter starts inside, near the top of the froth tower.
If the breather connection is in the side of the froth tower, it points at the open end of the tube to the air cleaner and any oil in the breather blows right into the air cleaner tube. With the standard breather setup, this is OK but if you have an add-on reed valve a large amount of oil can be sent to the air filter. Most likely, someone was trying to resolve that. If the breather instead goes to the top of the tank, there is no issue and there should only be air going to the air filter with perhaps a tiny bit of oil mist.
You can read about my battle with this starting at November 18, 2022 here: https://gregmarsh.com/MC/Norton/Blue69S.aspx
If the breather connection is in the side of the froth tower, it points at the open end of the tube to the air cleaner and any oil in the breather blows right into the air cleaner tube. With the standard breather setup, this is OK but if you have an add-on reed valve a large amount of oil can be sent to the air filter. Most likely, someone was trying to resolve that. If the breather instead goes to the top of the tank, there is no issue and there should only be air going to the air filter with perhaps a tiny bit of oil mist.
You can read about my battle with this starting at November 18, 2022 here: https://gregmarsh.com/MC/Norton/Blue69S.aspx
ashman
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I run my crank breather into a catch bottle as well my oil tank breather, the 1ltr plastic bottle sit between my rear engine mounts behind the GB, the breather hoses go to the bottom of the bottle and the air is vented through the top of the bottle as well have an extra vent hole beside the top bottle top where the hoses enter the bottle, been using this set up since 1982 stops the oil tank getting too much pressure from the crank breather and any oil mist just sits on the bottom of the catch bottle after a few years running I only get a very small amount of oil in the catch bottle.
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I read and seen the pictures of Greg Marshes 69S and have concluded that I will do the JS reed valve at the cam port and remove the rotory vave and spring but not shure if I will drill out the restricter in the vent elbow. A catch can may used also thanks guys for your advises.
Ashman,
I don't understand how you can run your crankcase breather onto a plastic bottle. Mine is constantly spitting out oil and blowby and has to go into the oil tank to catch the oil and separate it from fumes. Oil tank fumes then go to a plastic bottle. If not, the oil tank would run dry
Dennis
I don't understand how you can run your crankcase breather onto a plastic bottle. Mine is constantly spitting out oil and blowby and has to go into the oil tank to catch the oil and separate it from fumes. Oil tank fumes then go to a plastic bottle. If not, the oil tank would run dry
Dennis
marshg246
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Catch bottle won't work - WAY too much oil if you have the reed valve breather into the side of the froth tower. If you have it into the top of the oil tank, then there's no need/place for a catch bottle - it's in a perfect location. There's nothing wrong with air going into the air cleaner.
I was going to add a connection to the top of the tank but then I found the right kind of tank on eBay.
marshg246
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Seems we're getting apples, oranges, peaches and parts mixed up here!
The original timed breathers at the drive side of the camshaft probably can vent anywhere - very little oil involved.
Adding a reed valve (cNw, NYC Norton, JS Motorsport) will return a lot of oil via the breather - that cannot be caught in a bottle.
The center oil tank has two versions. One with the breather connection on the top of the tank and one with it into the side of the tower on top of the tank. All breathers work great into the top of the tank and I can think of no reason to do otherwise. Only the original is compatible with the side of the tower.
Adding a connection to the top of the tank, if not there, means a tube with one end threaded, a hole in the top of the tank, two nuts, two sealing washers, and some manual dexterity.
BTW, I can't figure out the part numbers or years of the two types of center tanks but I certainly bought the one needed!
The original timed breathers at the drive side of the camshaft probably can vent anywhere - very little oil involved.
Adding a reed valve (cNw, NYC Norton, JS Motorsport) will return a lot of oil via the breather - that cannot be caught in a bottle.
The center oil tank has two versions. One with the breather connection on the top of the tank and one with it into the side of the tower on top of the tank. All breathers work great into the top of the tank and I can think of no reason to do otherwise. Only the original is compatible with the side of the tower.
Adding a connection to the top of the tank, if not there, means a tube with one end threaded, a hole in the top of the tank, two nuts, two sealing washers, and some manual dexterity.
BTW, I can't figure out the part numbers or years of the two types of center tanks but I certainly bought the one needed!
ashman
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I get very little oil mixed in with the breather fumes, I also run a XS650 reed valve where it comes out of the back of the timing case so only one way pressure, its been yrs since I have emptied the catch bottle and it only had a very small amount of oil in it, so I get very little oil in my blowby.
You can see the top of the catch bottle and the reed valve just hiding behind the oil line hose coming back from my Lochead oil cooler, the back of my motor was very dirty when I took these pics, I had an oil leak out of the bottom valve cover studs at the time, these pics were taken about 15+years ago, bit of sealant on the studs and new silicone gaskets from Jim fixed that oil seepage.
My Norton is no show pony and well ridden.
Ashley
marshg246
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That's just a PVC valve at the top rear of the timing chest - nothing like the reed valve breathers at the bottom of the crankcase. There should basically be no oil at the top rear of the timing chest - there's nothing there to lube - and a PCV valve installed other than as designed isn't doing much!
And, do you really have the Commando central oil tank and Commando early air cleaner like is being discussed here? IMHO, there's already enough confusion in this thread!
ashman
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A lot of people run the XS650 reed valve on their Commandos, one way breather, as for the catch bottle even on my old Commando the breather system going back to the oil tank caused the tank to get more pressure in it and I use to get seepage out of the oil tank filler cap, also don't get any blowby or oil mist in my air filter, I also found the oil turned black quicker with the breather running into the oil tank as well stops the oil from frothing up as bad, my oil tank never needs toping up between oil changes, so my oil tank never runs dry.
marshg246
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Since there's an open tube in the oil tank way above the oil level that connects to the air cleaner, I see no way for pressure to build up. You have no blow by because you are breathing from the top of the engine where there is no oil. The Yamaha XS650 PCV valve does have an actual reed unlike most old car PCVs, but it must be oriented correctly and it is supposed to have a safety hole drilled in it. When a breather does not breath, really bad things happen!
Regardless, that's not what the OP asked about and based upon feedback here he's planning to add things that may well make his problem worse!
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So a JS reed valve breather at the cam breather port and the oil tank with the breather hose going to the froth tower woudnt work? I thought it would be a problem only if the JS reed valve was at the bottom of the engine like Gregs 69. Thats where all the oil is especialy if wet sumped. PS I did an experiment with the oil tank. I sprayed a garden hose at the froth tower and water did come out of the vent elbow but I was blasting it. You dont think it will work the way I want to do it ?
marshg246
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Post a link to the JS breather you're talking about - I'm not aware of a JS breather to the cam port, and I can't imagine one with the timed breather still in place. If really just in inline with the current breather I can't see it changing anything in regard to your initial question.
I put a reed valve breather on every bike I build and they are always near the bottom of the engine. Besides improving breathing, they return excess oil very quickly, like when wet sump'ed and the always have oil in the air. For 1972/73, it's the cNw breather that screws onto the back of the engine where the breather was. For engines with the cases apart, they are sent to cNw to be machined for the breather. For the rest, JS or NYC.
I put a reed valve breather on every bike I build and they are always near the bottom of the engine. Besides improving breathing, they return excess oil very quickly, like when wet sump'ed and the always have oil in the air. For 1972/73, it's the cNw breather that screws onto the back of the engine where the breather was. For engines with the cases apart, they are sent to cNw to be machined for the breather. For the rest, JS or NYC.
marshg246
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Ya, but he keeps saying at the "cam port" which can only mean the inline version AFAIK. I wanted him to provide the link so I knew exactly what he meant.
