1962 Norton 650SS Crankcase breather / oil tank

Britstuff · Jan 8, 2021

Hi:

I have a few questions regarding the crankcase breather plumbing on my 1962 Norton 650SS.

The bike was purchased a few years ago. Nice and shiny on the outside, unfortunately much of the mechanicals proved to be extensively bodged, (apparently the guy who worked on it prior relied heavily on a hammer and chisel as his go to tools - and no, I am not exaggerating!). On the positive side it is a matching numbers, (home market) bike with its original 650 "18" "SS" motor. The engine has now been rebuilt, (including a set of rather impressive Jim schmidt trick lightweight pistons) and I / my mechanic are working on hooking everything back up prior to its first run.

When purchased, the crankcase breather, (located as I believe it should be, on the left rear of the crankcase) which has an approx 3/8" pipe aperture, was connected directly to an approx 1/4" pipe aperture on the top front of the oil tank. Oddly, to my mind at least, there is also a second 1/4" pipe aperture pointing down located towards the top of the rear of the oil tank, that has been blanked off. So it seems to me I would have a sort of a crankcase "suffocator"......

My questions are:

1. Is this the correct configuration?
2. Have I got the correct oil tank? I believe it is a Norton tank, but there seems to be quite a few different configurations / variants.
3. If I do have the correct oil tank, how is one supposed to manage the change in aperture diameter from approx 3/8" to 1/4"?

Thank you very much for your time and your patience with a Norton Newbie.

Kind Regards,

James

EstuaryBoy · Jan 8, 2021

To quote Roy Bacon:
'In general, both the 88ss and 650ss were both fitted with the standard 650 tank for 1962, but some had a modified tank with a froth tower at the top. With this arrangement, the engine breather was connected to the top of the tank and the lower was vented to feed any mist to the rear chain.'

texasSlick · Jan 8, 2021

The size difference is of little or no matter as to flow of gasses to the oil tank. You need to find, or conjure up, an adapter. One possibility is to fit a sleeve over the inlet tube to the oil tank, to bring the O.D. up to the 3/8" size.

I am not completely familiar with the pre-Atlas breather configurations, but my guess the blanked off tube is for venting the oil tank to either atmosphere, or, as in the Atlas, to the chain-guard to get some lubrication to the rear chain. In any event, you must vent the oil tank in some way.

Slick

Edit: I see EstuaryBoy beat me to the 'Enter' key. From your description, I do not think you have the froth tower. A picture of an oil tank having the froth tower is in this link:

Atlas/Dommie Oil Mist Scrubber

ATLAS/DOMMIE OIL MIST SCRUBBER I have owned my Atlas for over 50 years, and for most of that time I have been firmly convinced the "froth tower" was of little or no effectiveness in controlling oil mist escaping from the oil tank . Thus, having the tank off the machine for a new powder coat...

www.accessnorton.com

Matchless · Jan 8, 2021

I purchased my 10,000 mile old 1962 650 ss from the first owner so I know it's as it left the factory. As far as I remember, the breather from the inlet rocker cover goes to the oil tank & the pipe from the rear of the crank case goes to atmosphere. I will check this tomorrow when I'm back in the workshop & report back.

Martyn.

Britstuff · Jan 8, 2021

texasSlick said:
The size difference is of little or no matter as to flow of gasses to the oil tank. You need to find, or conjure up, an adapter. One possibility is to fit a sleeve over the inlet tube to the oil tank, to bring the O.D. up to the 3/8" size.

I am not completely familiar with the pre-Atlas breather configurations, but my guess the blanked off tube is for venting the oil tank to either atmosphere, or, as in the Atlas, to the chain-guard to get some lubrication to the rear chain. In any event, you must vent the oil tank in some way.

Slick

Edit: I see EstuaryBoy beat me to the 'Enter' key. From your description, I do not think you have the froth tower. A picture of an oil tank having the froth tower is in this link:

Atlas/Dommie Oil Mist Scrubber

ATLAS/DOMMIE OIL MIST SCRUBBER I have owned my Atlas for over 50 years, and for most of that time I have been firmly convinced the "froth tower" was of little or no effectiveness in controlling oil mist escaping from the oil tank . Thus, having the tank off the machine for a new powder coat...

www.accessnorton.com

Britstuff · Jan 8, 2021

Thank you all for your information. Very helpful indeed. Clearly I do not have an oil tank with a froth tower. I have been trying to work out how to post a URL to a photo of my tank so you can see what I have, hopefully this will work:

https://files.secureserver.net/public_file_binary.php?page_action=generate_image&hash=0sT7GkL0teNZVN&w=640&h=381

Bernhard · Jan 8, 2021

If it was my bike, I would have obtained an oil tank with a froth tower to upgrade it.

texasSlick · Jan 8, 2021

Bernhard said:
If it was my bike, I would have obtained an oil tank with a froth tower to upgrade it.

Early Dommies have a tool tray that will not allow the froth tower to fit. It may be possible to upgrading to an Atlas tool tray, and thus fit an oil tank with a froth tower.

Heck, anything is possible with enough kilobucks.

Slick

Matchless · Jan 11, 2021

Matchless said:
I purchased my 10,000 mile old 1962 650 ss from the first owner so I know it's as it left the factory. As far as I remember, the breather from the inlet rocker cover goes to the oil tank & the pipe from the rear of the crank case goes to atmosphere. I will check this tomorrow when I'm back in the workshop & report back.

Martyn.

Sorry for the delayed response. What I said above is correct. This is how it would have left Bracebridge Street. The later bikes didn't have the inlet rocker cover breather & the engine breather went to one of the tubes on the froth tower. This was a much better solution in my opinion, preventing the odd oily splodge on the driveway.

Britstuff · Jan 11, 2021

Hi Martyn:

Thank you!

Any chance of a picture or two? I can give you an email address if you like.

"Matchless"... I also have a 1959 AJS model 31 deluxe. Lovely bike that has kept me on two wheels while waiting to get the Norton back on the road.

Cheers,

James

dynodave · Jan 13, 2021

Britstuff said:
1. Is this the correct configuration?

A 61 manxman has only one tube that enters through the tank skin
yours seems to be a later slimline tank with two tubes.
The intake breather is actually a joke IMO
My 63 atlas has the tower/top hat with 2 tubes.

Britstuff · Jan 13, 2021

Thank you DynoDave, yours and the other replies have been incredibly helpful. At this point I think I will run the engine for the first time with the existing tank and see what happens, (breather attached to the front tube). It will be interesting to see how much oil (and or mist) comes out of the second tube. If tests are unsatisfactory, at least I now know what a tank with a froth tower looks like, so I can track one down if needed, (I think I have the later (narrower front on the oil tank side) tool tray that has room for a froth tower tank.

Cheers,

James

dynodave · Jan 14, 2021

Britstuff said:
Thank you DynoDave, yours and the other replies have been incredibly helpful. At this point I think I will run the engine for the first time with the existing tank and see what happens, (breather attached to the front tube). It will be interesting to see how much oil (and or mist) comes out of the second tube. If tests are unsatisfactory, at least I now know what a tank with a froth tower looks like, so I can track one down if needed, (I think I have the later (narrower front on the oil tank side) tool tray that has room for a froth tower tank.

Cheers,

James

You will discover the later tanks no longer have the attached shield for ? air cleaner, I believe I saw it on your pix. I would swap you for a later style tank.
dynodave small d
Northern New England Norton Owners NNENO

Britstuff · Jun 14, 2021

Hi Dynodave:

Thank you for your offer.

I wish I had looked at your post a week ago! Coincidently I recently purchased a later dominator oil tank with a froth tower. It has not arrived yet, but will hopefully arrive soon. I have been learning all about crankcase pressure with the dominator engine. On my bike, oil was leaking form pretty much everywhere on the timing cover side.

Looks like I had two problems. Firstly the standard timed breather was not working well at high rev's, (apparently not unusual), issue has now been hopefully resolved with the intstalation of an NYC Norton sump reed breather, (so far seems to work great). Second issue is my early oil tank does not breathe very well. When blowing on the front pipe the flow is clearly restricted, even though the oil tank rear pipe is now plumbed to be vented to atmosphere - not sure if this is how they were, or if mine has an issue? I am hoping the later tank will have a better flow.

Further to your statement regarding the plate with the ? air cleaner hole: yes, mine does have the hole. Are you saying that later dominators had no plate at all? Or was there a plate with no ? air cleaner hole?

Kind Regards,

James

Bernhard · Jun 14, 2021

Re oil tank pipes; one is bolted on(chrome) and should have a metal filter.
The other is the return pipe that goes up through an internal oil pipe with a little hole on the side near the top.

texasSlick · Jun 14, 2021

Britstuff said:
I recently purchased a later dominator oil tank with a froth tower. It has not arrived yet, but will hopefully arrive soon.

Kind Regards,

James

Be aware that Atlas/Dommie oil tanks have an inherent weakness at the point where the upper mounting flange (An "L" shaped tab at the top of the tank) is welded to the tank roof.
The tab flexes with vibration and fatigues the tank metal until failure, resulting in a leak that is easily mistaken for a filler cap leak.

PM me for a fix should you encounter this.

Slick

Britstuff · Jun 14, 2021

Hi Bernard:

Sorry if I was being a bit misleading. I am not refering to the main oil tank feed and return pipes, (on the bottom front of the oil tank). I am refering to the breather pipes, at the top of the tank. One on the front at the top, (feed) and one at the top rear of the tank, (to atmosphere) both pipes are only about 1/4" diameter aperture. Looks like the breather pipes on the later froth tower oil tanks are perhaps 3/8" diameter aperture, so hopefully it will breathe better.

I should explain that the NYC sump breather really needs to return to the oil tank. It throws out way more oil than the original crank case breather. Which of course makes sense, as it is much further down the engine. My oil tank with the 1/4" diameter aperture beather pipes, does not allow sufficient flow to keep the NYC sump breather happy.

Britstuff · Jun 14, 2021

Hi Slick:

Thank you for your advice. My new (to me) oil tank with froth tower, just arrived. Appears to be in very good order. The tab is attached with six spot welds, which I am assuming is how it left Plumstead. No sign of metal fatigue.

Cheers,

James

texasSlick · Mar 11, 2022

Britstuff said:
Hi Bernard:

Sorry if I was being a bit misleading. I am not refering to the main oil tank feed and return pipes, (on the bottom front of the oil tank). I am refering to the breather pipes, at the top of the tank. One on the front at the top, (feed) and one at the top rear of the tank, (to atmosphere) both pipes are only about 1/4" diameter aperture. Looks like the breather pipes on the later froth tower oil tanks are perhaps 3/8" diameter aperture, so hopefully it will breathe better.

I should explain that the NYC sump breather really needs to return to the oil tank. It throws out way more oil than the original crank case breather. Which of course makes sense, as it is much further down the engine. My oil tank with the 1/4" diameter aperture beather pipes, does not allow sufficient flow to keep the NYC sump breather happy.

Do not be concerned about the issue I have placed in bolt font above. There is an insignificant (about 2%) reduction in flow capacity for a reduced diameter section of a tube providing the length of the reduced section is short ... short is defined by less than 10 times the diameter of the reduced section. In this case, 10 x 0.25 is 2.5 inches which is about the length of the 1/4 inch section including the part inside the oil tank.

Slick

texasSlick · Mar 11, 2022

Britstuff said:
Hi Slick:

Thank you for your advice. My new (to me) oil tank with froth tower, just arrived. Appears to be in very good order. The tab is attached with six spot welds, which I am assuming is how it left Plumstead. No sign of metal fatigue.

Cheers,

James

The spot welds are the weak points. Eventually, (perhaps 30 to 50 K miles) vibration will fracture one or more welds, opening up a leak path from inside to outside the tank. The resulting leak, or weep is easily mistaken for a oil filler cap leak.
I first brazed the tab all around to stop the weep, but I do not recommend anyone to follow suit as this only contributed to the metal fatigue problem and precluded welding afterwards. The proper repair is to cut away the tank roof and replace the roof and tab with a heavier gauge steel.

Hopefully, you will have many miles of service before you have to address this issue.

Slick

BTW: Consider modifying your new froth tower oil tank with the following mod:

Atlas/Dommie Oil Mist Scrubber

ATLAS/DOMMIE OIL MIST SCRUBBER I have owned my Atlas for over 50 years, and for most of that time I have been firmly convinced the "froth tower" was of little or no effectiveness in controlling oil mist escaping from the oil tank . Thus, having the tank off the machine for a new powder coat...

www.accessnorton.com

This has worked out well for me.

1962 Norton 650SS Crankcase breather / oil tank

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