Oil-Bath Primary Chain Case

And RTV for chain case sealing

…else you won’t get it off again without distorting. Do it in the warm. It’s better for the rubber to mould to the shape and cures the RTV quicker. I bolt it up like that to cure into the correct shape.  Once cured remove the outer cover and smear with heavy grease.  Back on with the cover, wipe clean and leave it a while to skin over.

Jon

Before using a setting silicone ( which I found wanting) try running for a while with a  spray grease (not wax)  on the chain. And watch for oil leaks from other sources  . Sort these out first otherwise you will be dissapointed with the silicone  and struggle to get it off to see whats happening. I am using red rubber grease on the seal and find it helpfull.

I'm currently experimenting with a modern rubber 'D' seal on my 1954 ES2.  I discussed this with a rubber extrusions company in Bristol and they gave me two samples of D section rubber seals and some flat rubber to make the joint.  They were happy to supply short lengths to me and I think it works out at about £30 per chaincase.  I simply cut the ends very carefully square then superglued the ends together.

The beauty of the D section is that the flat face can be fixed onto the inner chaincase, then with the D section slightly wider than the gap, it compresses as the outer chaincase is pushed on and adjusts to any distortion of the outer case.

So far it seems to work very well, but I need to do some decent miles on the ES2 before I can claim it's the best thing since sliced bread!

The original set up by the manual works fine. Make sure everything is as it should be, clean and not distorted. I use the original rubber seal (fitted the correct way round - it makes a difference!) and some grease. I use SAE 10-30 tractor oil for the chaincase. Spray on grease does not work. One ride from Edinburgh to Bristol trying that reduced a new primary chain to scrap. 

At present I am using this stuff

https://www.sealantsandtoolsdirect.co.uk/everbuild-sealant-polyethylene-backer-rod-10m-x-20mm-back19

Unfortunately it is grey, not black.  But it seems to be the first time it's working on a machine with a particularly determined leak.

Some owners seem to be luckier than others in keeping them oiltight.  Every time I have solved it, I have been disappointed not long afterwards.

Its well worth taking lots of time to make the case work.. On a bike used for normal  classic  riding the chain is pretty much everlasting .  Even when I used to commute accross London  and thrash the bike  in the evenings  racing other " oiks ",  with Sunday runs to the coast   ,70 miles in 60 mins   I  dont remember  replacing the primary chain.. Current bike and chain been in regular use for 25 years plus.

I am using 90W gearbox oil in my 1959 ES2 primary chaincase.  It seems to work well and doesn't affect the clutch [I also use it in my Mk.III Commando]. Probably because it is thicker it seems to leak less. I welcome all the suggestions but would draw a line at Philip Ham's line about using sliced bread...

I like the idea of plasticine.  My Inter has 1932 engine and frame, so that's before they fitted the oil bath.  The restorer in 1990 fitted an inner and outer but they are a slight compromise and the space for the band is uneven around the rear where it is closest to the frame.  Hence my use of the "backing rod" because it takes up variations.

My (late) friend had an ES2 which never leaked. Then he took the cover off, and it never sealed properly again.

I've had varying success with red rubber grease.  It helps on one bike, but on the other it sets like glue.  Not as strong a bond as silicone, but difficult to remove.

Interesting stuff regarding the seals. I had an ES2 and had no bother with the chaincase however the bike has been replaced by a 16H I am restoring and I cannot even get the outer cover to fit over the seal far enough to get the large nut on.  The seal is a standard one from the spares scheme. I had thought of reducing the width down from 1" to about 3/4". Anyone any ideas?

Many owners, with leaking Norton primary cases, tend to forget that there are two other potential pathways for the oil to make a bid for freedom.  

These being the footpeg and gearbox mainshaft holes in the inner cases. Purchasing a complete gasket kit in the 1960s provided a whole bundle of rubber, paper and cork items for sealing these gaps correctly and minimising any possible leaks. See attachment example.  A key fact to add in, at this point, being that if the engine crankshaft drive side seal is worn out then this will allow hot gases to flow straight into the primary case, pressurise it and then blow hot oil vapour through any gaps. Many owners fitting belt-drive conversion will testify to this problem.

Lines of goo around the rubber sealing band does help but on that part of the primary cases.

NOT   gear oil,    Whats recomended  is thin  non synthetic oil  or ATF  which  can be helpfull as its red .   I used green  EP 80 gear oil in the box, ATF in the chaincase and 40 monograde in the engine , this helped to identify the leaks  as  the oils look and smell different . Mostly the leaks turned out to be engine oil ( soon brown/black ).  I think Farm suppliers sell a usefull  20 grade. . 

The straight cut gears don't need EP oils. Although they no longer damage yellow metal bushes etc.  The Manuals recommend single grade engine oil. Temperature doesn't change as much as an engine, so multigrades will be at the wrong viscosity. Probably.  And gearboxes tend to destroy the viscosity improvers in old multigrades.  Hence BL cars used to smoke prematurely as their oil molecules got chopped up by their gears, and quickly became 20 grade.

The only green oil I know of now is Halford's 20/50.

EP 80  is normally greenish and does not change colour in the box ,so its usefull to  pinpoint leaks.Also it smells very different.  Its about the same viscosity as the recommended oil for the box.. As David says its not necessary for  any extra protection with our simple gears ,but  we are using it for another reason.Simple boxes in cars used engine oil then  EP 90  and later changed to ATF to reduce power losses . I suspect our box bushes would last longer if we run on ATF , has anyone tried it?.