The "Oil Bath" Primary

It has been done,  there will be a thousand posts on the subject. Avoid  hard setting masticks  as they can be almost impossible to remove.

I usually use a bit of silicon around the bottom half of the outer case, if you put it all the way around it can be difficult to remove without splitting the sealing band, which generally works.

If you want authenticity, my great-uncle who had Nortons in the '30s, incuding BLV 689, a 1938 M18 which he bought new, told me that he used melted tallow, available in great amounts in the Birkenhead shipyards, pour it in and lean the bike against a wall until it had set,but again, don't overdo it!

Even the most well set up cases tend to leak a drip or so during or just after use. Mine goes for months without topping up, Its possible that a little oil passes the crank seal and keeps it topped up. Carefull assembly  ,a true case, check no part of the outer case fouls anything, A band without slack, A good smear of Red Rubber silicon grease , and you may join the select band of "little drips". Oh yes,  I did form a  half circle of setting bath silicon on the inner case behind the clutch to direct the oil away from the box shaft area.

Read the manual carefully when fitting the rubber band. Get it the wrong way round and you will have an insoluble leak. 

I've not had occasion to refit a primary chaincase for many a year now, but I believe that all the bands I bought back then had an irregular section, that is to say a slight but perceptible taper across their width. So you had a "thick" and a "thin" edge- it was this thin edge that should face up against the inner chaincase, and the "thick" edge went against the inside of the outer case.

Hoe that makes sense- but I dont know if bands available today have this same taper, or like many things have been flattened in the name of cheapness.

Mike

There seem to be at least two band types. Rectangular with a lip on the outer edge and a wedge shaped one I saw on a featherbed ES2.  I've not seen clear descriptions in any of my books. I'm using red rubber grease to try to reduce leaks at present. 

Looking back at my earlier post and thinking about it, yes of course the "thick" edge has to butt up against the inner chaincase. This makes the taper follow any corresponding taper on the outer chaincase: doing it my way would of course be a recipe for disaster in terms of sealing, as very little of the 2 faces would be in contact, and a significant air gap would remain- with consequent leakage.

In my defence, it was well past cocoa time last night when I posted......and I'm still ****ed off I was too late yesterday to buy an e- ticket for Kempton Park today, there being no tickets for sale at the gate this morning :-(

The oilbath on my Dommie still leaks despite replacing the band and using various sealants. I've heard that they can be distorted by over tightening. Would anyone know how to check for distortion and more important how to return to the original profile ??

Many thanks  Ian

HI Ian ,John Hudson did an article on how to straighten out a bent cover.  It will be on the site somewhere.   Steve,  Put the minimum amount of oil in the case ,just enough that the chain edge can pick up some as you kick it over,a torch helps to spot the result. Too much oil  tends to affect the clutch. I use  10/40 cheap stuff which is nice and thin .

Hi Robert, Thanks for the heads up on the John Hudson article. Here's a link should anyone else need it

https://www.nortonownersclub.org/html/archive/rh/183/29/index.html#zoom=z