Modified crankcase oil seal set up.

Jed · Nov 5, 2012

The normal set up for the oil seal on the drive side of the crankcase is a circlip holding the oil seal in place
After pulling out what was left of my hair (and thankfully before destroying a perfectly good big end bearing) I found no circlip and two oil seals instead
Although a leak is evident it seems to have done the job but does anyone know if this is a common practice?
Maybe there would be no leak if the circlip was in place?

When the sludge traps are cleaned out I'm on the way back

Cheers

Jed

JimC · Nov 5, 2012

There is no circlip on the drive side oil seal. It's a friction fit.

Many clumsy attempts to keep the crankshaft oil seal from leaking have been tried. Eventually, you'll find that it's crankcase pressure that's causing the leak, not a faulty seal. I've changed those seals until I was dizzy, only to see the leak continue. Once I installed a reed type crankcase valve I had no more leaks.

Jed · Nov 5, 2012

Thanks for the tip Jim
I"ll look into the reed valve fix

L.A.B. · Nov 5, 2012

Jed said:
Although a leak is evident it seems to have done the job but does anyone know if this is a common practice?
Maybe there would be no leak if the circlip was in place?

Never heard of it before. I can't see how a second seal could work, as it would be running on the reduced diameter section of the shaft and virtually on the engine sprocket taper. :?

Oil can leak around the outside of the seal so I recommend you use some sealant when you fit the seal in the housing, also apply sealant to the four stud threads.

JimC · Nov 5, 2012

Oil can leak around the outside of the seal so I recommend you use some sealant when you fit the seal in the housing, also apply sealant to the four stud threads

The above is good advice, as well. I would add that the sealing is in addition to, not in lieu of, installing a reed type PCV valve.

Torontonian · Nov 5, 2012

He's talking Mk 111. Uses a ciclip to retain. Contact MikesXS.com for reed valve. Also Hair Club for Men.

L.A.B. · Nov 5, 2012

Torontonian said:
He's talking Mk 111. Uses a ciclip to retain.

We knew (Edit: OK, I knew as I also own a Mk3) it is a Mk3 which has a circlip retainer-the sealant might stop oil seeping around the outside of the seal.

JimC · Nov 5, 2012

Torontonian said:
He's talking Mk 111. Uses a ciclip to retain. Contact MikesXS.com for reed valve. Also Hair Club for Men.

I stand corrected. There is indeed a circlip used for the seal on the MK III. I assumed it was a pre MKIII. I did notice the four holes in the crankcase for mounting the inner primary cover, but for some reason it just didn't connect. Like they say about assumptions.......

Did Norton recognize a problem with the oil seal blowing completely out of the boss? And the answer was to install a circlip? If so, that's really sad.

Jed · Nov 5, 2012

Sorry i forgot to add that it was a MK 111 and it has the breather on the timing side of the case
Wether that is sufficient to reduce internal pressure or not I don't know
The two seals made me think there was something in there that was put in before the bearing and the only way to get to it was by removing the bearing

I thought about the sealant and will probably try that with the circlip.
I don't understand why retaining the seal with a circlip is sad. What was done prior?

Jed

JimC · Nov 5, 2012

What I was referring to by sad was the fact that Norton engineers used a circlip to keep the seal in place rather than address the crankcase pressure problem, if that was the case. I don't know why the circlip was added for the MKIII. I'm only speculating.

There is a whole boatload of previous posts on breather valves. A search will bring up more than you will probably care to read. Basically, it's all about keeping the breather line closed on piston upstroke.

Jed · Nov 6, 2012

Thanks Jim

I did scan the breather tube posts but could not find much relating to the "missing" circlip nor the double oil seal idea.
As you say there are a lot of posts to get through trying to find an answer to what seems to be a peculiar application. Hence the dumb question
I see why someone might try two oil seals and while there was plenty of room to accommodate the two seals I wonder why a clip was necessary to begin with when a thicker oil seal would be as or maybe more successful in doing the job

I have found a thicker oil seal at a bearing shop but its not quite as thick as two genuine ones together so I guess its put it back the way its meant to be with sealant

Jed

Norton Dave · Nov 6, 2012

Hi Jed ,
just a word of warning bearing companys are good for some seals , but not usually high speed . Most only go to a couple of hundred RPM , I would go to a hydraulic seal company for maybe a viton double lip high pressure and high rotational seal . Thats my two bobs worth .

Jed · Nov 7, 2012

Thanks Dave but I will probably err on the side of caution and use genuine parts and look at the breather solution
Thanks again for the sprag

Jed

Modified crankcase oil seal set up.

Jed

JimC

Jed

L.A.B.

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