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Oil seal sizes

Submitted by richard_salt on Sun, 11/02/2024
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Nortons - General

Can anyone tell me the exact sizes for the two oil seals, gearbox drive side outer and engine crank shaft drive side? For my 57 Dominator.

I live in a place which uses the metric system, so will have to search well for these. Having the exact sizes will help a lot.

Would it be better to get metal case or rubber covered?

It has a bad oil leak from somewhere behind the primary case, and I'll fit new seals when I put it all together.

The existing seals are maybe 20 years old but the bike has done only 50 miles in this time.

Thank you.

Submitted by robert_tuck on Sun, 11/02/2024

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I am  thinking i would not  suspect the two mentioned seals without  a bit more investigation .i replaced those seals on my dommy 30 years ago and with lots of use they are still fine. How about removing the primary cover ,drain the oil ,replace the cover and go for a ride. If no leak then its not the seals , but the cover thats leaking. I would also pipe the breather to the rear of the machine to remove it from the investigation.

Submitted by richard_salt on Mon, 12/02/2024

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...I removed the outer cover, wiped it all down, rode it without the cover about 10 km, there was oil behind the inner case below the gearbox, dripping onto the floor.  No sign of the engine seal leaking, no sign of anything coming out of the engine breather (no pipe connected to the breather). The gearbox oil level is about 2 cm down. So it seems to be the gearbox seal. 

I thought that if I'm replacing one seal, I should do both.

Today I'm going to remove the inner case, take it for a ride, try to establish just what the problem is.

Thanks for your help.

Submitted by robert_tuck on Mon, 12/02/2024

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Sounds like it could be the Box , however the breather pipe is notorious for blowing its oil into the sprocket area . I used to use green oil in the box ,red in the chaincase and dirty brown (!) in the engine ,that helped identify the leak. If the box shaft has any up and down play the sleeve gear bushes need replacing and the play would wear out the seal.

Submitted by richard_salt on Wed, 14/02/2024

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... inner and outer chain cases removed (keeping my left foot well out!).

After about 8 miles, there was no leak at all from the engine seal.

Nothing obvious from behind the clutch, so it looks like the gearbox seal is ok.

The problem seems to be with the breather. Originally I had a short tube going to the engine sprocket. For my ride I put a long length of transparent tube on the breather running to high up on the bike, with a loop, giving me an oil trap. After the ride there was a slug of oil about 50mm long at the bottom of the loop.

There was no oil anywhere else. Now I need to fix the breather problem.

It seems to me that the best solution is a small tank under the seat with an inlet at the bottom, and an outlet at the top. This will allow the oil/air to separate with the oil running back to the engine when switched off. The outlet could be piped to the engine sprocket.

Thanks for the help.

 

Submitted by bob_matthews on Wed, 14/02/2024

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Hi Richard

I run my breather out to the back of the bike, along the mudguard and exiting behind the number plate. I also use a small inline pcv valve just behind the primary chaincase.  I do the same with the oil tank breather.

Submitted by robert_tuck on Thu, 15/02/2024

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Thats a shock ! , I got it right for once , but the issue would not have been resolved so speedily if you had not been prepared to  dive in and  work at it. I have been faffing about not making progress with my 650 , I need to get a grip and  put the effort in .   Good job Richard. .See you out there.

Submitted by richard_salt on Thu, 15/02/2024

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.Thank you Robert, It was your comment about the breather that set me off.

However, I am still puzzled about one thing. The engine blew oil not vapour into the pipe in the 6 mile ride. If I put a bottle in there, will it just fill up and then be pumped out of the top?

At which stage does vapour come out instead of oil? (BTW, I have an oil shut off valve so the engine did not have oil in it from wet-sumping; but I have no PCV valve)

Maybe it left the engine as vapour but condensed back to oil in the long length of plastic tube.

 

Submitted by robert_tuck on Thu, 15/02/2024

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The STD dommy breather has always been an issue . My 99 has perfect rings and bore and has the basic oil control rings and std Pump gears  .In other words its as good as Norton could make it.  I still was not happy with the relatively small amount of oil being ejected . I plumbed the breather into the oil tank and it works although some condensation will gather in the tank . I also enlarged the tank out breather ,but nothing comes out so rear chain gets some EP 90 brushed on. .Later bikes had the tank tower . Perhaps some better plumbing could get the oil to the tank and fumes out the breather . Do we have a fluids dynamics expert out there !. 

 


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