Dynamo cork gasket

Information relating to the Matchless G9 or AJS Model 20 500cc twin
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Dynamo cork gasket

Postby Oggers » Sat May 25, 2019 1:47 pm

Would you believe it! - post run this morning, nice oil streak below the dynamo (E3L) on the timing side. Off came the dynamo and it looks like the joint has gone twixt dynamo and timing case. Cork gasket (part 014141) looks flat, but I understand this is a difficult joint to seal properly.

Thoughts

Use O-ring instead and silicone.
Use new cork gasket and silicone.

Cork gasket alone does not seem thick enough and therefore not proud of the recess enough to form an oil tight joint on compression - thoughts welcome....

Many thanks again

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Re: Dynamo cork gasket

Postby Rob Harknett » Sat May 25, 2019 5:47 pm

I do not think the cork gasket is intended to keep oil in, as you only give a few drops every 4 / 5, 000 miles. So it seems you are putting too much in. The drive side bearing is just packed with grease, more or less for life.

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Re: Dynamo cork gasket

Postby ajscomboman » Sat May 25, 2019 7:02 pm

Its a twin Rob, the gasket is there to keep the oil in! Try using non synthetic felt (if you can find some, an old hat is sometimes useful) I've done that before with success.

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Re: Dynamo cork gasket

Postby Oggers » Sat May 25, 2019 7:07 pm

This is the cork ring gasket which allegedly seals the drive end of the dynamo and the timing case aperture. Oil needs to be kept in the timing case!

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Re: Dynamo cork gasket

Postby Rob Harknett » Sat May 25, 2019 10:49 pm

ajscomboman wrote:Its a twin Rob, the gasket is there to keep the oil in! Try using non synthetic felt (if you can find some, an old hat is sometimes useful) I've done that before with success.

Ah, I'm always thinking singles.

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Re: Dynamo cork gasket

Postby MalcW » Tue May 28, 2019 10:27 am

The cork gasket on my 650 twin seems to work OK. The trick is to make sure the dynamo is pressed firmly up against the back of the timing case when you do up the retaining strap and the draw bolt. I lean the bike against a suitable length of wood between the garage wall and the free end of the dynamo. very low tech, but it works.

Malc

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Re: Dynamo cork gasket

Postby Mick D » Tue May 28, 2019 10:51 am

Hi

I'd be tempted to go for a new gasket and seal it with either silicone or Blue Hylomar.

Regards Mick

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Re: Dynamo cork gasket

Postby Oggers » Wed May 29, 2019 7:53 am

Malc - Useful tip! Many thanks - I'll give it a go

Mick - Yes, exactly what I have planned.

I am somewhat concerned that I am not tackling the root cause, which could be a build up of pressure in the crankcase, thence to the timing cover and causing oil to leeach out of the timing case as previous and now fixed, and now the dynamo seal.

I have yet to check the breather valve on the crankshaft under the primary chaincase, but for sure that will be the next port of call if it leaks again.

Good bike when running though. It handles very well and is fairly responsive. Seems to be freeing up a little.....

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Re: Dynamo cork gasket

Postby g5wqian » Tue Jun 04, 2019 5:24 am

i used plenty of welseal on the cork gasket , i put the gasket on the dynamo first , welseal applied to any mating surfaces of gasket and then as malc says i used a way of pushing the dynamo up against the timing case with some wood and then tightened up the long bolt and strap bolt .
dont tighten the long bolt up too much though or it will strip the thread in the dynamo .

i left mine to set the welseal overnight before i ran engine .

prior to this i had an o-ring and silicone in there which someone else had fitted and it leaked , so i wouldnt use an o-ring , i favour the cork gasket .

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