M31DL dynamo oil leak

[mjf65]

I've been living with a minor leak for a while but it's got progressively worse and now it has stopped charging, I fear the oil may have worked its way into the windings, is this possible? I've also been told there is a better solution to fixing this annoying fault by fitting an O ring rather than the cork gasket, is this also possible?

[Groily]

Sadly, oil can work its way across the dynamo cradle from the timing side, and into the commutator end, yes. It can also get in if the drive side oil seal is in a poor state or if the annular spacer it seats on on is scarred.
An O ring can certainly help with the joint.

The big hassle is the poor design here really. The draw stud reduces the land between the timing case and the dynamo, making the contact surface for a cork or other gasket very inadequate, and even an O ring is a squeeze. The depth of the register that enters the timing case is necessarily shallow. The stud can also pull the dynamo up 'not square' - ideally we need 2 fasteners, but there's no room and we wouldn't be able to get the dyn off without removing the timing cover).

Best advice seems to be to assemble, with goo, don't pull up the draw stud tight but compress the dynamo hard and squarely up against the cover by whatever means possible, leave to set overnight, and then do final (not aggressive) tightening of strap and stud.

Despite trying all the commonly-cited remedies, I still find that a genuinely oil tight seal usually lasts only a few thousand miles, then has to be looked at again. Oil mist is tolerable maybe, but when it develops into streaks which end up on your right boot . . . . it's sorely vexing!
A snug-fitting bearing retainer plate at the drive end is handy (some are a bit moth-eaten) but even with brand new ones this can still be a problem area. A thin gasket between the plate and the dynamo's main end plate can be useful, especially where there are any unused threaded holes in the latter.
I raise my hat off to those whose motors are 100% perfect in this regard and stay that way long term!

[mjf65]

Well I have finally removed the dynamo to discover that the cork gasket had split so no suprise that that oil had been steadily leaking out, plenty of hylomar used to help which has now been removed. As you have said Groily there is such a small gap between the stud for sealing and it looks really difficult to get the new cork washer in the gap. I have got an o ring kit and I recon that may well provide a better chance of of providing an oil tight seal.

[les ward]

I have found the new cork gaskets don't seal very well at all. When I used one from an old gasket set it cured the leak. The modern ones use a coarse type of cork and the old one a much finer cork and is also smaller.
I have reused this gasket several times and it still doesn't leak. When I experimented with a new gasket it leaked within 20 miles, so I put the old one back in and it didn't leak.
I now look for old, part used gasket sets on eBay/autojumbles for old/part used gasket sets.
A friend also had the same leak and we used one of the old gaskets I found and the old gasket cured his leak.
I also use a small round file to make a small indentation for the stud.

[farare]

I have found the new cork gaskets don't seal very well at all. When I used one from an old gasket set it cured the leak. The modern ones use a coarse type of cork and the old one a much finer cork and is also smaller.
I have reused this gasket several times and it still doesn't leak. When I experimented with a new gasket it leaked within 20 miles, so I put the old one back in and it didn't leak.Dinosaur Game
I now look for old, part used gasket sets on eBay/autojumbles for old/part used gasket sets.
A friend also had the same leak and we used one of the old gaskets I found and the old gasket cured his leak.
I also use a small round file to make a small indentation for the stud.

The oil leak not only raises questions about the immediate functionality of the dynamo but also poses a potential risk to other engine components. It is crucial to address this issue promptly to prevent any further damage and ensure the optimal performance of the dynamo.

[MalcW]

I've managed to get a decent seal on mine using a new cork gasket by filing a bit of a notch for the draw stud, covering it with Wellseal, then using a suitably sized sash clamp to press the dynamo fairly tightly into position before tightening the retaining strap.

Malc