Timing cover/dynamo leak 55 G9

Information relating to the Matchless G9 or AJS Model 20 500cc twin
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Re: Timing cover/dynamo leak 55 G9

Postby Mick D » Tue May 12, 2020 2:39 pm

Hi

If its anything like my E3L you should be able to find an order number, (part number), stamped into the body just below the 'Lucas'. This is the best indication of what you have and what it was originally intended for.

Regards Mick

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Re: Timing cover/dynamo leak 55 G9

Postby Oggers » Fri May 15, 2020 5:23 pm

Gents

Dyno drive end now in bits. Pulled off the pinion - easy enough with puller! Revealed the oil seal - Lucas part 188614 for a Dynamo 20035A. I'll also get hold of a shielded bearing, One more thing if I may. Armature shaft is 1/2 inch, seal has a bore of around 3/4, so there is a chamfered bush of hard plastic/nylon? which sits behind the seal and in front of the bearing and is a tight fit on the shaft. I cannot find that part anywhere!

So - I assume it is some sort of spacer/bush thing! The oil seal has no chance of sealing without it. So if i clean it up and replace it, with a new seal and bearing will I be OK?

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Re: Timing cover/dynamo leak 55 G9

Postby Groily » Fri May 15, 2020 8:57 pm

The collar is steel Oggers. On some dynamos - yours if original - it's a short tube basically, and a close (sometimes very close) fit on the shaft.

On many versions of the E3L it's actually a 'nut' screwing on to a threaded section on the shaft. If yours is per book though, the armature will be plain, and 178mm long: Lucas part #200712.
There are three basic versions of the E3L armature - parallel ended and keyed for a pinion, with plain shaft for the collar for our bikes, Nortons and Triumphs; very similar at 179mm but with the threaded 'nut' / collar for magdynamos (#200754); and threaded and taper-ended for dynamos driven by sprockets or pulleys on BSA pre-unit twins, 190mm long (#200752).

To see the idea, have a look at the Lucas instructions or E3Ls and E3LMs, where you'll see on page 3 of the pdf link here
http://www.brightsparkmagnetos.com/libr ... Pt%20A.pdf
a part designated 'R'. In that particular case it's threaded to go on to an E3LM, which is the magdynamo version of the dynamo, and has a different-shaped bearing retaining plate as you'll see. But the general idea is the same.

You'll note also a reference, in section (iv) of the associated text on that page, to an oil seal, part 'S' (illustrated with a dotted line in the exploded view because not all dynamos had need of one) but your one should, and it's the standard seal for any E3L. I don't know what the part number for the collar might be - but if your one is round, correct diameter still, and unscarred by pliers, vice jaws etc it will probably be OK. If it looks good, and the oil seal also looks good, then the problem probably isn't here to be honest, but it is well worth replacing the seal anyway, for the small cost of the thing.

A smear of wellseal or whatever between the bearing retainer and the dynamo end plate is a good thing. You mentioned that earlier I think. As also is a smear over the heads of the small countersunk screws that retain the plate (they have a habit of working loose in fact).

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Re: Timing cover/dynamo leak 55 G9

Postby Oggers » Fri May 15, 2020 9:27 pm

Groily

Not the collar. Definitely a plastic/nylon thing which is a close fit on the 1/2" shaft. OD of around 3/4", chamfered to about 45 degrees to mate with the oil seal rear face. The correct seal for the dyno has a bore of 3/4 inch so you definitely need it. No threaded nut, and this thing is not shown on the parts list either. Bearing and oil seal reasonably easy to come by, but cannot find this collar/bush/secondary seal anywhere.

As and aside, the silicone/rubber O-ring with a smear of silicone seemd to work. All oil free in that vicinity at least.

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Re: Timing cover/dynamo leak 55 G9

Postby Groily » Sat May 16, 2020 6:47 am

Hmm. Never come across a plasticky bit. Seems wrong to me and thus could be the prob. Even in steel they can wear a bit against the seal . . .

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Re: Timing cover/dynamo leak 55 G9

Postby ajscomboman » Sat May 16, 2020 11:02 am

Groily wrote:Hmm. Never come across a plasticky bit. Seems wrong to me and thus could be the prob. Even in steel they can wear a bit against the seal . . .


I'd have to agree with you there Bill, never ever seen any plastic tapered bit in any of the E3L's I stripped and rebuilt. Had plenty of the steel bushes wear grooves in though.

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Re: Timing cover/dynamo leak 55 G9

Postby Oggers » Sat May 16, 2020 4:18 pm

Chaps

Hopefully the attachments will speak a thousand words. The (main) oil seal - shown in the cover of the 2nd photo, has an inner bore of 3/4" and looks correct. Cannot see how it can seal on a shaft if 1/2" without our mystery plastic bush/auxillery seal thing - seen in the middle. 2nd photo also shows how it is assembled on the shaft. Ist photo shows our mystery object in profile
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Re: Timing cover/dynamo leak 55 G9

Postby ajsph » Sat May 16, 2020 4:41 pm

Her are some photos of the parts you need, the collar for the inside of the oil seal has to be a good fit on the shaft, or oil will seep between shaft and collar, in the dynamo
Poul
DSC01881_1.jpg
DSC01880_1.jpg
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Re: Timing cover/dynamo leak 55 G9

Postby Mick D » Sat May 16, 2020 6:15 pm

Hi

Not too easy to see from the photo, but isn't that seal on the wrong way around? The garter spring should be facing the timing chest shouldn't it?

Are you missing collar 'R' which has been, 'poorly' substituted with that piece of plastic?

Regards Mick

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Re: Timing cover/dynamo leak 55 G9

Postby Oggers » Sun May 17, 2020 11:31 am

Mick

Yes its in the wrong way, but its just to show the bevelled edge on the inner face of the seal which "mates" with the black bevelled edge of my plastic bit. However, given Poul's photos it does seem clear I appear to have inherited a PO bogde, and I need the collar - hence perhaps the source of my original leak. The plastic bit does look well made though. Odd to imagine why it was there...

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