Cannot stop oil coming out of dynamo interface with timing case

[Roadrocket649]

Hi Hubie

I think you mean between the Dynamo Drive sprocket, and the casing which BSA-Bill & the Draganfly BSA catalogue show as 67-0708, so we agree with you

For A10 Boy: Yes the crancase breather was thoroughly cleaned out and was rechecked a couple of days ago

I could not see how the cork seal, with one face pressed against a non moving crankcase, and the other against a moving sprocket could survive, but I have one on now and looking hopefully forward tooil free shoes and silencers.

Once again, many thanks to you all

Roadrocket649

[Topdad]

Good morning everyone, this is really "doing my head in " Andy's thought could hold the answer but boy oh boy that'd be some amount of oil to get up there. When mine was wet sumping after a few days if I forgot to drain it it would blow out via the primary case ,a neat innovation on the part of BSA engineers to ensure that the clutch etc was lubed !! but it didn't get to the dynamo part of the timing case however with these bikes it would be a brave man who said it couldn't happen .Can I  just please ask that we're not left in limbo over this and when sorted let us know what the hell was causing it!! best wishes Bob.

[Brian]

Just to clear up any confusion here is a scan from the parts book, the seal or cork ring in question is the part numbered 76. Its part number is 67-708.

[t20racerman]

Just to clear up any confusion here is a scan from the parts book, the seal or cork ring in question is the part numbered 76. Its part number is 67-708.

I've always had one fitted too Brian and it has never broken up yet.

However, I also once had oil filling up the dynamo chain case and it was when I'd changed the inner timing case cover for another one. I bought an RGS type one (with the tacho drive on the leading edge) so that I could run a tacho and on the next long run I seemed to have oil pumping out everywhere around the dynamo! I stripped it and investigated and found that.... (pause for tension!  ) the special scrolled bush for the timing gear had been replaced by the previous owner with the wrong bush - one scrolled all the way through. The revolution of the timing gear was therefore slowly pumping oil into the dynamo chain area.
I changed the bush for the one on my old casing, and the problem went away.

Sounds to me that you should examine that bush carefully....

[A10Boy]

That seal number 67-708. I've not fitted one to my current A10, never had one on any other A10 either and never had oil in the dynamo chaincase. Next rebuild, I might fit one, but its obviously not doing a lot.

[Roadrocket649]

Hi Guys

Excellent news

The cork seal was fitted, and the oil discharge immediately stopped

Ran 100 miles now without a drop coming out

Many thanks guys

I tend to think the bush is not scrolled, and as the engine has just been totally re-build, it will have to wait till the next time - hopefully in 20 years or 200,000 ,miles time

Not sure whether the scrolled bush was a BSA introduction after the bikes were originally released

Roadrocket649

[t20racerman]

Glad to hear its all sorted now.

[A10Boy]

I've bought one of those 15mm wide "Dynamo Regulator" belt drive kits. There's a cork washer in the kit and the instructions say soak it in oil overnight to soften it - so I will even though I don't have one fitted now and it's never leaked oil.
It will be good to get rid of that rattley chain, even though I fitted a new chain at the last overhaul, I could never get it set quite right, it had tight and loose spots so I had to set it right at its tightest which made it too loose as it turned over. I suppose that was un-even wear on the sprokets. Has anyone fitted the 15mm wide belt, what do you think of it ?

[alanp]

I've bought one of those 15mm wide "Dynamo Regulator" belt drive kits. There's a cork washer in the kit and the instructions say soak it in oil overnight to soften it - so I will even though I don't have one fitted now and it's never leaked oil.
It will be good to get rid of that rattley chain, even though I fitted a new chain at the last overhaul, I could never get it set quite right, it had tight and loose spots so I had to set it right at its tightest which made it too loose as it turned over. I suppose that was un-even wear on the sprokets. Has anyone fitted the 15mm wide belt, what do you think of it ?

Yes, I've fitted the one from Dynamo Regulators. I didn't fit the cork washer though because I had previously used one on another type of belt drive kit and it broke up, possibly being the cause of tooth failure of the belt due to bits getting onto the teeth.
I had the occasion to take the outer timing side cover off the other day and there wasn't any oil coming into the belt drive chamber and the belt was fine so I'm happy.
Concerning the washer, if you are going to fit it make sure it isn't much compressed when you pull up the drive pulley onto its taper or it will likely disintegrate depending on the make up of the cork in the washer and how much squeeze there is on the cork. DG recommend reducing its thickness with abrasive paper so that there is no compression/feel of the washer when pulling up the pulley.
If you don't have a leak there now I wouldn't fit the washer, after all, the synchroflex belt (assuming it is marked synchroflex) can handle oil anyway.

[A10Boy]

That's a very good point, there's no oil now so I wont fit it just in case it breaks up. The belt is a syncroflex.

Cheers

[A10Boy]

I fitted the belt kit, didn't fit the cork "seal" supplied in the kit - guess what..............

[A10Boy]

Yup, you guessed it....

Now fitted the supplied cork washer seal and no oil. Strange that with the old chainwheel and no seal there was no oil in there, but when I fitted the belt kit there was. I can only assume that the belt drivewheel center stands further away from the inner bush and allows some end float which pumps it out. Fitting the cork stopped the end float on the idler shaft. I cant help thinking something better than cork would be advantageous.

[t20racerman]

I cant help thinking something better than cork would be advantageous.

I'm all for modern materials and happily use uprated bits where available, but the cork washer works perfectly so I've never bothered looking for an alternative.
My last one ran happily for over 20,000 miles, without leaking or falling apart. 

[muskrat]

G'day Andy,
                have a look here http://www.a7a10.net/forum/index.php/topic,3501.0.html a proper seal by Brian and Richard.
Cheers

[A10Boy]

Thanks for that Musky.

I agree with this, I was thinking along these lines myself.

This leads me to think that if the dynamo is not sealed against the inner cover crankcase pressure will try to escape that way taking oil with it.