The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: Roadrocket649 on 20.06. 2011 09:31
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Hi Guys
I wonder if you can help
Bike : BSA A10 Super Rocket
Year: 1958
I have oil coming out of dynamo interface with timing case which ends up covering my foot and silencer
I have re-set the dynamo, tightening the holding bolt till it is gripping the dynamo, and then tapping with a hide hammer to ensure it is pressed firmly against the Timing case
- No Joy
I sealed the inside of the housing interface with the dynamo with loctite 5910 sealant, and tried again
- No joy
A friend advised that there should be a cork seal (67-708) between the dynamo driving sprocket and the casing, to stop oil leaking out of the bearing
(I see no mention of this cork seal in the Haynes Manual I have (maybe I have missed it ? but it is in the Draganfly Catalogue)
Is this correct?
As that would mean tightening the Dynamo driving sprocket (which is turning)against the cork seal which in turn will be pressed against the casting (which is static) holding the bearing through which the drive sprocket shaft is retained
Surely the cork seal will just disintegrate
Could anyone help please
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I would investigate how the oil is getting into the dynamo chain chest as its not supposed to be there, the chain runs in grease not oil. Could be that the outer cover gasket was damaged during assembly allowing oil in. The cork gasket goes between the dynamo face and the inner timing cover to stop grease leaking. There is no seal under the dynamo drive sprocket.
HTH
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G'day roadrocket469,
The bush in the inner cover that the shaft goes through should have a scroll in it to direct oil back into the motor. Does yours have this scroll? Never had much luck with those cork or felt seals, get eaten very quickly. Neither of my A's have one and never have more than a teaspoon of oil in the dynamo chest.
As A10Boy suggests the gasket could be the culprit as well.
Low melting point grease for the chain, a little oil wont hurt if the dynamo is sealed well.
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Hi Guys
Muskrat: Don't know about the scroll - a toolmaker in the BSA Owners Club assembled that part of the motor, and he is on holiday so I cannot find out
A10Boy: I have used a normal gasket with loctite 5910, and then just Loctite 5910 - no change - assembled three times with same result - oil leakage
Certainly there is no mention in the Haynes manual of a cork seal, but in the BSA Draganfly catalogue it mentions the cork seal 67-708 as an Idler Pinion Oil seal.
I used grease in the dynamo drive sprocket compartment, and had agrease / oil combination dripping out
I, like yourselves cannot see where it is coming from, as there appears to be sealant on the oil pump/ dynamo drive sprocket interface
I am wondering that, as there are signs of the chain having fouled or jamed the lower side of the compartment, whether this has bent the lower end of the compartment down, so oil from the oil pump area can access the compartment
Is the oil pump area full of oil for the pump to pump, or is this just residual seeping out of the pump?
The pump has brand new parts ex SRM
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HI ,there defo a cork washer on the end of the dynamo where it butts to the crankcase and as this is one of the very few places that I've never experianced any oil leaking from on my A10's I would think you have a damaged /warped timing case ,try it on a piece of glass ans see if it sits level or proud ,some previous owner could have overtightened it on one side and actually bent the case, I've seen 'em really out of line, hope that helps best wishes Bob
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there are several possible causes for this, first oil should not be in the dynamo compartment that should be running in grease only, yes there should be a cork gasket on the dynamo but normally it does not need any sealing compound. assuming the inner and outer timing cases are flat and mate correctly and have a decent gasket there is only one way oil can get in and that is via the drive shaft, this can be down to a worn shaft or bush, the bush should have a grove that keeps the oil in the engine area and out of the dynamo, but sometimes i have seen a lot of end float on the shaft which does not help as the only thing that controls that is the thrust face on the bush in the timing case and the one in the crankcase, in the past i have removed this bush and fitted a needle roller bearing which makes this a real problem and then had to modify the inner timing case to take an oil seal which fixed it .
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With both covers off the motor mate them together and have a look from the inside to check for misalignment (damage). Remove the sprocket (with a suitable puller or place cover on blocks of wood and give the shaft a sharp tap with a brass dolly *eek*) and idler pinion shaft from the inner cover to check for scroll in the bush. Check the shaft in the bush for fit (easy spin, no wobble). If all that checks out OK buggered if I know. Like I said if the scroll is working there should be no or very little oil in there even without the seal.
Take care with the timing marks on assembly.
Cheers
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Remember it's a reverse scroll. Maybe somebody got it the wrong way in the past. They are quite effective so i would be investigating this.Lots of different makers use this system with no problems, but i have heard of people getting the scroll in the wrong direction, which would pump it out.
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but i have heard of people getting the scroll in the wrong direction
*red*,ah that would be me then Wilko.
There is a cork seal in the gasket set for behind the dynamo sprocket, can't think where else it would be for, and of course a big cork washer sits between the dynamo and the inner case
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There is a cork seal in the gasket set for behind the dynamo sprocket, can't think where else it would be for, and of course a big cork washer sits between the dynamo and the inner case
I find that the cork seal and the felt disintegrate so run without either and precious little oil gets in that chamber. Guess my scroll must be correct. Can't say I've ever noticed it though. The next time I have the misfortune to take area apart I'll look. The gap the seals have to fit will vary though with different part machining, expecially the sensitive taper so, sod's law, it's likely any seal will either be too loose or get squashed.
Alan
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Thanks Guys
Much Appreciated for all your thoughts
Roadrocket649
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One other thing, check your crankcase breather is working correctly.
One more other thing, does it wet sump? Could be that this is where the over pressure is forcing oil out, does it leak for 10 mins then stop or does it leak all the time? Check oil tank level before and after running, if the level was right after a run, but is low before start up, dont fill it until you have run the engine for 10 minutes. My a10 hasn't got a seal behind the dynamo drive sprocket and it doesn't fill the chaincase with oil. I dont believe there should be one there anyway.
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I dont believe there should be one there anyway.
Best panto voice "Oh yes there is"
it's part no 67-0708
[quote ]it's likely any seal will either be too loose or get squashed.[/quote]
Well wether it's needed or not is debatable but BSA thought it should be there and yes it will get squashed a little and once squashed will be a better fit, all the ones I've had were squashed certainly but only one ever broke up and that one was supplied for a belt drive kit but not I hasten to add by SRM or any other firms that make them, as a matter of fact SRM supplied a replacement that has not broken up.
One reason they might break up would be dependant perhaps on just where about on the idler shaft the idler gear is,it is key on but is only a tight fit, if for example the taper or sprocket taper was worn excessive torque on the dynamo sprocket nut to pull it onto the taper could pull the shaft through the gear and leave too much room for the cork washer, OTOH if the gear was not far enough through the shaft it might be that the opposite was the case and the washer got really squashed to much before the taper was tight.
Not sure if that reads just the same as it sounds in my head lads, hopefully you understand what I mean.
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I know what you mean Bill. i always use the hot gear/frozen shaft method and loctite, making sure it's in the right spot.
Andy might have a point re wet sumping.
Cheers
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G'day,
I'm far from the foremost expert here but has anyone mentioned the cork seal behind the large sprocket that sits up against the case? That one I know must be there.
Cheers,
Hubie.
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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
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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.
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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.
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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! *smile*) 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....
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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.
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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
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Glad to hear its all sorted now.
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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 ?
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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.
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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
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I fitted the belt kit, didn't fit the cork "seal" supplied in the kit - guess what.............. *eek*
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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.
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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. *smile*
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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
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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.