Author Topic: Timing side oil leak  (Read 983 times)

Online Ratchet Richard

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Timing side oil leak
« on: 27.08. 2020 04:45 »
Help needed please.  New to BSA A7 only done 30 miles on a newly rebuilt engine (not rebuilt by me).  I am trying to do about 50 miles before changing engine oil.
When I got home and parked the bike up I noticed a quite bad oil leak coming from the front right hand side of the engine. This oil leak stopped when the engine was stopped other than residual drips but started again when I started the engine.  It looked as though it was coming from somewhere near the dynamo area.  Took the outer timing case off to see if anything had come lose but can’t see anything obvious.  There seemed to be oil in the front compartment that has the dynamo belt drive, is this normal and could the oil be coming out from behind the out cover. 
I checked the inner cover screws which seemed tight.  As I am new to these bikes and only an amateur mechanic I thought I would ask here before going any further.
Thanks
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Online muskrat

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Re: Timing side oil leak
« Reply #1 on: 27.08. 2020 05:46 »
G'day Ratchet.
Wash the area and start the motor, having a good look at where the oil first appears.
It could be coming from the pressure relief valve (the big hex with a smaller hex in the center). Inspect both the inner and outer cover for cracks or bad sealing surfaces.
The problem could also be oil getting past the idler shaft bush and seal (felt washer) behind the dynamo driving sprocket. Then escaping where the dynamo butts into the inner case (there is a cork gasket there).
Cheers
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Offline Swarfcut

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Re: Timing side oil leak
« Reply #2 on: 27.08. 2020 09:27 »
Hi Richard. To add to Musky's advice, as standard the dynamo is chain driven and runs in grease.  There is felt or cork washer under the large dynamo drive gear to act as a crude seal. Your bike has a belt drive? an aftermarket mod, and oil should not be in that compartment.

 The dynamo seals with a large cork washer against  the inner timing cover.  After tensioning the  belt, press the dynamo against the  inner side of the cover to trap the cork washer and seal this joint.

  The oil pump runs in its own little oil filled compartment, so a cup of oil here is normal.  Gasket faces failing to seal is common, the mating surfaces are narrow, and there are locating dowels which can bottom before clamping the gasket, especially on engines built from a collection of parts, and dowel locations full of old jointing compound.

   Removing the inner  timing cover means removing  the dynamo drive gear....the cover will come away complete with the retaining bolts undone, but the idler timing gear needs to be replaced with the timing marks aligned, and so needs to be separated from the cover unless you have X Ray eyes. A better scheme is to remove the dynamo drive gear first, and check if the seal has been fitted. Then removing the inner cover will not disturb the timing gears if you are careful.  Make sure the cover retaining bolts don't  bottom.....incorrect lengths and old jointing compound at the bottom of blind holes all contribute to a lack of clamping force on the gaskets.

 Swarfy.
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Offline Minto

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Re: Timing side oil leak
« Reply #3 on: 27.08. 2020 09:40 »
If you remove the inner timing cover, keep some thumb pressure against the end of the  idler pinion shaft to stop it coming away with the cover, this will maintain your correct valve timing.
I too have a leak on the timing case, among many others.
Jase
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Online Ratchet Richard

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Re: Timing side oil leak
« Reply #4 on: 27.08. 2020 09:54 »
Thanks swarfy, I will have a close look at the dynamo seal. When you say “after tensioning the belt, press the dynamo against the inner side of the cover to trap the cork washer and seal this joint“ how would you actually do that? I have attached a photo of what it looks like at the moment.  Just not sure of how I would press the dynamo against the cork washer with tension on the belt?
Thanks again for the advice.
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Online Ratchet Richard

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Re: Timing side oil leak
« Reply #5 on: 27.08. 2020 10:02 »
Thanks Muskrat will follow your advice in conjunction with swarfy, I don’t think it is the pressure relief value as I did check that area. 
Noted Minto don’t want to have to start messing around with timing gears at this early stage of ownership if possible.
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Online Greybeard

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Re: Timing side oil leak
« Reply #6 on: 27.08. 2020 10:07 »
The dynamo is clamped by that strap over the top. You loosen the strap a little then rotate the dynamo body to tension a chain originally, on your bike, a belt. While tightening the strap push the dynamo firmly against the back of the case where there is a large cork washer which should seal the connection.

I think the belt needs no more slack than to be able to twist it to 90°. Can a belt guru confirm that please?

There is some discussion about running a belt in grease, but I think the balance of opinion on this forum is to run it dry.
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Offline Swarfcut

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Re: Timing side oil leak
« Reply #7 on: 27.08. 2020 10:18 »
 

  Richard, looking closely at the picture there seem to be no bolts retaining the inner cover to the crankcase. There should be four, two along the top edge, one in the boss in the centre of the belt compartment and one below the magneto ATD unit cog. All the other bolts pass through the inner cover.

  The dynamo is held in place by a metal strap, and simply rests in the cradle cast in the crankcase. With the strap loosened off, the dynamo body can be rotated to tension the belt....the shaft is not central to the body.  The dynamo can also move sideways, pulling it towards you will trap the cork seal and align the belt pulleys. Once happy with its position, retighten the clamp to secure in place. Put a little mark so you can see if the dynamo moves over time, then retensioning the belt is a matter of realigning the mark, without the faff of removing the outer cover again. This also gives a visual check that the belt remains as set.  Works just as well with the chain drive.

 GB was a little more lively on the keyboard.....

 Swarfy
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Online berger

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Re: Timing side oil leak
« Reply #8 on: 27.08. 2020 12:40 »
rightly or wrongly I push the dynamo towards the case as hard as possible then gently clamp it up to the case, BUT! I sometimes find tightening the clamp up moves the bl**dy thing, then it's start again *bash*
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Online Greybeard

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Re: Timing side oil leak
« Reply #9 on: 27.08. 2020 12:50 »
rightly or wrongly I push the dynamo towards the case as hard as possible then gently clamp it up to the case, BUT! I sometimes find tightening the clamp up moves the bl**dy thing, then it's start again *bash*
Yup, they all do that sir!
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Online orabanda

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Re: Timing side oil leak
« Reply #10 on: 27.08. 2020 14:22 »
Tip for holding the dynamo when tightening the strap: The lug on your typical light pressed metal "C" spanner supplied with rear shock absorbers (Girlings, Konis, etc) can be hooked into the upper screw recess in the dynamo flange. I have found you can then stop the dynamo from rotating whilst tightening the clamp. Also good for tightening or loosening the belt (chain?) adjustment.

Richard
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Offline mugwump

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Re: Timing side oil leak
« Reply #11 on: 27.08. 2020 14:38 »
I seem to recall a while ago somebody reported that they had discovered that the idle gear bush had been scrolled incorrectly and therefor allowed oil into the dynamo drive compartment. I know its a long shot but how else would oil be entering said compartment.
I don't imagine the cork washer would prevent oil getting past as its main function is to control end float.
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Online RichardL

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Re: Timing side oil leak
« Reply #12 on: 27.08. 2020 14:41 »
As for identifying the point of leakage, you can try wrapping the timing case with some absorbent material that reveals the location. Here's a link to my such effort:

https://www.a7a10.net/forum/index.php?topic=11106.msg83847#msg83847

Richard L.
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Re: Timing side oil leak
« Reply #13 on: 27.08. 2020 14:43 »
Avoiding daft comments like your engine is in upside down, I can't see any screws for the inner casing as Swarfy says either.

While you're in there, check those oil pump nuts are nipped up too.
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Online Ratchet Richard

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Re: Timing side oil leak
« Reply #14 on: 27.08. 2020 15:00 »
Thanks for all the advice guys.  I have been taking it all in.  I have noted that the outer casing Allen screws are not quite what they should be. The three small ones are right but I seem to have one very long one in the bottom aft position and then all the rest are just long.
I have ordered a set of proper screws from Draganfly and a two new gaskets.  I will wait until they have turned up before processing. 
Swarfy and Metalflake you are both very observant, the four inner casing screws are not in place. I removed them, but then, thankfully got cold feet about going any further before consulting this forum.
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