Leaky pressed steel chaincase

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Leaky pressed steel chaincase

Postby simondewings » Mon Feb 09, 2015 11:49 am

Has anyone managed to find a real fix for this.
I have a 55 G3L bitsa and CANNOT stop the chaincase leaking.
Not aiming for authentic looks so even a conversion to O ring chain is a thought. Anyone tried that?
Thanks for any input.

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Re: Leaky pressed steel chaincase

Postby clive » Mon Feb 09, 2015 12:47 pm

The club spares scheme (AMOC parts from the home page) now sells a seal which has had good reports although I have not tried it myself. However not all the oil is usually coming from the seal, it also leaks from the gearbox hole and the dynamo hole. Finally if the bore/rings are a bit tired then due to blow-by the crankcase breather sends out an oil mist which tends to deposit on the back of the chaincase.
As for the o-ring conversion, these tend to be wider than the original chains and I think you may have problems with chains clashing and/or clearance around the back of the clutch basket and the inner chaincase, also there is question of oiling to the clutch rollers.
clive
if it ain't broke don't fix

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Re: Leaky pressed steel chaincase

Postby saltbox alf » Mon Feb 09, 2015 2:36 pm

Here is the gospel according to ITMA and with the new club seal even better, but you find all possible leak points covered here.

Here follows ITMA's gospel of the tin chain case. Worth reposting for all as it points out the various places the case can leak from.
I have followed this procedure and have a fairly oil tight case, the odd drip as expected.

There are 9 holes in the tin chaincase where oil can potentially leak;
around the mainshaft boss
the three bolt holes
the dynamo hole
the centre stud hole the gearbox mainshaft hole
the joint itself
most of these leaks are attributable to causes other than poor design, these cases are not as bad as they are made out to be and with care can be made almost 100% tight.
Strip out all the drive side and clean it all off, starting at the main shaft boss, this area is often damaged where a loose back half has been fretting on the ally casting, next the three screw holes, are they damaged or spilt? although the bolt heads are 2BA the threads are 0BA NOT 1/4 BSF which is very similar to the eye, 1/4 BSF can be used if need be but the clearances will need to be carefully checked, I have on occasion used cheeseheaded screws here, drilled for wire but its fiddly.
What is necessary is that the screw holes be absolutley cleaned out,with the appropriate taper tap, or an aerosol cleaner. you will be amazed at the clag that comes out,this will stop the screws from using all the thread length, and/or all the old oil will get hydrauliced past the threads thus rendering useless the loctite you`ll be using later.
Do not bother with the useless locktabs, use a shakeproof washer and loctite, I`ve not had one drop out yet.
assemble the back case to the crankcase temporarily, but tight, then carefully measure he distance between the rear of the case and the engine plate, I`ll bet they are not the same as the spacer length; make up the distance some how,so that the case does not bend when the final nut is tightened. Repeat this process with the outer case on,make up all the spacings so that there is no compression of the cases at this point.
You can use thin fibre washers at these points if you wish.
With both halves offered up but not tight there should be no gaps at any point around the rim, if there are then you`ll need to bend/twist/ hammer them back together so that they are touching all round the rim.
The dynamo hole is not as much of a culprit as it is made out to be either, make up a washer from any old felt about 1/2 " thick, 3" dia. and with a 2" hole, the greater benefit of this is to keep things like water out, the same goes for the tip earlier about the leather washer on the back of the gearbox hole.
The problem with this area is the damage that is often to be found here, wear on the back from the chain,usually because the case has not been lined up, the inner dished oil deflector behind the clutch has been flattened or distorted, or these days has been filled up with epoxy paint, so that the oil overflows onto the gearbox shaft, although centrifugal force should keep the area behind the clutch reasonably dry.
Take a look at the oil trough above the dynamo hole at about 11o/c, is it there? or damaged/ earlier cases did not have this, and get mixed up, the idea of this trough was to catch oil before it exited out the dynamo hole and deflect it onto the chain.
before you fit the inner case for good, slip a bit of tube 4 or 5 ins long over the breather, thus any oil coming out here will be deflected away from the back of the case, thus no confusion.
fit the gasket to the mainshaft boss and do up the 2BA set screws as described, then if you wish run a bead of silicone around the rim, offer up the outer case carefully and holding it in place do the centre nut up finger tight only, then on goes the rubber, and the band, do the band up and lastly the centre nut, there should be NO compression under this nut.
Run some warm tallow into the case, which will set immediately, then top up with 30 grade oil to just below the bottom of this hole.Chain should just touch the oil.
I prefer to use a leather washer on the filler cap.
The little bracket that runs from the battery carrier to the top rear on some models should fit without forcing or pulling on the case.
Which if under stress can also cause a leak.
Allons-y, amis de Matchless et AJS

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Re: Leaky pressed steel chaincase

Postby simondewings » Tue Feb 17, 2015 10:21 am

Wow, Thanks very much for such detailed responses. I'll get to work checking all those potential points.

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Re: Leaky pressed steel chaincase

Postby sjr » Fri Mar 06, 2015 7:42 am

I can personally vouch for the new design Club Spares Scheme seal.
Its made of foam which will adapt to fit almost any gap.
Tried it on my badly warped cases and they are now oiltight.
The fitted seal doesn't look any different from standard from the outside.
Really easy to fit too.

Steve

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Re: Leaky pressed steel chaincase

Postby 56G80S » Thu May 07, 2015 8:08 pm

Thanks for the report on the new seal, mine aren't too good since the long ago clash between primary and dynamo chains resulting from no retaining strip.

Next time I order from Spares Scheme I think I'll invest in advance of need.

Johnny B

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Re: Leaky pressed steel chaincase

Postby thornebt » Wed Feb 24, 2016 10:56 am

I'm in the process of refitting my chaincase. The lengthy post with all the tips is invaluable - thank you Saltbox Alf. I'm a bit confused about the tallow however. I've heard of this but never known exactly what it is. I can see both hard and medium white tallow on Ebay which is used as a lubricant for pulling cables through conduit.

I'm guessing that I gently heat the tallow and with the large clutch dome removed run it along the bottom half of the join. Clearly this won't be very easy for the front lower half of the case. Is white tallow definitely the right stuff and would hard or medium tallow be best.

Finally but less importantly, what further uses are there for the large amount I will have left over from my 0.5kg tub? I saw somewhere that it can be used as a chain lubricant but I was thinking of using Castrol LM or similar on my magneto chain.

Cheers. Bruce.

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Re: Leaky pressed steel chaincase

Postby Rob Harknett » Wed Feb 24, 2016 12:04 pm

We used to use Tallow on moulds used on heat presses to manufacture shaped plywood. ( e.g old type TV cabinets with rounded corners, the inner supports for suit cases, tennis racquet frames etc. It helped stop glue adhering to jig moulds. Also used it to stick brown paper in spray booths, this kept them clean as, the caked with paint paper could easily be removed and replaced. Its Animal fat. The factory would smell of roast beef, when used on the heat presses. Horrible smell if it was rotten. I guess cooking fat or Lard is a more refined product of animal fat. Often used mothers Lard on my bikes when a teenager, instead of grease.

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Re: Leaky pressed steel chaincase

Postby JimFitz » Wed Feb 24, 2016 3:14 pm

Tallow is a great tip but really a last resort Bruce. I found that the new seal, carefully fitted, coupled with the other tips from Saltbox Alf should do the trick. I found that you sometimes need to experiment with extra washers on the central spacer to get the correct bite if you go for the new type seal without distorting the chaincase. The seal is a T section so you need to allow a small gap between the inner and outer cases to accomodate it.

Jim
Too old to Rock and Roll but too young to die.

1952 G80 rigid, 1960 G12 DL / Watsonian Monza, 1954 G80S.

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Re: Leaky pressed steel chaincase

Postby thornebt » Wed Feb 24, 2016 4:05 pm

Thanks Jim. I've got a new Buckingham seal and my chaincases line up really nicely to start with. So I'll give the tallow a miss and will make a good job of fitting the seal, ensuring I use washers to get the right fit. Cheers. Bruce.

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