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Sealing the primary chaincase

I'm about to fit a new primary chaincase gasket & would appreciate any tips for making it all oil tight.
I don't want to use silicone or any of that stuff so it's down to old school ideas I suppose.
Sorry, I'm sure there's stuff on here already about this but I couldn't find it with the search.

Re: Sealing the primary chaincase

Hi Bob,

Is this for the pressed metal BSA chaincase?
I don't think that there's much you can do besides a new cork gasket. I think most people will be using silicone as well.

Re: Sealing the primary chaincase

I use silicone...However, one 'trick' told to me many years ago by an old boy (I'm one of those now:laughing: ) was to melt some tallow and pour it into the chaincase before putting the oil in...The tallow solidifies along the bottom of the case improving the seal....

I'm not even sure if you can still buy tallow from butchers but one of the greases you can melt or perhaps 'Linklife', the boil in the can chain lubricant, could be substituted...

All of those methods would create a bit of a mess in the casing and make extra work if you have to remove it...I tried the tallow and it did improve matters, but that was in the days before silicone sealants...

Also, some of the leaks are from the gearbox mainshaft felt seal mounted in the sliding plate located in the back of the inner casing and the above does nothing to stop that...

When silicone sealants appeared I soon went for those and don't really see the reasoning behind being 'old school' in that regard....Ian

email (option): ian@wright52.plus.com

Re: Sealing the primary chaincase

I'm "old school" and we always used to use grease, or at least I did with good results. Mt mates used that horrible red hermatite or whatever it was that really looks awful. So use grease on both sides of the gasket. If it doesn't work youv'e lost nothing.

Re: Sealing the primary chaincase

First of all knock out all of the dents in the outer from the bolts being done up too tight so the case is flat.
Nest get some big washers to spread the load from the bolt heads.
I use 1/2" (od) ones which need to be ground so they do not foul on curves in the outer case.
Grease on the gasket is a good idea and use a soft grade of thick cork to make the gasket from.

email (option): bsansw1@tpg.com.au

Re: Sealing the primary chaincase

First, I degrease the inner cover, and use silicone to glue the gasket in place. Then slightly grease the outer cover, put silicone on de gasket and put the hundreds (or so...) tiny bolts in place, starting at the underside. No leakage anymore, and you can still easily remove and replace the outer cover...:relaxed:

Re: Sealing the primary chaincase

Hans WDM20 58764
First, I degrease the inner cover, and use silicone to glue the gasket in place. Then slightly grease the outer cover, put silicone on de gasket and put the hundreds (or so...) tiny bolts in place, starting at the underside. No leakage anymore, and you can still easily remove and replace the outer cover...:relaxed:
That is how I do it.
"Then slightly grease the outer cover" - I use copper grease/paste.

email (option): michasteinmann@gmail.com

Re: Sealing the primary chaincase

Thanks for all these replies folks. Yes, I should've mentioned that it's a WM20 pressed metal chaincase, in reasonable condition.
I've used grease before with fair success, but the current gasket's pretty sodden & owes me nothing so I thought I'd try another way. I've read of using tallow, I think it was favoured by AMC riders?
The reason for going "old school" basically means not using silicone, as trying to separate the two chaincase halves tests even my formidable armoury of expletives. I'd considered doing one side only as you suggest, Hans & Michael & am pleased to hear of your success. Think I'll try that. And I might buy myself some washers.

Re: Sealing the primary chaincase

You can get tubs of tallow from decent plumbers merchants. For use in lead work its still unbeatable.

If you use silicone, oil the detachable side of the case before you fit it, should then come off OK.

Thank you Ian, as one of the "Old Boys" I was advocating the use of tallow years ago on the Matchless forum and got endlessly ridiculed for it [just one of the reasons I quit].

An equally good substitute if you can get enough is that bullet proof grease used on WD spares; the joy of using grease of any kind is that if heavy enough, viz tallow, should you need to part the cases in the field then by warming it up the grease will melt and reseal.

Re: Sealing the primary chaincase

Hi Bob,

In order to seal it all,
You would need a paper gasket between the block and the inner primary chaincase, (I used "Shellac" there)
Then a big round felt washer, 2 washer gaskets on the screws of the sliding plate (Made of Klingerit or something like that)

When I installed the outer cork gasket, I was also going "Old School" and sealed it with Shellac Compound.
(Permatex Indian Head Gasket Shellac Compound or something close)
And I run the primary wet without a drop of oil drip.

Of course, the faces of the primary case inner part and its cover should be in a reasonable straight condition...

Noam.

Re: Sealing the primary chaincase

On any cork gasket only grease is needed, unless the joint is really badly distorted.

Re: Sealing the primary chaincase

I like Ken's idea of using cosmolene. I'll try that.

email (option): cas.vanderwoude@gmail.com

Re: Sealing the primary chaincase

Noam, Ken, Cas
Yes, there's the back of the inner casing to be considered but this was all done ?properly? when the bike was assembled & seems OK. Though I may treat myself to some new gaskets around the footrest.
I'll try the silicone & grease.

Hans & Michael
Does greasing the outer cover before putting silicone on the gasket allow the cases to be separated fairly easily?

Re: Sealing the primary chaincase

Yes, they separate easily Bob! I only watch the order of assembly, doing the bolts from down upwards, and for disassembly I start from the top downwards.

Re: Sealing the primary chaincase

I use synthetic grease and have no leaks. No silicone is needed. Make sure the cover is flat, use a new gasket and don't over tighten the screws. Petroleum based grease works but does not last as long as the oil will dissolve it over time.

Re: Sealing the primary chaincase

Hans & Bruce
Thanks again. I've forged ahead & used silicone on the outer cover & grease only on the inner. On my bike the gasket always comes away with the outer piece on dismantling so I've made that the semi permanent joint. If it's still a leaker I should be able to work out which joint is failing. The silicone needs 24 hours to cure so I haven't filled the case yet.

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