G12 Primary Transmission

lawrence · Post by **lawrence** » Sun May 07, 2006 9:57 pm

There should be a gasket. Jampot Spares sell it. I use one but the case leaked just as little when I didn't use a gasket. The blue is probably Hylomar sealant, good stuff easily the equal of Wellseal. Rolls Royce use it .

Without a gasket use Hylomar or Wellseal. If you fit a gasket just grease it both sides before fitting and you should not need sealant, the case comes apart again easily and the gasket can be reused indefinitely. Sealant and gasket on the primary case = new gasket every timeEdited by - lawrence on 07 May 2006 9:01:07 PM

itma · Post by **itma** » Sun May 07, 2006 10:55 pm

When making the boss for the drain plug, there is very little metal there.
Think about making a top hat shaped boss to go in from the inside,this will give you a bit more metal to work with. You can then drill/ tap this out as per original. do not overlook he usefulness of stuff like `luminweld` for these types of repair. Safer than regular ally welding

RogerJ · Post by **RogerJ** » Mon May 08, 2006 9:17 am

I had a similar problem (amongst others!) on my chain case and Luminweld worked a treat.

paul knapp · Post by **paul knapp** » Mon May 08, 2006 9:57 am

Hi Martin, another repair method you could consider is to fill in the hole with a low melting point aluminium alloy (380C) rod, then drill & tap to the correct thread form. You can use a propane torch for this work, since the melting point of the aluminium case is approximately 660C, there is neglegable chance of melting the parent metal.The Brinell hardness is 80, which is tougher than aluminium. No flux is reqd., just a clean surface.The rods I use are made here, but I would say there would be an equivalent available in GB.
Regards Paul.
...................
Have a look at this to see what I am goin' on about
..http://www.durafix.net.au/
Edited by - paul knapp on 08 May 2006 10:51:32 AM

RogerJ · Post by **RogerJ** » Mon May 08, 2006 4:30 pm

The product Paul describes sounds the same as the Lumiweld - see http://www.lb-restoration.co.uk.

I should also add that you can get the tap and drill for the chaincase plug from Tracy Tools (http://www.tracytools.com)Edited by - RogerJ on 08 May 2006 3:31:58 PM

MartinL · Post by **MartinL** » Tue May 09, 2006 11:43 pm

Again thanks to all for the replies.

What I have done is drill the coarse thread from the chaincase with a 13mm drill (apologies for this metric stuff but it was available). I decided Lumiweld was a step too far for me right now so I then turned up from a piece of ally a flanged insert which was a gentle push fit into the hole, and pilot drilled this. Inserted the new plug with the flange of about 3/4 inch diameter outermost, using plenty of loctite, and peened it over on the inside. I've now drilled and tapped it 3/8 UNF. It looks a well engineered job. When Jampot Spares deliver the new springs and primary chain I'll test it out and report back.

(I must also thank the local Tech College for the use of their lathe.)

Regards

Martin

MartinL · Post by **MartinL** » Wed May 10, 2006 5:21 pm

I'm back again. Jampot spares returned the spares I ordered within 24 hours, incredible service, what a great bunch.

The clutch springs look no different to the ones I already have, I've obviously fitted them but I don't think this is the cause of my clutch slip. The plates that came in a box of spares with the bike look far better than the ones fitted so I have fitted them instead and rebuilt the clutch. It all seems to operate as it should, and I was feeling pretty smug at this point.

The old primary was well and truley buggered with the gearbox way back in the slots. Even so it was loose and causing damage to the inside of the primary cover, so a good thing I have taken it down. I guess I should replace the engine sprocket and clutch basket, but that can wait for the winter.

"Be prepared for some fun when you fit the new primary" said Alan in his intial response to my query. I think I now understand what he means. Any tips on how to move the gearbox forward, other than get a bigger hammer? I've slackened the nuts as required by the manual, which makes no difference, I guess I need to loosen the rear chain too. I have Norton wheels and the manual is silent on how to adjust these. Is this a case of slackening off the bolts on either side and then loosening the adjusters?

Any hints, tips and advice welcome.

Regards

Martin

Don Madden · Post by **Don Madden** » Wed May 10, 2006 5:45 pm

The primary adjusting bolts or nuts, (depending on the model), move the gearbox forward to slacken the chain. Slacken the top gearbox bolt & rear chain first as they will hold the gearbox from shifting forward. Run the adjuster(s) up until you can replace the chain, then step on the bottom run of the rear chain to tension the front one. Now run up the adjuster(s) until the proper slack is obtained, 3/8" for most models. Retighten the top bolt & recheck slack, then adjust rear chain. This is the recommended method & reduces the chance of the rear drive shifting the 'box while driving.

Biscuit · Post by **Biscuit** » Wed May 10, 2006 6:14 pm

What I had in mind when I referred to 'fun', was that if the primary chain was that far gone, the secondary may well have been shortened.Personally in your situation, I would remove the secondary chain, get the primary right and then go on from there.

MartinL · Post by **MartinL** » Sat May 13, 2006 9:44 pm

"What I had in mind when I referred to 'fun', was that if the primary chain was that far gone, the secondary may well have been shortened"

You were right Alan.The chain had been shortened, making it impossible to move the gaerbox forward far enough to fit the new primary chain. I've fitted a new final drive chain (that too was well and truely bu99ered), and out everything back together. If it doesn't rain tomorrow I will give it a test run then.