Leaking primary cases!

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
Moto742
Posts: 6
Joined: Wed Nov 28, 2012 5:45 pm
Location: Los Angeles

Leaking primary cases!

Post by Moto742 »

So I have a well used g80 and I was wondering if anyone has the solution on stopping the oil from gushing out? I know these things leak a bit but because the early 50's models only have one bolt in the middle it tends to splay out the far edges of either side of the case. Does the spares have new UN dented ones? Or shall I just make sure mine aren't miss shapen and deal with it?
Also does the spares have the original style brass/copper oil lines? Or is there good repro ones?

Thanks I'm just a newbie
User avatar
Rob Harknett
Member
Posts: 11236
Joined: Mon Jan 01, 1990 12:00 am
Location: ESSEX UK

Re: Leaking primary cases!

Post by Rob Harknett »

Covered many times here search " chaincase etc " for all the answers.
In short, if your cases splay out you may have the wrong inner spacers.
Thats how they get pulled in at the middle. If you have pulled yours in try tapping the outter half out again.
You will note various methods of sealing the cases inc. a new type rubber.
User avatar
tr7dan
Posts: 146
Joined: Tue May 11, 2010 11:49 pm
Location: LANCS UK

Re: Leaking primary cases!

Post by tr7dan »

Hi Rick

of all the questions that get asked on here, apart from 'which is the best oil....' the leaky chaincase question is probably the most contentious.

There are loads of posts on here about solving the problem, just have a search through, and people have their own ways of dealing with it so you can read through and take your pick.

Personally, I use plumbers silicone, I find it quick, easy and it works 100% every time for me.... but then, i's something I use every day of my working life so I am expert in its application.

Good luck

Dan
Moto742
Posts: 6
Joined: Wed Nov 28, 2012 5:45 pm
Location: Los Angeles

Re: Leaking primary cases!

Post by Moto742 »

Yeah I see there is over 200 post concerning chaincases! Hey Rob the info on the spacers seems to be the ticket. How bout the question about oil lines? Thanks fellows
en7jos
Posts: 1063
Joined: Wed Oct 13, 2010 12:00 pm
Location: Hong Kong
Contact:

Re: Leaking primary cases!

Post by en7jos »

After not having been out on my G3 for a good few months (actually not since last year sadly) I uncovered it on Friday to put the battery on charge, and of course to drain the sump. Drained 600ml of oil from the sump, and another 700ml from the primary!!! Bad news: it wet sumps. Good news: primary is oil tight at last. :)

Seems the (straighten it + smooth edges + space it) x repeat 20 times then + Buckingham seal + new ally tightening band approach eventually worked for me!

Crankcase leaks also eventually traced to bolts made from toffee (not) holding engine together in frame, so replacing with some more structural pieces that could actually be tightened did the trick.

Think it's about as oil tight as I can ever wish for now :)

James
----------------------------------------------------------------------
My Matchless G3LS website is here - http://www.matchlessclueless.com
----------------------------------------------------------------------
Matchless_Mayhem
Posts: 124
Joined: Thu Oct 11, 2012 11:48 am
Location: MONMOUTHSHIRE UK

Re: Leaking primary cases!

Post by Matchless_Mayhem »

The inner spacer arrangement (primary chaincase) on my G9 was completely mismatched, splaying/distorting the outer case - easily remedied with the addition of some machined aluminum bar, and the chaincase seal itself had been 'finished' with the application of some electrical tape - again easily remedied by fitting the 'Buckingham Neoprene Seal' - best £10 I've spent - see ad section of Jampot Magazine.
Who, me!?
User avatar
clive
Member
Posts: 5657
Joined: Mon Jan 01, 1990 12:00 am
Location: LONDON UK

Re: Leaking primary cases!

Post by clive »

Learn to live with a little oil leak, at least you only have to check the oil when It does not leave its calling card on the road when parked up. Would agree however that the trick is to get internal spacers right. you should be able to get a long threaded nut to act as internal spacer, but you may still need to add washers behind so the cover has about 1/8 to 1/4 inch gap all round without the rubber in place. Then fit the Buckingham seal. Will probably then only leak from the gearbox entry hole! And the oil breather will still probably drip too. I see it as an ecologically sound way to dispose of the oil, simply spread it around your local roads rather than pouring it down the drain. (no I don't do that, any more)
clive
if it ain't broke don't fix
Trefor
Member
Posts: 228
Joined: Fri Dec 31, 2010 10:02 am
Location: South Australia AUSTRALIA

Re: Leaking primary cases!

Post by Trefor »

I found sealing the primary case relatively easy using rubber tube (without sealant), but the oil is thrown out of the large hole on the inside of the casing behind the clutch which makes it look like the case seal is leaking. I don't know if there is a solution for that.
User avatar
Taid
Posts: 710
Joined: Mon Oct 07, 2019 3:35 pm
Location: Shropshire UK

Re: Leaking primary cases!

Post by Taid »

clive wrote: ............................................ Would agree however that the trick is to get internal spacers right. you should be able to get a long threaded nut to act as internal spacer, but you may still need to add washers behind so the cover has about 1/8 to 1/4 inch gap all round without the rubber in place. Then fit the Buckingham seal. Will probably then only leak from the gearbox entry hole! And the oil breather will still probably drip too. I see it as an ecologically sound way to dispose of the oil, simply spread it around your local roads rather than pouring it down the drain. (no I don't do that, any more)
Out of context, in that my machine is a 16MS , but I think that it is the same casing ..

Having replaced the outer casing a few days ago (without reading the forum), and using the existing neoprene (or whatever) band, oil leaked almost before I had finished topping up ..

So, after reading the forum, I have purchased a new (updated) seal. I have no gap around the chaincase, nor do I see any sign of a spacer .. the retaining stud appears to be made from a hex bar about 5/8" a/f, but I can't find any illustration in the parts list, so I have no idea what to expect.

When I took it apart, the bottom gap had been sealed with silicon sealant, presumably by putting an oversize bead along the bottom edge of the inner and outer and then assembling before it had gone off.

All advice on reassembly appreciated ..
___

Now sold ... 1956 AJS 16MS Bitsa .. HSU 414 .. rebuilt/re-registered 1987
User avatar
dave16mct
Member
Posts: 3234
Joined: Mon Jan 01, 1990 12:00 am
Location: LANCASHIRE UK

Re: Leaking primary cases!

Post by dave16mct »

That hexagonal bar is the spacer/nut. You will need to add a washer or 2 to make room for the new seal to fit. It will be about an inch too long so cut it to length and put the joint at the top. Glue the ends if you like, I don't bother. Assemble carefully and most important, don't put too much oil in. It only needs just enough to barely touch the bottom of the chain.
Dave.
Locked