Breather and Chaincase Seal 54 18S

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
g4321
Posts: 19
Joined: Wed Feb 06, 2002 12:00 am
Location: MORAY UK

Breather and Chaincase Seal 54 18S

Post by g4321 »

I have a 1954 Model 18S and I have a couple of questions for some similar owners.

On my bike there is no seal between the gearbox and the tin chaincase, the result is even with a fairly low level of oil in the chain case a reasonable quantity of oil is always transfered to the final drive chain and coats the outside (back/engine side) of the chaincase. Is there any seal fitted on any single - in addition water is always transferred from the same source into the chaincase oil.
I have spent ages getting the engine 95% oil tight (to minimise ribbing from my modern bike riding mates) with only a few minor weeps but would like to get rid of or minimise the oil drips that appear to come from the back of the tin chaincase after a long run. I have a good seal on the chaincase band and am pretty sure that it is as oil tight as it ever will be!

The second question is regarding the breather - I have fitted a pipe onto the crankcase breather to route it away from the back of the chaincase and into a 'catch bottle' (which is vented). Does anyone see a problem with this arrangement or has anyone ever tried a similar arangement - the pipe routing does go slightly upwards to enter the catch bottle.


User avatar
paul knapp
Posts: 1645
Joined: Wed Oct 12, 2005 10:45 pm
Location: SOUTH AUSTRALIA AUSTRALIA

Breather and Chaincase Seal 54 18S

Post by paul knapp »

Your "fairly low" oil level may be to high! When bike is vertical, the chain should just skim across the oil surface, at its slackest point. You have not got gearbox oil coming out have you? What is the source the water comes from in such a quantity that it enters the case?
The breather sounds good to me, any thing to keep the oil in and dust out.
Regards,.. P.K.

___“As a hobby for the technically minded, motorcycling provides great scope.”

J.B.Nicholson

Don't worry about the world coming to an end today. It's already tomorrow in Australia!


_____________________________________________



g4321
Posts: 19
Joined: Wed Feb 06, 2002 12:00 am
Location: MORAY UK

Breather and Chaincase Seal 54 18S

Post by g4321 »

My wording about the chaincase is a bit missleading. Please see ammended copy below.

On my bike there is no seal between the final drive chain and the tin chaincase, the result is even with a fairly low level of oil in the chain case a reasonable quantity of oil is always transfered to the final drive chain and coats the outside (back/engine side) of the chaincase. Is there any seal fitted on any single - in addition water is always transferred from the same source into the chaincase oil - when washing the bike for example.
I would like to get rid of or minimise the oil drips that appear to come from the back of the tin chaincase after a long run. I have a good seal on the chaincase band and am pretty sure that it is as oil tight as it ever will be
User avatar
Biscuit
Deceased
Posts: 3924
Joined: Thu Jan 01, 1998 12:00 am
Location: KENT UK

Breather and Chaincase Seal 54 18S

Post by Biscuit »

Some bikes are fitted with a sliding portion, the bore of which fits closely around the output shaft. I'm not sure whether this feature is year or model related, but it is fitted to AMC boxes only, thus would not suit your model. There should be an (inefficient) deflector plate surrounding the hole for the gearbox shaft. What ever level you mantain the oil. the primary chain needs to create enough oil mist to lubricate the dynamo chain and the shock absorber cam. There is bound to be oil appearing out of the rear by the gearbox. Some members in our section have cut down the oil loss by using automatic tranmission fluid. Finally the original recommendation for the oil level is a minimum of 1/8" below the filler orifice - stick to it!. A further thought, if the oil is getting on to the secondary chain then I would suggest that the clearance between chain and rear of chaincase is insufficient.



Charles
Member
Posts: 206
Joined: Fri Jan 01, 1999 12:00 am
Location: BERKSHIRE UK

Breather and Chaincase Seal 54 18S

Post by Charles »

I have also heard of a seal being made by cleaning the inner side of the chaincase thoroughly and fitting a leather ring using appropriate glue. Apparently this stops most of the oil egress and being lether, allows for a little adjustment of the primary chain. i have not tried this myself.

regards
Charles
itma
Posts: 7721
Joined: Tue Nov 22, 2005 6:01 pm
Location: UK

Breather and Chaincase Seal 54 18S

Post by itma »

there used to be an AMC fitting on the comp., bikes that was a shallow dished plate about 4/5 inches diameter, and which carried a felt washer of the same size that rubbed on the rear of the case and made a nice tight fit and kept water etc out as well as oil in, as I recall it was held in place by the sprocket nut, but I can`t recall if it was specific to the B52 box or the CP. Have not seen one about for yonks, Russells had some in the dim past.
A pain to fit as on the CP you have to remove the mainshaft to fit it under the sprocket nut, fair bit of resistance from the felt till it was used a bit.

Paul, only an aussie would ask where does the water come from? visit us and see, from the sky mate, the sky[:(]
g4321
Posts: 19
Joined: Wed Feb 06, 2002 12:00 am
Location: MORAY UK

Breather and Chaincase Seal 54 18S

Post by g4321 »

After weekend with bike cleaned off and fresh oil in chaincase I came to conclusion oil leak may well be due to leak from chaincase seal.
This I suspect is due to distortion in the alloy band so have bit the bullet and ordered another one.
This coupled with silicone, a 'leak proof seal' and loads of crossed fingures might give me the anwer I am looking for. Then again - I may be wron and my quest for an oil tight 500 is going to be a figment of my imagination!

Thanks for all the suggestions & I might have a look at making up a sliding seal for mainshaft/chaincase back. If anyone has any tips for refitting chaincase band please reply.
User avatar
Colin F
Member
Posts: 936
Joined: Mon Jan 01, 1990 12:00 am
Location: NORWICH UK
Contact:

Breather and Chaincase Seal 54 18S

Post by Colin F »

I was given a tip many years ago which I used on a bike at the time with good results.

Very carefully clean the outside edges of the chaincase, finishing with a solvent, I think I either used meths or petrol and ensure that at least an inch each side of where the band locates is clean, grease free and dry.

Get some 3/4" or 1" insulation tape. wrap one length carefully round the inner case edge and one length round the outer case edge. Refit the case and wrap another length overlapping the previous two. half on each. Then refit the rubber seal and alloy band.

If you have fitted the tape carefully this should seal the cases and the rubber seal should help to keep the tape in place.

I seem to remember that this worked well and stopped leaks along the chaincase joint.

If you do try this method, please post your results and observations on here as it is some time since I used this method, and memory does play tricks!! [:0]
Jackson
Posts: 48
Joined: Mon Jan 01, 1996 12:00 am
Location: ENGLAND UK

Breather and Chaincase Seal 54 18S

Post by Jackson »

On the breather ; after a rebore I fitted an extension to the breather into a small vented plastic bottle slung under the engine. It worked well, but was not needed after a few hundred miles when oil loss was negligable. One of the manuals does make a comment about breathers being directed upwards to lubricate the secondary chain, but says it may cause problems increasing crankcase pressure and encouraging fumes & condensate into primary chaincase via the drive shaft main bearing that does not have a seal.

Getting into a controversial area, I seal the tin chaincase halves by applying a bead of silicon to both sealing faces them bolting them up. Leave to cure and the outer rubber etc. is redundant! The joint can be separated using a razor blade, and remade by cleaning the remaining silicon with meths, add a bit more silicon and bolt up again!

With my super sealed tin joint I also had an annoying leak, but from the dynamo shaft aperture! There was no feature on the inside of the inner chaincase half to deflect oil away from the hole. I resolved it by finding a length of plastic tube (probably 3/8"dia) the same length as the circumference of the hole. I then cut long the length twice to remove 1/4 of the cicumference of the tube. Next fit the tube around the inside of the hole (this can be done in situ with patience!) put the joint at the bottom.
What you then end up with is a 'gutter' feature ---) (--- on the inside (& outside!) that directs the oil down round the hole back into the bottom of the chaincase. (Is this the first attempt at graphics in these items??)

User avatar
Chazzyb
Member
Posts: 553
Joined: Tue Apr 08, 2003 1:00 am
Location: Suffolk UK

Breather and Chaincase Seal 54 18S

Post by Chazzyb »

Gordon, I concur with an earlier poster: too higher level in the primary causes it to evacuate - just enough to ensure the bottom run is just dipping into it seems to work for me. Also like you, I can find a lovely mayonnaise in the chain case following a run after washing the bike - careful where you push that hose! I have a 500ml syringe from Machine Mart which I use to suck it all out again.

Charles
Locked