Chain case and oil tank

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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Chain case and oil tank

Postby AJS_Chris » Tue Jan 23, 2018 1:12 pm

Afternoon all,
I'm giving my 1951 Model 18S a bit of a winter going over and decided to replace the chain case seal with one of the modified designs. I bought a new aluminium band at the same time because mine was scruffy. I decided to removed the battery carrier and footrest to gain better access for the job. The battery carrier was a bit fiddly because of the accessibility of the mounting nuts but not too bad. However I found that I couldn't actually remove the footrest from the bike, I got the nuts off OK and the square section shaft out but there wasn't enough clearance between the chain case and frame tube to actually get the footrest away from the bike - - is this normal? If I ever needed to fully remove the footrest I think I'd need to remove the complete chain case, hence primary chain, clutch etc, this can't be right, can it?
Anyway, on to the job, I fitted a thick washer to the outer chain case mounting pillar as suggested in one or two threads to allow for the thickness of the seal, however there was no way the new aluminium band was going to fit, the radius at the point where the band clamps together is all wrong and the band actually tries to dig into the seal. As a test I fitted my old band and this went on perfectly. There doesn't appear to be a huge difference between the bands when laid on top of each other. The first picture below shows the new band, the second picture the old band. You can see how the old band is much better fit at the joint.

image 1.jpg


image 2.jpg


Am I missing the obvious (again). On the face of it the band is simply too small with the incorrect radius.

On to the the oil tank. Having removed the battery carrier I can see the back of the oil tank. There are two pipes exiting the bottom of the oil tank and pointing towards the drive chain. One of the pipes is an overflow, I tested this by spraying a little WD40 down the 'highest' pipe visible with the oil tank filler cap removed. The other pipe exiting the oil tank has a piece of rubber tube fitted that is routed to a point above the drive chain, I assume (dangerously) that this is intended as a chain oiler but I can find no reference to this in the owners handbook or Pitman. If it is a chain oiler can it be adjusted or is it preset, also, how is it controlled, i.e. what turns it off? (I'm thinking about the use of vacuum with a Scott Oiler).

Once again, thank you in advance for any advice, this forum has been really helpful to a guy brought up on Japanese motorbikes.
Chris.
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Re: Chain case and oil tank

Postby Rob Harknett » Tue Jan 23, 2018 2:01 pm

Ashampoo_Snap_2018.01.23_13h51m07s_001_.png

Looks like the footrest is stuck behind the chain case. All you need to do is remove nut and washer only. Depress the brake lever, pull off the footrest. Plenty of room see picture. On the band it looks like the bottom fitting has made a smaller rad. so it digs in. Find an open ended spanner with a rad that fits the old band bottom rad. Put it in a vice to act as an anvil. Gently tap the band to open out the rad the same as the spanner rad. Perhaps shorten the tab a little so it just about meets the upper tab when fitted up tight.
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Re: Chain case and oil tank

Postby Expat » Tue Jan 23, 2018 2:49 pm

Chris, Not familiar with your bike but it sounds like the footrest is mounted inside the frame tube. Incorrect item maybe?

Steve
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Re: Chain case and oil tank

Postby JimFitz » Tue Jan 23, 2018 3:16 pm

When I fitted my "new improved seal" from club spares I found that I had to fit a longer screw on the band when fitting. Once it started tightening I dressed the band to shape with light taps from a hide mallet, then tightened a bit more, then dressed until it tightened right up.
It is important when fitting the seal to make sure that the tongue fits all the way in between the chaincase halves and then just nip up the central nut to hold the band in place before fitting the band and a final tighten on the central nut.
The new seals are a vast improvement and my G80 has not leaked a drop of oil since - well not from the chaincase anyway ;)

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: Chain case and oil tank

Postby AJS_Chris » Tue Jan 23, 2018 5:32 pm

Thanks guys,
I'll see if I can fettle the new band to open out the radius, doesn't need too much.
My Model 18 isn't standard (I should have mentioned this!), it was rebuilt by the previous owner with some CS details, please see the picture below.

IMG_2333a.jpg


Could it be that the footrests are off a CS, they appear to be designed to fit between the frame and engine, neither look like the one in the photo provided by Rob. I've just had a quick look at the parts manual and there are three different footrests listed, two of them are used solely on 'C' models. If they are designed to go between the frame and engine maybe there's more clearance on a 'proper' CS?

The next two photos show the left hand footrest in position and the right hand footrest removed from the bike. It's interesting that the left hand footrest goes over the frame tube whereas the right hand footrest goes under the frame tube. The only explanation I have for this is I don't know how you would get the footrest shaft out if both footrest went under the frame tube, you wouldn't be able to push the shaft in either direction.

LH.jpg


RH.jpg


Did anyone have an answer about the chain oiler?

Thanks again,

Chris.
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Re: Chain case and oil tank

Postby Rob Harknett » Tue Jan 23, 2018 7:46 pm

Delete chain oiler for vent pipe. Bit like the short pipe crank case breather. Some people extend these pipes, so any oil mist whatever goes to the rear chain. Leave these extended pipes off and lubricate the rear chain in the normal manner as instructed. Should oil pool in a pipe it may actually block it. Then you have no vent.

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Re: Chain case and oil tank

Postby Rob Harknett » Tue Jan 23, 2018 7:49 pm

Maybe you could swap footrests with some that has what you want and wants what you have. You may also need a footrest bar to suit. Check your parts list for any spacers, washers etc

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Re: Chain case and oil tank

Postby Group Leader » Tue Jan 23, 2018 10:13 pm

And when fitting the chaincase band I found it most useful to lubricate the inner face of the band. Without lubrication the band drags on the seal and distorts it, with lubrication it slides nicely over the seal. I believe my seal is one of the ones from the chap in Norfolk who advertises in Jampot - is the "Improved seal" from the club similar I wonder?

Alan
1953 AJS 16MS and a 1/3 scale Sopwith Triplane but that's another story ..... :lol:

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Re: Chain case and oil tank

Postby Expat » Wed Jan 24, 2018 2:06 am

Nice looking bike Chris.
Keep shiny side up.

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Re: Chain case and oil tank

Postby ajscomboman » Wed Jan 24, 2018 6:33 am

Group Leader wrote:And when fitting the chaincase band I found it most useful to lubricate the inner face of the band. Without lubrication the band drags on the seal and distorts it, with lubrication it slides nicely over the seal. I believe my seal is one of the ones from the chap in Norfolk who advertises in Jampot - is the "Improved seal" from the club similar I wonder?

Alan


Nope nothing like it.

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