G80 CP Burman mainshaft problem

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
hatrack
Posts: 69
Joined: Thu Sep 07, 2017 3:36 pm
Location: Somerset

Re: G80 CP Burman mainshaft problem

Post by hatrack »

Interesting.
As there is no sing of any of the threaded shaft broken of in the nut., itsa real mystery.
The bike was running. As I said there was the end thread hanging loose, like a torn fingernail. A friend has suggested that the nut could have been replaced, with less than a whole thread engaged, perhaps secured with Loctite, and it finally let go.
hatrack
Posts: 69
Joined: Thu Sep 07, 2017 3:36 pm
Location: Somerset

Re: G80 CP Burman mainshaft problem

Post by hatrack »

Chris Berry wrote:I find your problem very interesting. When I purchased my 1948 G80 around 18 months ago I also bought another gearbox to go with it. After overhaul I replaced the old one with the new. when I pulled the side casing off the old gearbox I was astounded to find that the nut retaining the kick start assy onto the mainshaft had been welded on. Not just a little tack but a full peripheral weld. I have no explanation as to why someone would do this but, by the time i ground the weld off, the main shaft was next to useless. I noticed that on mine also there was not much thread on the shaft to purchase on so may be this was the reason for the weld
Oh dear Chris, you have put a very evil thought in my mind!
As this morning I burrowed through the shed to find that spare gearbox (which I did) I also dug out my welding gear which I need for something else, and as I paused for a coffee, I thought "why not?"
It seems horribly drastic, but....
Having looked inside the spare gearbox's cover, I see the mainshaft thread protruding 1/16" beyond the nut. This means that the shaft in the gearbox on the bike is well and truley buggered, with 5/16" missing from the threaded, kickstart ratchet end.
As the bike has no roof over its head, and I do not want the delay of getting gearbox and mainshaft out and back in, or swapping to an untried spare box, I will follow that unknown bodgers lead and weld the splined kickstart ratchet in place,
probably until after the Italy trip, and sort out a prioper solution after that.
zwarts
Posts: 514
Joined: Mon Jan 01, 1990 12:00 am
Location: LANCASHIRE UK

Re: G80 CP Burman mainshaft problem

Post by zwarts »

Peter, here's another solution to your gearbox problem. You have a spare gearbox, so take out the main shaft and swap it for the faulty one.
Welding the kick start ratchet onto the shaft is a bodge. The ratchet is hardened to minimise wear and the heat from welding will almost certainly soften it, then you will have other problems.
These CP main shafts are not uncommon items at autojumbles so the damaged shaft in your box will not be difficult to replace. Take the old one with you as a reliable guide to the dimensions as the BAP main shaft looks very similar but is bigger in many of it's dimensions!
Do the job once and do it right, good luck,
Bob.
hatrack
Posts: 69
Joined: Thu Sep 07, 2017 3:36 pm
Location: Somerset

Re: G80 CP Burman mainshaft problem

Post by hatrack »

I know what you mean Bob. But removing and replacing mainshaft without a garage is not a practical prospect at this time of year.
I'm not rushing into it, as the concrete base for new garage is now down and providers of the new timber double garage are coming to check it out on Monday. I'll see what they say, maybe in a weeks time I can work on it under cover.
If so I'll probably check out the spare '49 oil lubed box and fit that. It looks in excellent order inside the kick start cover and turns very freely but I haven't checked gear selection yet.
With a bench to work on, it will be easy to strip it to properly check the internals.
Are the output oil seals for those boxes available.
If the new garage is delayed, I have to get it running, to put in some miles, for myself as well as the bike, to make sure we are both fit for the trip.
I can limit the heat spread into the ratchet, and I'd rather ride witrh that bodge than let the weeks slip away and not have time to put right any other snags that may show up.
zwarts
Posts: 514
Joined: Mon Jan 01, 1990 12:00 am
Location: LANCASHIRE UK

Re: G80 CP Burman mainshaft problem

Post by zwarts »

Yes, the output seals are available. I usually buy them from a bearing supplier as they are a standard oil seal and just press into the metal housing. Some early CP boxes lacked the steel housing and used a felt seal so you will have to check your particular box. I will dig out the correct oil seal number for you.
hatrack
Posts: 69
Joined: Thu Sep 07, 2017 3:36 pm
Location: Somerset

Re: G80 CP Burman mainshaft problem

Post by hatrack »

Thanks.
zwarts
Posts: 514
Joined: Mon Jan 01, 1990 12:00 am
Location: LANCASHIRE UK

Re: G80 CP Burman mainshaft problem

Post by zwarts »

The part no. for the output shaft (sleeve gear) is W20015025. Bearing Services (now known as 'Brammer') have a network of local branches and can supply these seals . Other suppliers may be cheaper. AMCOC parts also has them listed under the old Burman part no. which is 27 - 12 - 2. This is listed as for the B52 box but also fits the CP box as the sleeve gear collar, bearing and housing are dimensionally identical.
hatrack
Posts: 69
Joined: Thu Sep 07, 2017 3:36 pm
Location: Somerset

Re: G80 CP Burman mainshaft problem

Post by hatrack »

Thanks, thats great.
hatrack
Posts: 69
Joined: Thu Sep 07, 2017 3:36 pm
Location: Somerset

Re: G80 CP Burman mainshaft problem

Post by hatrack »

It looks as if swapping the '49 shaft into the '47 box may not be an option anyway.
Looking at Draganfly's website and list of parts for the Burman CP gearbox, the mainshaft is a different part number up to '47 and from '48.
This might juast coincide with the change from grease lubed to oil lubed, but I cannot see how that would need a change to the mainshaft. Does anybody know this difference between the two years?
SPRIDDLER
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Re: G80 CP Burman mainshaft problem

Post by SPRIDDLER »

Perhaps

to stiffen up the mainshaft by shortening it as I posted earlier in this thread? The article doesn't say when this change occurred unfortunately.
SPRIDDLER wrote: whilst browsing the archive I came across this in the 'Transmission' section:
Burman mainshaft length.JPG
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