Gearbox output shaft bearing

Information relating to the Matchless G2 or AJS Model 14 250cc Lightweight
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Re: Gearbox output shaft bearing

Postby Steve S » Thu Apr 20, 2017 8:58 am

My thought is that dealers have mistakenly sold the pegged third gear as the replacement to match the sleeve gear with dogs. Les at Russell motors swears blind that the one with pegs he sold me a few months agog is part number 044076, but we now have confirmation that this one should definitely have dogs.

The mismatch led to a fair amount of damage to my sleeve gear dogs and jumping out of top gear even on a light load.

Steve S.

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Re: Gearbox output shaft bearing

Postby Ozmadman » Thu Apr 20, 2017 3:50 pm

Just to open a similar can of worms... the second gear on the layshaft is the same gear as the aforementioned 3rd/sliding gear. This was never modded and remains the peg type BUT this still matches up with a dogged 1st gear as far as I remember??? or is that 1st/kick start gear recessed to take the pegs? can't remember now
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1960 Model 8
1974 Yamaha RD250B US Model 6 speed

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Re: Gearbox output shaft bearing

Postby clanger9 » Thu Apr 20, 2017 4:22 pm

Definite can of worms. Pegs, dogs, take your pick! ;)

Here are photos of two 1st/2nd gear sets I have to hand. I can't say for definite if these are "early" or "late" - the serial numbers of the gearboxes these were taken from are G3053 for the left pair and G4854 for the right (but as we know these gearboxes could have been fitted with anything over the years)
IMG_1038.jpg


IMG_1039.jpg

The gearbox fitted to my CSR is much later than either of these (GR21322), so no doubt when I take it to bits I'll find something different again...
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1966 AJS Model 14 250 CSR "cafe racer"
1993 Ducati 750SS

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Re: Gearbox output shaft bearing

Postby Ozmadman » Thu Apr 20, 2017 10:50 pm

clanger9 wrote:Definite can of worms. Pegs, dogs, take your pick! ;)

Here are photos of two 1st/2nd gear sets I have to hand. I can't say for definite if these are "early" or "late" - the serial numbers of the gearboxes these were taken from are G3053 for the left pair and G4854 for the right (but as we know these gearboxes could have been fitted with anything over the years)
The gearbox fitted to my CSR is much later than either of these (GR21322), so no doubt when I take it to bits I'll find something different again...
Thanks, that has answered my question (the 1st gear has recesses to take the pins/dogs) and I reckon from that picture both would work fine. Those box numbers of yours should both be the late type as far as I can tell
Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed

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Re: Gearbox output shaft bearing

Postby Steve S » Fri Apr 21, 2017 9:43 am

Ozmadman wrote:Just to open a similar can of worms... the second gear on the layshaft is the same gear as the aforementioned 3rd/sliding gear. This was never modded and remains the peg type BUT this still matches up with a dogged 1st gear as far as I remember??? or is that 1st/kick start gear recessed to take the pegs? can't remember now


Yes the kick start gear has recesses for the pegs, just checked my box in bits, Steve S.

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Re: Gearbox output shaft bearing

Postby Steve S » Tue May 23, 2017 9:10 am

Well I'm now able to re-assemble the Model 8 gearbox after successfully finding a new output gear (Norvil) and the correct sliding gear 044076 with undercut dogs from Andrew Engineering that Paul and I stumbled upon.

Paul had recently very helpfully confirmed the position of the output oil seal to be 4.5 mm into the casing so that is now correct.

I put the cluster in without a gasket (using Paul's brilliant method) and confirmed it all selected correctly. I then re-started the assembly by tightening the sprocket nut on the output gear (with the new 20 tooth sprocket) but discovered an unacceptable amount of end float (estimated at a quarter of a mm). I therefore tried fitting the odd looking brass spacer (see photo) that I had found on disassembly but this made only a slight difference. The sprocket doesn't feel secure but rocks in and out and side to side slightly. I hadn't tightened it up much as I intend to do this when its on the bike with the chain to hold it.

I put the original output gear back in (and also with the old 19 tooth sprocket) and the result is the same.

Do I need to fully tighten this nut to take up the end float?

My output gear appears to be in good condition but could this be the culprit?

Is it possible I have an incorrect length spacer?

Any suggestions would be most welcome as I really ought to be riding the bike by now!

Steve S.
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Re: Gearbox output shaft bearing

Postby clanger9 » Tue May 23, 2017 11:24 am

Isn't it meant to move? I think the workshop manual describes the output shaft bearing as "self aligning", which presumably requires a small amount of endfloat...
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Re: Gearbox output shaft bearing

Postby Janet » Tue May 23, 2017 12:12 pm

Steve S wrote: I therefore tried fitting the odd looking brass spacer (see photo) that I had found on disassembly but this made only a slight difference.
I don't think I've got one of those.
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Re: Gearbox output shaft bearing

Postby Ozmadman » Tue May 23, 2017 3:41 pm

You don't need that brass ring thing, it's not a standard part, there is no spacer there just the one which the oil seal runs on. I would only tighten that large nut last after the rest of the box has been put together but it does nothing for the end float, it just holds the sprocket on. Have you tightened the nut fully on the other end of the main shaft (where that small bearing is ??) if that is loose you will have excessive end float. You shouldn't have much end float but just checked my spare box and there is a fraction there (half a mm doesn't sound too much TBH) As for the side to side movement, my spare box has none and as you have replaced both brass bushes in the sleeve gear (so no play between the bushes and the main shaft) and the sleeve gear large bearing?? I can't see why you have movement. Check that nut on the other end on the mains haft first and get back. PS... If you clamp the sprocket in a vice (or as I do in the jaws of my Black and decker workmate, with some extra wood) with the box hanging underneath you can tighten up the sprocket before you put it back on the bike
Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed

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Re: Gearbox output shaft bearing

Postby Steve S » Tue May 23, 2017 4:05 pm

Thanks Clanger and Paul, I've checked the workshop manual and as Clanger says on page 52 the sleeve (main) gear will waggle about unless supported by the mainshaft. I noticed all this when I took the mainshaft and gear clusters out so I think all is as it should be when I put them back in and I'm grateful for Paul's comment about end float being normal.

I tightened the small end of the mainshaft nut with the shaft secured in wooden blocks in a Workmate and also used Loctite on it.

I'll ditch the brass ring as well although it does make me wonder why it was there at all; mind you when I took the box apart there was no gasket for the inner casing and other bodges that suggest someone didn't know what they were doing!

My new 124 link chain and clutch cable arrived today and so there's not much left to hold me up!

Steve S.

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