Lightweight Gearbox

Information relating to the Matchless G2 or AJS Model 14 250cc Lightweight
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shifter
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Lightweight Gearbox

Post by shifter »

I thought the lightweight 250 and 350 gearbox was interchangeable and could be used on either bikes i have been informed that the output shaft has to be changed in some aplications. i have tinkered with these a few times and never had to do that can anyone shed a little light on the matter Thank you
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Tolly
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Re: Lightweight Gearbox

Post by Tolly »

The main shaft is longer on the 350 because it has a duplex chain. Be careful as there are 3 different main shafts, as far as I can remember one for the 250 and an early and later for the 350. Hope this helps.
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ajscomboman
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Re: Lightweight Gearbox

Post by ajscomboman »

4 mainshafts, 2 for the 250 and 2 for the 350, 2 clutch centres to suit either the later or the earlier shaft. Wonderful these little Lightweights aren't they! Lack of spares is also a problem but the parts service have had both types of clutch centre made as these tend to wear quicker than anything else.
shifter
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Re: Lightweight Gearbox

Post by shifter »

Thank you when i have been tinkering on with these i must have hit lucky with the second hand parts i have used mind i have only done the 250 s again thanks to all for the help and advice
Mmm Could a 350 box be used on a 250 if the front cog is changed and a duplex chain used ?
Last edited by shifter on Tue Jan 31, 2017 6:59 am, edited 1 time in total.
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Ozmadman
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Re: Lightweight Gearbox

Post by Ozmadman »

Mainshaft differences
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Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed
Rangy65
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Re: Lightweight Gearbox

Post by Rangy65 »

Hello there another problem you will encounter is that 250 & 350 primary cases are different. The alternator for the 350 sits deeper inside the housing as the additional duplex drive adds width.

Don't mix yer lightweights!!

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clanger9
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Re: Lightweight Gearbox

Post by clanger9 »

...and don't forget that late-model 250CSRs also have a duplex drive. Just in case it wasn't confusing enough :)
1989 Moto Morini Dart 350
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shifter
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Re: Lightweight Gearbox

Post by shifter »

I have a 59 model 14 that I have had sitting for a long time as I am now retired I have been able to spent time on the bike. why I asked the question of gearbox fitment is the one on the bike when I have had a good inspection is going to cost £s as its not healthy at all and I have the option of a 350 box at a very good price. Clanger my daughter has a 1965 G2 that she bought last year that needed a few issues sorted I have done these and is spot on now. Now I need to get the A.J.S on the road so we can have some country lane runs a pal has just informed me he has a 250 box that has been sitting around in his old mans shed for years and I can have it for a Cpl of pints so happy days lets hope .
Thanks All
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Ozmadman
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Re: Lightweight Gearbox

Post by Ozmadman »

shifter wrote:Thank you when i have been tinkering on with these i must have hit lucky with the second hand parts i have used mind i have only done the 250 s again thanks to all for the help and advice
Mmm Could a 350 box be used on a 250 if the front cog is changed and a duplex chain used ?
Yes, internally both boxes are the same apart from mods to the mainshaft as shown above( to do with 2 different clutch centres and the differences in length between the 250(simplex) and 250/350 duplex) If you have the parts including the 350 clutch(duplex chain and one extra plate)then there will be no problem. As long as the clutch fits on the centre ok then all should be well. Whatever you use, if you intend to keep the bike then I would get the 350 box as well as parts are difficult to get. You never know with all this interchangability, I have a spare box marked with a G number which by all accounts should be a G2 box but it has the same mainshaft as my 350 which is a bonus so you never know really what you have until you check it out
Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed
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