g2 250cc gearbox

[keithm]

hi . have rebuilt my bike from a basket case.spent many hours and monny.but the problem is the gear box 2nd and 3rd gears keep jumping out .spent more monny and new brass bushes spent more time but keeps jumping out of gear not many pictures for the light weight 250cc.any help thanks

[wilko]

Worn selector forks?

[56G80S]

It's a very long time ago that I had one of these apart and I've forgotten if they have the same arrangement as the standard AMC box, but with all the internals set higher up.

If that is the case it's always worth looking at the detent spring length and strength and the "bullet shaped" detent itself. If that's too rounded at the point (although it shouldn't be sharp) then jumping out of gear can result.

Johnny B

[Tolly]

I had the same problem on my G5 a few years ago, the problem was too much end float so I used a spacer. You can measure the end float by putting a straight edge across the case, where the end cover bolts on, and with the gears in the box you can then measure the end float. You only need between 10 and 20 thou but you will probably have near one eighth of an inch.

[jajo57]

And to add to what 56G80S has said, take a close look at the gear selector shaft. If there's a marked wear line between the locating holes (where the detent plunger locates) it's likely that the holes are worn too, this will cause it to jump out of gear. This is usually a sign that the gearbox has been run with insufficient oil.

Richard

[borrop01]

Hi am rebuilding gearbox Find the shock absorber centre is too small spline to fit mainshaft. Looks like centre has been bored and a different centre pressed in.Will I have to make one to fit or are members with spare centres to swop/purchase. Club has told me no spares available. Thanks Peter.

[wilko]

show us a pic?

[borrop01]

Pic sent as requested