07 125 Gearbox Problems

[weeble]

My lad was riding his 125 gasser today and clouted the gear lever on a log which turned it round on closer inspection it turned out that its not spun it on the splines but it looks as if the return spring or something has broken . Can get all the gears but the lever just goes further and further round. Has anybody else come across this,any advice, guidance would be welcome.Cheers

[jse]

My lad was riding his 125 gasser today and clouted the gear lever on a log which turned it round on closer inspection it turned out that its not spun it on the splines but it looks as if the return spring or something has broken . Can get all the gears but the lever just goes further and further round. Has anybody else come across this,any advice, guidance would be welcome.Cheers

First thing to check is the shift centering spring/carrier at the end of the shift shaft, under the clutch basket. If that is in good shape, your son may have damaged the shift shaft internally. There are two spring-loaded rollers that engage inside the shift drum and if damaged, you will need to split the cases to replace it.

Jon

[peterb]

Hello Weeble,

I agree with Jon and add the following. It's very likely to be the gear change return spring CAP at the end of the gear shaft, clutch side. The cap is pressed together and some of these can rotate out of alignment quite easily when clouting the gear lever on rocks and trees, nothing major if so. To have a look, tip the bike over to the left, remove the clutch cover, leave the coolant circuit intact, mind out not to loose the kickstart shaft washer and tap the clutch centre nut with a drift before undoing with a non-ball ended 4mm allen key. (Don't round off the allen screw). The clutch comes away as one unit if you hold it from the underneath.

Beneath the clutch is the end of the gear shaft with the cap and spring. The cap has a centre piece that should be in alignment with the spring tab. If it is out of alignment, remove the cap then you can twist back and then carefully braze the cap parts together if you are stuck for a new part, but best to buy a new cap with spring.

Bye, PeterB.

[weeble]

Thanks a lot will have a look tonight, hope its the cap.Cheers

[jse]

Hello Weeble,

I agree with Jon and add the following. It's very likely to be the gear change return spring CAP at the end of the gear shaft, clutch side. The cap is pressed together and some of these can rotate out of alignment quite easily when clouting the gear lever on rocks and trees, nothing major if so. To have a look, tip the bike over to the left, remove the clutch cover, leave the coolant circuit intact, mind out not to loose the kickstart shaft washer and tap the clutch centre nut with a drift before undoing with a non-ball ended 4mm allen key. (Don't round off the allen screw). The clutch comes away as one unit if you hold it from the underneath.

Beneath the clutch is the end of the gear shaft with the cap and spring. The cap has a centre piece that should be in alignment with the spring tab. If it is out of alignment, remove the cap then you can twist back and then carefully braze the cap parts together if you are stuck for a new part, but best to buy a new cap with spring.

Bye, PeterB.

Good description of the process. I would add that if Weeble is going to braze the end cap to the the spring bushing that it needs to be very closely aligned to the original position in order to keep the shift lever at it's original, but then again, the lever could be re-positioned. The only concern with a repair is that a "fail-safe" mechanism is lost. From what I can deduce, the end cap is, on purpose, lightly furnace-brazed on in order to seperate before damage is done to the internals, kinda like the older model, riveted shiftdrum claw arm where the rivet would snap if the lever took a big hit and just replacing the rivet would fix the problem.

Jon

[weeble]

Thanks to you both it turned out to be the cap got another one on order from gas gas uk. Would just like to know how much tension to put on the spring when i put it back together and should the allen bolt that holds the clutch basket on be fairly tight as it seemed to come off very easy. Thanks again, weeble.

[peterb]

Hi Weeble,

Good that you bought a new cap, as Jon says, it is there for a failsafe mechanism to protect the rest of the selector mechanism.

The springs have always been attached to the cap when I have worked on these, try installing with a full 360 degree twist on the spring, mind your fingers.

The clutch centre bolt should be reasonably tight, sorry, no torque figures.

Before fitting the clutch, check that all of the gears can be selected going up and down the ratios, as this is determined by the spring rest post, which looks like a sleeve with a 4mm Allen screw on top, it is drilled eccentrically to provide a small range of adjustment for the selector central resting position, to adjust, slacken the Allen screw and rotate the sleeve with a 10mm open ended spanner.

Bye, PeterB.

[jse]

Hi Weeble,

Good that you bought a new cap, as Jon says, it is there for a failsafe mechanism to protect the rest of the selector mechanism.

The springs have always been attached to the cap when I have worked on these, try installing with a full 360 degree twist on the spring, mind your fingers.

The clutch centre bolt should be reasonably tight, sorry, no torque figures.

Before fitting the clutch, check that all of the gears can be selected going up and down the ratios, as this is determined by the spring rest post, which looks like a sleeve with a 4mm Allen screw on top, it is drilled eccentrically to provide a small range of adjustment for the selector central resting position, to adjust, slacken the Allen screw and rotate the sleeve with a 10mm open ended spanner.

Bye, PeterB.

The process of centering it is a little tricky at first, so expect to make several attempts to get it right. If someone who knows how to do it shows you, it's a lot easier than describing it.

Lay the bike on it's side to take the sidecover off and you won't have to change the oil and the rear wheel will be free. Loosen the 4mm capscrew up a little but not loose. Put the shift lever down into first but do not release it (you may have to rotate the rear wheel a little to get it to go into gear). SLOWLY allow the shift lever to come back to center and just before it hits center you should hear a light "click". If you don't, adjust the eccentric bushing (10mm open-end wrench) a very small amount either way and try it again (it only takes a very small amount of turning). Repeat this if necessary till you get the click. Then try the same process with shifting up into second gear, slowly allowing the lever to return to center to make sure you get the click. If you hear the click in first (downshift) and second (upshift) the shift shaft mechanism is centered, tighten the capscrew down (7-8 ft lbs, 10-12 Nm). It will usually take a few attempts to get it right, like adjusting four-stroke valves, but once you get the hang of it, it should be a lot easier. Usually I find that once I get it centered (hear click) on the downshift, it usually is centered on the upshift, but not always.

Cheers.

Jon