Worn spline on the gearbox output shaft

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G'day all,

Have any of you good folks ever had a really worn spline on the gearbox output shaft, and what did you do about it (short of replacing the shaft)?

The reason I ask is because my bike has a degree of what you might call 'rotational freeplay' of the drive sprocket, where it mounts on the shaft. This leads to the sprocket moving forward and backward on the shaft, as you alternate between engine braking and then powering off again (hope that makes some sort of sense).

I have tried locktite, but this does not help. I have made sure the sprocket nut is done up nice and tight, but this only does the trick for a short time; before too long the freeplay has returned and so the sprocket moves back and forth with an audible 'clack' sound whenever you put the power in to move off.

I am now thinking of inserting small slivers of steel into the free space between the spline and the sprocket's 'teeth' where they meet the spline.

What would you do -- short of replacing the whole darn shaft?

All advice welcome.

Mike.

[Jethro]

What would you do -- short of replacing the whole darn shaft?

Unfortunately, this is probably the only right way to solve the problem. Imagine the force that is on the output shaft- that is, all of it. Every foot lb of torque is transfered through there, and nothing else will be a long term fix.

I do, however, pride myself as being a resourceful type. If I were faced with this problem and I had to micky mouse something, I guess I would try and alter the sprocket itself. Maybe by taking a torch to the sprocket splines and trying to mash them a little wider by using a tapered bar of some sort. Or possibly spot welding the tightend nut to the sprocket itself. Would make a dremel tool nessecary upon removal of the sprocket, but it would do the trick. Maybe.

[RacingJake]

Are you sure it's not the sprocket, maybe a wrong one? Can you see the worn spot on the shaft ? I'd try a new sprocket and lock washer first before removing the shaft.

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Unfortunately, this is probably the only right way to solve the problem.

Thanks Jethro for helping me come to terms with the only proper solution! Most of competent motorcycle maintenance is psychology. I mean, naturally the lazy human in me is reluctant to lift out an engine, split the cases, and replace the shaft with an item that will probably cost me mega-$, when there really is nothing else wrong with it apart from slipping out of 2nd gear once in a while... but you are right, sometimes the long road is the best road. So thankyou for the mental fortification.

RacingJake: yes, I thought it could be sprocket teeth too, so I waited until installing a new set of chain and sprockets (2 weeks ago) to be sure, but alas, there was no improvement.

And yes, the wear is indeed visible on the shaft. I think someone must have been flogging around with a loose sprocket nut for a while to do this sort of damage.

Anyway, while I'm on the lookout for a shaft (or might as well get another engine while I'm at it), I think I will try inserting slivers of steel into the narrow gaps on the 'less-loaded' (ie. non-driven) side of the spline grooves, and see how this fares. Oh the joys of classic motorcycle ownership...

Cheers,
Mike.

[Jethro]

I think I will try inserting slivers of steel into the narrow gaps on the 'less-loaded'

Worth a shot while you're waiting to fix it for good, but remember, steel is a super malliable material, the only thing that gives it strength is more steel. Packing the non-loaded sides of the splines is definitely your best bet.

[SqDancerLynn1]

Maybe try small strips of feeler gauge stock Or?? drill small holes & break the drill off in the hole

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OK, I've done it. I used some 0.5mm gauge tin cut into strips about 1.5mm wide and 21mm long, with a 2mm long bend on the end to stop them feeding through. They *just* squeezed into the gaps (non-loaded sides of the splines), so things are now nice and tight. But imagine that, 0.5 mm of wear off the spline! 8O Anyway, I'll keep you all posted on how it holds up -- hopefully for the life of the chain & sprockets at least. And in the mean time I can be in a non-hurried hunt for another output shaft.

Cheers,
Mike.