Gear box shaft replacement

[NotAnotherHill]

It looks like the thread on the end of the gear box shaft has been damaged by the locknut coming loose from the front sprocket. Anybody know how big a job to is to get it replaced or whether the end can have a new thread cut in? Any idea on cost for labour etc would be useful if I have to take it to the local mechanic.

[darrsi]

Don't know how much you've read about this subject, but you're not alone.


You may want to have a look at this previous post though, and make sure you buy the newer 12mm nut, and not the original 9mm nut.


The part number is in this post:  http://foc-u.co.uk/index.php?topic=2449.0

[NotAnotherHill]

I've already replaced the nut but it is the shaft thread that I think is the problem. The threads have become rounded off so even a new nut does not secure tightly to the shaft.

[Fazerider]

So far as I know Yamaha are still doing the honourable thing and replacing the shaft FOC.
If you don't fancy having the bike off the road for ages while your local Yamaha dealer fixes it (it's a long job and they tend to leave things to one side if more profitable jobs come in), then you can weld the nut on.

[NotAnotherHill]

Wouldn't welding the nut on prevent any future sprocket and chain replacements?

[Fazerider]

Well, it's not quite as easy as before of course, but an angle grinder does the job OK.

[Raymy]

Nut came off my old bike. It wore the end of the output shaft quite a bit. I got a dremel type tool with the thinnest wheel available and steadily and carefully made an opening for the thread. If you are mega careful it is saveable. there won't be much thread but it will be enough. Or rather, should be, as long as it ain't ground too much away already tho

[NotAnotherHill]

I got the new 12mm nut and washer and took it down to the local mechanic. He thinks the thread on the gear shaft is fine. He put new one on and torqued it up. Says it shouldn't, move. Part of the problem was I hadn't levered the tabs on the washer sufficiently. A long run out tomorrow to see how it goes.

[Raymy]

The tab is near useless, ask him what he torqued it to. If he went by Haynes or an old book then it might not be enough. Old was 70 NM. Later updated to 90. Even that's no guarantee. Bit of thread lock, wedge up two sides of washer if not done so already and regular checks. It's a 5 minute job to get cover off and have a peek.
Also listen out for the jingle jangle of the loose washer when it goes. It will sound like a key rattling off a 2 bob in yer pocket constantly. Left pocket obviously