The shaft thread is well and truely stripped.



It's possible that I somehow stripped it, but I don't understand how I could have. I turned the nut the correct way the entire time, I unstaked the nut before undoing it. It just does not make sense.

The thread inside the nut is fine.

The only way I see this possibly happening is that it was stripped in the past and rattle gunned back on, or the nut was put on cross threaded and then rattle gunned on.

You could try cutting a new thread if you do not want to replace the shaft, you have nothing to loose I guess. Measure the outside diameter of the stripped thread and the pitch of the original thread. Check that you can get a nut to suit the measured diameter and pitch. If you can find a nut, then you need to find a die or a die nut the same size and pitch as the new nut and away you go. A die nut may be easier to use in the confined space. Again the shaft material might be quite hard and a die might not be able to cut a thread.

Yep that's exactly what I was thinking. It's hardened steel, tungsten steel should cut it. I would also have to Loctite the nut, which would require a butane torch to get it off next time. Shitty situation though, don't have the time, space or money for this.

I only have the pictures from my haynes manual to go by, but if you leave the lock washer off and reverse the clutch nut, is there enough original thread on the input shaft to screw the nut onto.

I don't think it's such a good idea. Without the washer, the force won't be distributed evenly and will cause the thread to fail again, over time.

I showed it to my mechanic mate, and he said it looks as though the last person to tighten the nut, over-torqued it, which damaged the thread, and over time with the force from the clutch on it, caused the threads to fail and it was stripped.

That would explain why it failed in such a short space of time and why it was slipping and not able to full engage. I also believe that theory because when the nut was on the clutch and I hadn't touched it, I could move the entire clutch basket back and forwards about a mm, which I thought was abnormal.

So in the end, I've decided I'm going to pull the engine out of the bike, bring it around to his shop, and we are going to pull the sump off, split the crank case and change the input shaft for another one.

I have a question about that, the Haynes manual says I need to remove the entire cylinder head just to get to the transmission shaft, that seems a bit ridiculous, considering the input shaft is in the bottom of the engine. Shouldn't I only have to turn the engine upside down and remove the sump and split the crank case? Then the transmission shafts can be pulled straight out from there...

It talks about removing the rear cylinder head if the transmission shafts are to be removed because one of the case bolts will not be accessible with a torque wrench when it comes time to put it all back together. I would probably rely on my arm as a torque wrench and leave the rear head in place.

Haha yeah that's what I'm thinking. But if it can be tightened with a wrench, I don't understand how a torque wrench can't do it? Can't you chuck a universal link or an extension bar or whatever on it, in order to reach it..

I think the problem might be that some part of the head sits close over the top of the bolt and a socket and torque wrench would be too tall. A flat ring spanner should work but as I have not actually seen the problem I am only guessing.

It'd be the last time you ever removed the clutch, but could you tighten it up enough to weld the nut on?

I would not be going near the clutch with a welder, to be completely honest. Heating the metal to hundreds of degrees, the diaphragm springs would distort, shit would get crazy.

It's a good bike, I want it all in good condition for when I sell it. I'm not going to do a bodgy job like the last bloke did. But I'll be finding him and finding out how the fuck it happened.