Output Shaft Fix

[Matt Behnke]

Hi,
  I have a 2001 Yamaha warrior 350. Yesterday when I was riding, the nut that holds the front sprocket came off, and after closer inspection I saw that the threads on the output shaft that holds the nut were stripped. They were stripped down to nothing. So I am wondering if I can just re tap this shaft for a slightly smaller nut, and call that good to hold the sprocket? I would much rather do this than to have to replace the entire shaft and take apart the engine. If I can do this, is there any specific thread type (coarse or fine, right hand, left hand, etc.) I should use? Or will this not work and I am best off replacing the whole shaft?

One thing I should mention is that we were able to drill through the shaft about a third of the way pretty easily, but then all of the sudden we couldn't drill no more. Could this shaft possible be hardened only at the core, so that I will the be able to rethread it for a different nut?

Thanks for the help

[Frank Angerano]

That's a tough question. This type of thing no matter what you do will ultimately fail after a while. Some people do crazy things hoping that it will hold even WELD IT ON! Don't do that! This output shaft is built and designed for lots of pressure and torque it's a case hardened steel.  If the bike is worth it then I strongly suggest changing that output shaft.

If you can't or don't think it's worth changing the shaft then I would say that you can try and re thread that shaft carefully, there is a die that's designed for retapping hardened steel.  Lots of oil and take your time. 

However keep in mind that the shaft size diameter changes now!  I would get a few different size washers, nuts and find a metric type nut and metric tap set. The more threads the better, use thread lock when installing the new nut if successful. 

Make sure the seal on the shaft is good before you put the new nut on if you get this done and maybe a new sprocket as well so you are not taking it apart again later due to a failed seal or beat up sprocket. 

Again I don't think that whatever you do will fix this for a long period of time but I feel your pain about opening up that engine. That shaft change may not also be as bad as you think, do some research and see what's involved first. Should you have no choice doing shaft swap then keep in mind you might as well change as much as you can on that puppy while it's out opened up etc! Good luck. 

 

 

[Matt Behnke]

Thank you! If rethreading doesn't work, then I suppose I have no other choice but to go into the engine. I also thought about welding a thread insert on the shaft, this way I can still get new sprockets on and off, but not sure how well that would work

[Frank Angerano]

Wasting your time with a thread inset and also super important is make sure  before welding anything that you disconnect all wires from the battery, engine plugs, stator coil etc. Yoou will do damage to the electrical components on the bike!!!!