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Stripped countershaft threads

sckego

doesn't like crashing
Joined
Jan 28, 2011
Location
San Jose
Moto(s)
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Name
Kegan
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AMA #3283468
A while ago a realized my countershaft nut was rattling around loosely, being held in place only by the lockwasher with the fold-down tabs that keep it from rotating. A bit on poking around revealed that the threads on the inner portion of the countershaft were stripped... that is, the splines that hold the sprocket and lockwasher are fine, and the threads at the outer end of the countershaft are fine (so the nut begins to thread on normally), but when the nut gets far enough down the shaft to contact the sprocket/washer, it won't reach torque--it just spins.

I'm not sure how long I was riding around like that, but the the lockwasher certainly did it's job: the nut couldn't slide off the shaft because the end was still threaded, and it couldn't spin off because the lockwasher prevented it from rotating.

I've finally gotten around to ordering and installing a new chain and sprocket set, so how do I secure the countershaft nut? I guess the simplest option would just be to bend down the lockwasher again and count on it to keep the nut on, but I'd prefer something a bit more robust. Clean off the shaft and stick the nut on there with red Loctite? Tack weld the nut to the shaft? Some other mechanical method of holding the nut in place? Hm, just thought of this--not sure if there are enough threads on there to get *another* nut on top of the existing one...

Open to other suggestions as well. Note that this is a 8-year old bike with 63k, so I'm not really open to the idea of splitting the cases to replace the countershaft...
 
If it were me, maybe another washer or 2 to add some space keeping the nut on the area that still has good threads. Either that or tack weld but be sparing with the weld material and the lock washer.

Otherwise, I'd probably replace the engine with a good used one before doing a full tear down to replace the shaft.
 
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'Best way is to add a couple precision flat washers to put the lock nut squarely in some good threads. Do NOT use inexpensive stamped washers. You want washers where the two sides are exactly parallel. The easiest way is to order more of the stock washers.

I wouldn't weld it.

And, of course, you know the proper way is to open the case and replace the shaft.

And you need to ask why the threads stripped to begin with. Did someone put the nut on with an impact wrench or breaker bar?
 
More washers plus a self locking replacement nut as the lock washer tabs might not have enough engagement at the new height. Don't use a nylock, look for deformed thread nuts. Locktite won't hurt in top of all that.

I might throw a tack weld on, but that's cuz I have the ability to and a weld cools faster than glue sets
 
if you have to do the tack weld, ( you won't be the first one to do it) as mentioned go easy on the weld. you don't want to fry your seal. just enough. you can Dremel off the weld should you have to fit a new sprocket in the future.
and be sure to disconnect your battery so you don't fry your ECU.
 
Nobody is asking why the threads failed. This is important because you don't want it to happen again. Maybe, just maybe, the shaft is defective somehow- not heat treated properly, for example. If the proper sprocket was installed properly and the proper nut was torqued properly, it shouldn't have loosened up and/or taken out those threads. Adding washers to space the nut outwards has a downside. On some bikes, the countershaft sprocket nut lives very close to the sprocket cover. Spacing it out can cause interference and grinding. Some bikes also use the countershaft sprocket nut to drive the speedo pickup coil that sends a signal to the dashboard. If the inner threads failed, what will stop the outer threads from failing the same way... if there are even enough threads to use without causing any other problems?

The shaft and the nut are not the same grade of material. Welding it can be problematic because dissimilar metals might not bond together well. The weld would only be as strong as the weaker metal, which would be the nut. Even if it could be done, it is subject to heat and vibration, either of which can cause failure. Then you have the ever present doubt of whether it's holding together or not. It becomes the same exact problem again when it's time to replace the sprocket next time around.
 
Nobody is asking why the threads failed. This is important because you don't want it to happen again. Maybe, just maybe, the shaft is defective somehow- not heat treated properly, for example. If the proper sprocket was installed properly and the proper nut was torqued properly, it shouldn't have loosened up and/or taken out those threads. Adding washers to space the nut outwards has a downside. On some bikes, the countershaft sprocket nut lives very close to the sprocket cover. Spacing it out can cause interference and grinding. Some bikes also use the countershaft sprocket nut to drive the speedo pickup coil that sends a signal to the dashboard. If the inner threads failed, what will stop the outer threads from failing the same way... if there are even enough threads to use without causing any other problems?

The shaft and the nut are not the same grade of material. Welding it can be problematic because dissimilar metals might not bond together well. The weld would only be as strong as the weaker metal, which would be the nut. Even if it could be done, it is subject to heat and vibration, either of which can cause failure. Then you have the ever present doubt of whether it's holding together or not. It becomes the same exact problem again when it's time to replace the sprocket next time around.

We already know why they failed. Obama. Right?
 
I can tack it if you want to go that route. Iv got a welder and its portable if you need it to be, or come to my shop and ill weld it on for you
 
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