DR350 Primary drive nut stripped

Yeah, I stripped it with an impact.  

I didn't know that it was a left handed thread.  Most of the damage is done to the nut, and my ego.

Surely I'm not the first person to do this, so what is the fix? 

I can buy a replacement nut, and it looks like I could re-thread the crank if I knew what metric thread it was.

Does anyone know what thread it is?

Any other help would be greatly appreciated.

Thanks,

Jeff 

 

1993 DR350 (dirt)

Take it to a machine shop that has metric dies if you can find one. They can quickly guage the threads. Don't know where you are but in the US it probably won't be easy to find one that has a left hand metric die that large so you might have to buy one yourself. Have them "chase" the threads with the correct die. Buy a new nut. Observe proper torque when you reassemble. Use some oil-resistant removable thread locker (NOT red loctite!) and keep your fingers crossed.

Revising....

So I've been thinking about this a bit more. Here are some other things you might want to try before taking it to a machine shop.

The crankshaft is a hardened piece and should be much harder than the nut so it may be that what you think are damaged treads on the crankshaft are actually just fragments of the damaged nut. I would suggest that you examine the threads on the crankshaft closely with magnification as it is entirely possible that you could use a thread cleaning file to remove fragments of the nut and get by without chasing the threads. That is still preferable but I think it will be hard to find a shop with the correct left hand thread die. Obviously you still need a new nut and be very careful to observe proper torque when tightening.

Oh, and you NEED a workshop manual to work on this bike. Check thisoldtractor.com for a free downloadable manual.

Thanks for the thoughts.  I'm gonna buy a die for it and chase the threads just to be sure.  I'm gonna measure the major diameter of the threads but I'm just not sure about the pitch.

 

I was downloading the free manual as I was stripping the nut...IRONY!!!

 

Anyone else have any idea what thread the primary drive nut is?

 

Thanks for you help.

Mystery solved!  Hope this helps others.

 

I ordered the nut ($5) from my local Suzuki shop.  Once it arrived I measured the thread per my machinist handbook using thread gauges and calipers from work. 

 

The nut has a Left Handed 18mm x 1.5mm thread.

I found a die online with this thread for $30.  I ordered it.  It should be here next week.  I plan to chase the threads with the die then install the nut with thread locker and hope for the best.

 

Has anyone tried to install a locking washer with a bent tab on this nut, similar to the one on the clutch nut?  Seems like that would fix the loose nut issue.  Of course we would have to locate the correct washer for the task that fits the keyway.  probably too much to ask.

 

Oh, during my research I learned from Babbits that the nut that I stripped is used on a lot of vehicles.  
See below.

Assemblies where 09140-18012 is used

Interesting thought but don't the locking washers on dr clutch shaft as well as the one found on the drz drive sprocket nut fit on a splined shaft? I would think that such a thin washer fitting in just a key way might not be as effective. It would be nice to not have to tear into a brand new motorcycle and lock tight the primary nut though, case in point drz400.

Yeah I know...

I was just thinking that it would be an extra layer of protection along with the thread locker.

I'm gonna check into it.

Update:

I finally got around to fixing my DR.  The die worked great and I was able to torque the nut after adding loctitie.  The threads cleaned up and looked great.

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