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Yz 125 primary drive gear problem

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When I ride my Yz the primary drive gear bolt unscrews itself. I did put a medium strenght thread locker on it but it does not help. Anyone has an idea how can I sort out this problem because I don't want to mess up the threads on crank or broke the bolt head?

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Well one of you guys must be wrong there either is or isn't a lock washer. I don't know how the guy that owns it would would say there isn't one if there is it's very easy to check

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If you are talking primary drive gear on end of crank in the case that drives the clutch then yes NO washer.

 

If you are talking primary drive sproket then YES it does have a lock washer.

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I was thinking about primary drive gear that turns the clucth not primary drive sprocket :) Anyone has any ideahow to fix this? :(

My mistake too. I thought you meant the primary drive sprocket. Anyhow, locktite will keep that nut from loosening, but it has to be applied to clean threads first. Spray the threads on the end of the crank and the threads on the nut itself with some brake cleaner/etc, and then reapply the locktite, torque to spec, and you will be good to go.

Edited by MANIAC998

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Yeah,I will do that for the 4th time and I hope it will work this time because I don't have any other idea what to do besides weld a nut to a gear

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I had the same thing happen to my 2003 yz125 (primary drive bolt backing off), haven't tried replacing yet because I also noticed more play that I though would be normal between the gear spline and the crank spline.  Does anyone know how much play there should be between the gear and crank? 

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