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Yz125 Gearbox strength/longevity?

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Hi,

Currently I have a 2016 yz125 which has 280 hours since new. It was ridden and raced in state level enduro for the first 250 hours of its life. Now it's also racing national enduro and state motocross (In Australia).

 

The bike has had one bottom end at 180 hours, and soon to be another one. It's port and polished for top end power and is ridden that way - but always using the clutch to change gears.

 

The gearbox has never been touched, and my question is how long will it last without replacing internals? Are they fairly strong? Or will they need some work? Thanks 20190920_162603.thumb.jpeg.bb2ec47ba405f9581070fd2bcb85fc50.jpeg

 

 

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Yes they are but inspect the gear coggs when have apart again.  Once they get rounded will start slipping.  Pretty rare with these trannys tho . Obviously you keep up on oil changes

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1 hour ago, john stu said:

Usually 281 hours is where the gearbox lets go....

Ha! Mr funny man the newer 125 transmission is a better design than the yz250's. 

I'm sure i got you beat on number of running hours on my 06. Have owned it since brand new. Unless things like oil changes where not done etc. 

I'm sure it's all good have never had a problem with mine. Since your going to rebuild the engine just check it for wear. Maybe replace the spacer washers if they are worn they are cheap and it will help tighten things up.

 

 

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My 2010 YZ125 (purchased as a new leftover in 2012) was a notchy shifter pretty much from the second season on (@20 hours)

Missed shifts, false neutrals etc. always during the 4th gear upshift.

 

For some reason it 'fixed itself' with only occasional missed shifts during the following seasons but by the 120 hours mark it progressively got worse,

popping out of gear on a jump face during the last track day of the season was a wake up call to look into it.

 

Last winter I split the cases (did the crank/rod as well) and the gear engagement dogs and windows did show some wear

but nothing major, a shift fork also showed signs of being bent a little (likely from forcing it into gear during the missed shifts)

so three new gears and a new shift fork later it now shifts perfectly.

 

Edited by mlatour

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My YZ125 was somewhere around 400 hours (not sure exactly because I was on the 2nd or 3rd hour meter) and apart for a new crank when I noticed the transmission bearings needed replacement (not smooth).  The gears themselves and the shift forks looked fine, so I just replaced all the transmission bearings.  Be forewarned--that tiny little seal for the clutch actuating arm inside the flywheel cover is a PITA!

BTW, my maintenance schedule is gear oil change every 10-12 hours, and I just use whatever motor oil is on sale.

Edited by rpt50
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