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Discussion Starter · #1 ·
I have an 85 TRX125 that I picked up for my girlfriend to ride. It runs great but the problem is it wont move. I had to replace the chain and sprockets because the PO somehow wedged the chain behind the subtransmission and broke about 3 teeth off the front sprocket.

So I got that all swapped out, but now if you shift it into gear the rear wheels lock and it does not move if you give it gas. Anyone have any inisght into this?

Thank you in advance and I apologize if I posted this in the wrong section, feel free to move
 

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Tough call on this - not enough info and confusing description.

When you say the wheels lock, does this mean it will not move forward or backward? And is the problem the same if the motor is running or not?
 

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Discussion Starter · #3 ·
Ok I figured I would get a general description of the issue out there and provide more details as needed. So when you shift into any gear once in gear the rear wheels lock and the quad will not roll forward or backward motor running or not. With the engine running while in gear not matter how much throttle is applied it will not move.

I have had the subtransmission apart a couple times to make sure everything is lined up and installed correctly.

Not sure what else it could be.
 

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Does the motor sound like it's straining to move when you give it throttle or does it just rev freely? If it is straining, then it's probably the tranny. If it revs freely, then it's probably the clutch. If it's the tranny, then it might be in 2 gears at the same time. This can be caused by a broken shift fork. I hate to ask you to do this, but take the sub-transmission off, leave all the parts out, put the cover back on. Put it in gear and see if the if the rear end still locks. If the rear end moves and the motor sounded as if it were straining when you gave it throttle, then start the motor, put it in gear and see if it acts the same. If the rear end still locks, then it's my guess that you either installed the engine sprocket wrong, or got the wrong sprocket.
 

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Discussion Starter · #5 ·
Here 2 help, it does strain while giving it gas, and that was actually my next though to attempt. I was going to rip everything out of the subtransmission and see what happens.

The sprocket being installed wrong had crossed my mind but wasnt sure if that was even possible.

I will check out both of those scenarios this weekend and report back.

Thanks again. I appreciate the help.
 

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When I mentioned the engine sprocket being installed wrong, I should have also mentioned that there was 2 different sprockets depending on the year of manufacturer. Some parts list will show one sprocket to engine #???? and a different engine sprocket from engine #???? The difference is in the depth of the sprocket and it is only a mm or 2, but it will prevent proper operation. Since the engine strains as accelerated, I think you can discount a clutch problem.
 

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Discussion Starter · #7 ·
Ok, I ripped all the guts out of the subtransmission this weekend, and now shifting into gear does not cause wheel lock up, but it still wont move. And it still seems to be struggling when in gear while on the throttle.

Any other ideas? I really dont want to have to split the cases on this thing.
 

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on 85 model you have to have high speed gear, bush and snap ring, then super low drive gear on the counter shaft for power to transfer to front sprocket. This will require at least (1) shift fork. This will allow you to have (4) forward gears, no super low and no reverse. Idid this to TRX 125 engine I got for bike project- didn't need reverse, super low was chewed up and caused lock up like what you described earlier. Hope that helps.
 
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