Yamaha TRX850 Enthusiasts Forum

Hi,

I replaced the chain and rear sprocket, the front one looked good and didn't respond to trying to get it off anyway. Now I can't adjust the chain consistently, it goes from very tight in places to slack - does it appear I have a bike with a bent output shaft, and if so am I looking at a big repair bill?

Highly unlikely, borderline unheard of. Are you sure the front sprocket hasn't been welded on not quite centrally or something else as stupid? And play in the rear sprocket?

True to it being highly unlikely , in any case if you do have a bent output shaft, the tight/ loose feel would come about at every 360 of the front sprocket.
Feel for that....maybe take the chain off again and start the motor with a middle gear running and watch the sprocket.

The rear is sound, no play anywhere. I'm trying to get the front sprocket off, but even with the back end on the ground and the wife holding the front and rear brake on the sprocket still turns?

wrap a towel around a stout piece of wood and put it through the rear wheel against the swinger, use it to lock the rear end up. Use a T bar on the socket with a long piece of pipe and undo with that.

I would expect it's the chain and not a bent output shaft causing the slack/tight.

Rich wrote:wrap a towel around a stout piece of wood and put it through the rear wheel against the swinger, use it to lock the rear end up. Use a T bar on the socket with a long piece of pipe and undo with that.

I would expect it's the chain and not a bent output shaft causing the slack/tight.

Thanks Rich, this is the second new chain so suspect the front sprocket, will try the bar/pole trick tomorrow. Thanks for all your replies guys

use a 1/2" drive electric impact wrench if you can afford one, about £50 from machine mart and one of my better buys. I bought a mains pwered one so I wouldn't have to worry about batteries - but you can also get a cordless version

I'll have to take it in. Even locking the rear wheel with a bar doesn't lock the transmission, the socket just rotates when I turn the socket on the nut (lefty loosey).

???? do you mean the nut has rounded off or the threads have gone on the output shaft? It should lock the drive sprocket unless there are no splines on the output shaft If you need another shaft let me know I probably have one here.

Mav617 wrote:I'll have to take it in. Even locking the rear wheel with a bar doesn't lock the transmission, the socket just rotates when I turn the socket on the nut (lefty loosey).

Strange ... may be a bit of a silly question, but the chain is connecting the (front) sprocket with the (rear) gear wheel while trying to loosen the nut?

If so, I would very much like to see that in the flesh

Curious greetings from Munich!

There is a tab washer under the nut which is bent up against 1 or 2 of the nut edges.
Have you put a screwdriver in between these and flattened them to rest back down against the sprocket???
The thread is a normal everyday right hand thread so anti-clockwise will undo the nut.

Hi,

Yes, the chain is on between front and rear sprockets, and I've flattened off the tab washer. The output shaft still turns when pressure applied on the sprocket nut, with the bike in gear and a breaker bar between the spoke and the swing-arm to stop the wheel turning. The chain doesn't seem to fit the sprocket tightly enough, I wonder if the previous owner used a different sized (520/530) sprocket for some reason, either way I can't seem to get the bugger off!

HolerTogni wrote:

Mav617 wrote:I'll have to take it in. Even locking the rear wheel with a bar doesn't lock the transmission, the socket just rotates when I turn the socket on the nut (lefty loosey).

Strange ... may be a bit of a silly question, but the chain is connecting the (front) sprocket with the (rear) gear wheel while trying to loosen the nut?

If so, I would very much like to see that in the flesh

Curious greetings from Munich!

Aaah, I misread "socket" for "sprocket"

But if it is the socket, which turns on the nut without loosen the nut, then I can only think of two reasons:
Either the socket is way too big , or the thread of the nut and/or on the output shaft is ruined.

... a third reason would be that the drive shaft could be broken, but I think you can still drive the rear wheel with engine power via the gearbox?!?

Thinking greetings from Munich !

Hi Mav617!

Mav617 wrote: ... The chain doesn't seem to fit the sprocket tightly enough, I wonder if the previous owner used a different sized (520/530) sprocket for some reason, either way I can't seem to get the bugger off!

So, on the big screen now (not on my mobile).
When submitting my last post, I didn't see yours before, for whatever reason ...

If the sprocket turns despite (!) the chain should prevent it from doing so, the sprocket and the chain certainly don't match like they should

Either you mount the old chain and gear wheel again to be able to remove the old sprocket or you use an air-hydraulic or electric impact wrench as suggested earlier in this thread.

Proposed greetings from Munich!

I saw a mains powered electric impact wrench on Amazon for about £60, puts out a claimed 460Nm which should undo just about anything, provided your sockets can take the impact. Cordless wrenches tend to put out much less (unless they are REALLY expensive) and the windy guns are generally only as good as your compressor. I nearly bought one but really can't justify it at the moment, first tough nut I'll be placing an order though.

A good impact wrench and you shouldn't need to involve the wife on brakes, jamming wheels etc (all good ideas, though) as it will just frighten the nut off.