Front sprocket tab washer - what's the secret for removal?

[paturoa]

If it is a bent up washer then a hammer and a big screw driver. Do NOT hit it hard as the output shaft normally has ball bearings and they don't like sideways wacks with hammers!

Gently tap it till it is flat. Then the next problem is getting the nut off.

A big arsed piece of wood through the spokes across the swing arm, foot hard on the foot brake and get another person to take the nut off. Do nt munt your spokes!

[dmoo1790]

Mate take it into a shop & get them to do it..
If yer can't figger out how to get a tab washer undone
you shouldn't be anywhere near a motor bike with a
spanner unsupervised..

Tongue in cheek maybe? I usually figure things out for myself eventually. Been spannering on my own bikes for decades and lived to tell the tale. And anyway I want to work out a good way to change the sprocket on a trip away. Gear down for the gnarly stuff and gear up again for the long haul. So the shop's not really an option.

[dmoo1790]

Two secrets. First, use the old man's wood chisel. When you're arse recovers re-grind your own cold chisel the same shape and keep it forever.

Second, don't smack the shit out of the bloody thing when you're re-fitting it, not only are you making it difficult to remove but you're likely to fuck the bearing right behind the sprocket.

No worries. I'm not the type to smash stuff. If anything I'm too careful. You're dead right about re-fitting it. I want to make it easier to get off next time so I'll try to bend it in such a way that I leave a gap at one corner of the bent bit to get a lever under next time.

[dmoo1790]

If it is a bent up washer then a hammer and a big screw driver. Do NOT hit it hard as the output shaft normally has ball bearings and they don't like sideways wacks with hammers!

Gently tap it till it is flat. Then the next problem is getting the nut off.

A big arsed piece of wood through the spokes across the swing arm, foot hard on the foot brake and get another person to take the nut off. Do nt munt your spokes!

Yeah, I'm hoping the nut will not be too bad. I plan to lock the rear brake. I can do this with a spacer in just the right spot between the brake lever and frame. I'm not a fan of putting anything through the spokes even on a bike with cast spokes. Be interesting to see how well the brake holds and if the cush drive absorbs much torque.

[AllanB]

A big arse breaker bar or slipping a length of galv plumbing pipe over the end of the rachet is the best way to crack the sprocket nut ie heaps of leverage.

[pete376403]

Yeah I meant a cold chisel (not a wood chisel).

Another useful tool is a piece of pipe or bar witha length of chain welded to one end. Wrap the chain around the front sprocket to hold it while loosening or tightening the nut. Better than stressing the spokes sideways - they're only really intended to be tensioned lengthwise.

If you had a KLR you could get a "prevailing torque" nut (self locking) from EagleMike
http://eaglemike.com/Prevailing-torque-nut-PTN.htm and forget about the tab washer.

[Subike]

Yeah I meant a cold chisel (not a wood chisel).

Another useful tool is a piece of pipe or bar witha length of chain welded to one end. Wrap the chain around the front sprocket to hold it while loosening or tightening the nut. Better than stressing the spokes sideways - they're only really intended to be tensioned lengthwise.
:

now that sounds like one of them tools every sensible man should have, I think I will have to make one of them.

[Crisis management]

I want to make it easier to get off next time so I'll try to bend it in such a way that I leave a gap at one corner of the bent bit to get a lever under next time.

Couple of things, The KTM sprocket relies on being correctly torqued down to ensure the two oil seals (wiper seal and O-ring behind the wiper seal wear bush) behind it are compressed correctly to keep the oil in the gearbox, on my 640 that has been an issue as it vibrates everything loose. So, make sure you have got it tight enough and the tab washer is correctly folded back on the nut when you are finished.
Undoing that nut in the field is usually problematic if you want to do a gearing change as it takes a big bar and lots of grunting, simply carrying a suitable socket and bar around is problematic, look at how you will store it.

You may be better to look at a complete gearing change (front & rear sprockets) and live with the compromise for the DB rather than trying to change sprockets on the go.

Edit: one last thing, the weakest point is not the tab washer in this assembly (assuming the 690 is like other KTMs). The nut is aluminium and is intended to be a one use item, so carry a spare.

[unstuck]

A big arse breaker bar or slipping a length of galv plumbing pipe over the end of the rachet is the best way to crack the sprocket nut ie heaps of leverage.

Not so good for the rachet though, Better of with a power bar. I keep an old wood chisel for those tabs.

[dmoo1790]

Couple of things, The KTM sprocket relies on being correctly torqued down to ensure the two oil seals (wiper seal and O-ring behind the wiper seal wear bush) behind it are compressed correctly to keep the oil in the gearbox, on my 640 that has been an issue as it vibrates everything loose. So, make sure you have got it tight enough and the tab washer is correctly folded back on the nut when you are finished.
Undoing that nut in the field is usually problematic if you want to do a gearing change as it takes a big bar and lots of grunting, simply carrying a suitable socket and bar around is problematic, look at how you will store it.

You may be better to look at a complete gearing change (front & rear sprockets) and live with the compromise for the DB rather than trying to change sprockets on the go.

Edit: one last thing, the weakest point is not the tab washer in this assembly (assuming the 690 is like other KTMs). The nut is aluminium and is intended to be a one use item, so carry a spare.

Thank you. The last point about the alloy nut was not something I had spotted. The nut is indeed made of cheese. I've pretty much given up on the idea of road side gearing changes. For the DB and other trips I think I'll be stuck with standard gearing. Why did KTM not fit a wide ratio gearbox on the 690? Or at least a lower first gear or overdrive sixth? Such a brilliant bike with a stupid design flaw in the gearing.

[tri boy]

XRL front sprkt held in place by two 6mm bolts. Easy peasey in the field.
Fatty the scrambler, big arse nut toruqed to about 95ft/lb. Not so easy

[Woodman]

Thank you. The last point about the alloy nut was not something I had spotted. The nut is indeed made of cheese. I've pretty much given up on the idea of road side gearing changes. For the DB and other trips I think I'll be stuck with standard gearing. Why did KTM not fit a wide ratio gearbox on the 690? Or at least a lower first gear or overdrive sixth? Such a brilliant bike with a stupid design flaw in the gearing.

My KLR hs the same sprocket nut set up which is a pan in the butt, but only at chain and sprocket changing time. Surely the 690's gear ratio can't be that bad with all that HP and lightness? Done 3 dbs on the klr with standard gearing with its horrible gap between 1st and second and never wanted for a lower gear. Thats what the clutch is for.

[dmoo1790]

My KLR hs the same sprocket nut set up which is a pan in the butt, but only at chain and sprocket changing time. Surely the 690's gear ratio can't be that bad with all that HP and lightness? Done 3 dbs on the klr with standard gearing with its horrible gap between 1st and second and never wanted for a lower gear. Thats what the clutch is for.

And last DB I was fanning the clutch so much over the Awakino I could hardly grip the next day. Sure, I'm not that strong and I'm a crap rider but maybe 10% lower first gear would have been a lot easier. I have read about many other 690 owners gearing down for tough, slow stuff so I'm not totally alone in my opinion. Also the 690 has little flywheel and stalls easily at low revs. It's tallish as well. And lighter than a KLR but still a heavy dirt bike. All adds up to more grief than necessary when a better gearing design could have made it damn near perfect. Particularly galling when the 530EXC apparently has an ideal wide ratio box so KTM know how to do it but they cut corners on the 690 design.

[Transalper]

.... I've pretty much given up on the idea of road side gearing changes. For the DB and other trips I think I'll be stuck with standard gearing. ....

I did a few mid trip gear changes on the DR650 when using it as it was the easy 3 screws in a plate and it all falls off job, but seeing the big single nut and penned washer arrangement and already doing a couple of experimental changes at home there's no way I'd be doing that on the road, especially not with what's in my on bike tool kit.
Rather than using the stock gearing or my trail gearing I chose a compromise gearing, lower than stock to help but not so low it stuffs the highway as my trail gearing did.
I've actually found the ratio to still be not too bad on our Waimak singletrack so maybe my 'trail' gearing was lower than needed.
So if you don't like the stock gearing so much and your trail gearing is too low for the long distance and highway sections then why not just lower it a bit, not the whole way.

[dmoo1790]

I found an idea in a thread on advrider about removing the front sprocket on a 990: http://www.advrider.com/forums/showthread.php?t=344625

So after finding the spanner (which I thought was totally useless) from my tool kit I tried fitting it in a position which would work for undoing the nut. Like this:



It looks like the spanner bend is designed to fit over the swingarm. So carefully rocking the bike backwards should break the nut loose. It will be cool if it works but I'm not going to try until I can get a spare nut or two. Also not sure if the same idea would work for tightening the nut.

The other end of the spanner fits the rear axle nut but I'm wondering what the notch is for. Anybody know?