Front Sprocket Welded on

[StumpyFingers]

That looks like a moron was let loose on it.
It may require a new driveshaft as well if too bad.

[piguglyshandydrinker]

Looks like I'm, the only one that thinks the sprocket looks in reasonable nick - all things considered.

Slap another chain on it & worry about it in 10 - 20,000 miles time!

Phil

[whynot]

Slap another chain on it & worry about it in 10 - 20,000 miles time!

I'm starting to think that's not a bad idea ....
I'm just a little worried about the sideways movement in the sprocket.

[btbloke]

look at the difference in height of the teeth phil, the pic below is one from another thread, well worn and bent over but the teeth are longer and the shamferred tips of the teeth are quite clearly shorter and more worn down than the ones bent over below. You should at least be able to see the top of the tooth between the chain links in the bottom pic above shouldn't you,checked my chain etc and the tooth is definitely further though the chain link than this one.And look how far in it is away from the retaining plate groove,it's way out of line with the rear sprocket.I'm surprised the chain lasted as long as it did and if it snapped it might miss the case saver bar in the cover completely and damage the crankcase if it went.


I would get that weld off at least just to check out the splines behind it,at least you would know why it was done. You never know it might have just been a cowboy mechanic who didn't know a new retaining plate was only a couple of quid or he just couldn't be bothered to order one and took the muppet option with an arc welder. At least a new sprocket will see you and the new chain round europe with no worries because if it was me I would have this on my mind all the time I was riding and it might spoil your enjoyment of the trip if you are anything similar. I'd say worth a go just for the peace of mind.
Just my opinion of course we're a varied lot on here so at least you get diversity.

[whynot]

I would get that weld off at least just to check out the splines behind it,at least you would know why it was done. You never know it might have just been a cowboy mechanic who didn't know a new retaining plate was only a couple of quid or he just couldn't be bothered to order one and took the muppet option with an arc welder. At least a new sprocket will see you and the new chain round europe with no worries because if it was me I would have this on my mind all the time I was riding and it might spoil your enjoyment of the trip if you are anything similar. I'd say worth a go just for the peace of mind.
Just my opinion of course we're a varied lot on here so at least you get diversity.

Yep good point.

I took it down the road to the local workshop and the guy there basically said it was a no-go on welding it again, as the heat would damage the shaft and then it would come apart eventually.

He also said that a rebuild and new shaft would cost a fair bit, so just to look for a new engine ...

Will have a think over the weekend, but it looks like a good £800-1000 for an engine change.

[Plasnart]

I don't think the movement of the sprocket is a problem, I think it's designed to be like that, my 8000 mile bike is the same. The clamp plate stops the sprocket coming off but it doesn't hold it tightly, you can move it sideways a little and it can waggle (dampened by its rubber side plates. This must be to allow the chain/sprocket to move and stay aligned.

This is probably what causes the wear to the shaft, mine was bone dry so I greased it up recently. If it were fixed the splines wouldn't get worn down.

[Cabby]

You don't think that the weld is just there to hold the sprocket in place 'cos someone misplaced the retaining plate and had a welder handy but not the part do you?
If you can remove the weld well enough to get the sprocket off it may be that you can replace it with the retaining plate (OR 2 retaining plates as Grendel of this manor did)

These sprockets are supposed to have a little movement on them

I think you'll manage to work round it......

Failing that......I got a replacement engine off ebay for £200 and it's in the bike running now....I'd never done tha job before but it wasn't so hard or complicated...took me a while but I'm a messer...

A 650 will cost more but it'll be worth it.

You need a manual....I used haynes.

[btbloke]

Your welcome to bring it up here and I'll give it a once over,I've got an angle grinder to take off the worst of the welds and a Mig to tack it back on but you'd need to buy/borrow/beg a dremel from somewhere to do the inside of the splines.And worth ordering a new retaining plate and some bolts,if you don't get to use them on this bike they can be spares for the other bike for the trip.
As for the welding,I would disagree with the guy,as long as you cooled the shaft correctly it should do no furhter damage if it did have to be re-welded,If there were any damage it would have already been done with the amount of weld on it already,at least if it was re welded in the correct position it would be on for another 20k and not a worry.Especially if was welded properly.Some guys on here have ground off and rewelded several times with no ill effects.

[whynot]

Your welcome to bring it up here and I'll give it a once over,I've got an angle grinder to take off the worst of the welds and a Mig to tack it back on but you'd need to buy/borrow/beg a dremel from somewhere to do the inside of the splines.And worth ordering a new retaining plate and some bolts,if you don't get to use them on this bike they can be spares for the other bike for the trip.
As for the welding,I would disagree with the guy,as long as you cooled the shaft correctly it should do no furhter damage if it did have to be re-welded,If there were any damage it would have already been done with the amount of weld on it already,at least if it was re welded in the correct position it would be on for another 20k and not a worry.Especially if was welded properly.Some guys on here have ground off and rewelded several times with no ill effects.

Thanks for the offer, i'll have a think about it over the weekend and let you know. Where can i get the retaining plate and bolts from?

[BobA]

I'm sort of with the others here. It's been bodged, but actually not the worse bodge.

Usually, once you go down the route of welding the sprocket, you're committed to welding the next sprocket once it's worn out.

In your case, it would seem the band of weld has just been used to retain the sprocket on the shaft, so it's not actually bonded to the shaft.

If you can get a grinder and carefully remove the weld, you could then use the grinder with a thin disk, or a dremel, to try and reform the splines out of the excess weld. To be honest this would be easier if the sprocket wasn't in the way, but cutting it off will be even more difficult. Once you've spent some time grinding the welds so the old sprocket slides off, or a new one slides on, you could even reform the valley that the retaining plate sits in by carefully holding the grinder, putting the bike in gear, and slowly forming a slot on the spinning shaft.

Welding a sprocket on isn't the end of the world, as long as you weld a new one on, it is in the right place on the shaft and aligned with the rear sprocket, and you keep a hose running ready to cool the shaft so the oil seal doesn't get damaged.

Failing that, a secondhand engine would do the trick I reckon.


Good Luck



Bob