General guide...

If your putting on a new chain .. a new front sprocket will ensure you get your moneys worth from the chain.

On the rear sprocket .. new one every 2 front sprockets.

Thanks so much for the detailed and very informative reply mollydog and you too Warin. I had been told a few times that when you replace a sprocket you need to replace both sprockets and the chain as a set. Guess that's how mechanics make their money..

So as I'm halfway through a 4000 mile trip I'm wondering how urgently I should replace my sprockets as it will be much less of a headache/cheaper to do it when I get back to London. Weirdly it seems that my front is much less worn than my rear although I only have these terrible photos:




thanks!

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http://www.guyfixsen.com
http://wanderinggoo.blogspot.com
F650GS twin - Enfield Bullet 350 - Honda XL250 Degree

oh and incidentally I'm on an F650GS twin and the sprockets/chain are good "heavy duty" items I fitted myself in the UK.

__________________
http://www.guyfixsen.com
http://wanderinggoo.blogspot.com
F650GS twin - Enfield Bullet 350 - Honda XL250 Degree

Sprocket discussion also at http://www.horizonsunlimited.com/hub...er-8500k-80861 including some of the same pictures

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TBS.com

Front sprockets are much cheaper than rears.. thus someone has not replaced the rear when they should.

That rear needs replacement AND you should replace the chain at the same time. If you are counting on the reliability of the bike then replace now. If you can deal with a breakdown (accommodation, any transport, food) and replacement more cheaply than the replacement now ... ok.

Goo,
Your rear sprocket looks pretty bad! If you're re-newing the rear, then for sure do the front as well. If the front really looks OK when you've got in your hand, keep it for a spare. But I'd sooner carry a NEW spare front.

This is ALL easy maintenance, not a big deal ... so if you can lay hands on the parts ... do it!

UNUSUAL in my experience that the rear has worn before the front. Perhaps the rear is Aluminum or of lesser quality?

In any case, I just hope your chain still has some life left in it ... and I hope you can determine where your chain is in terms of it's remaining useful life.

A bit hard to explain. You just have TO KNOW. BUT ... if no kinks, if not pulling away too much at 3'Oclock position off rear sprocket (no more than 1/2") and not needing adjustment ... then maybe it's OK ?

If any question about it, replace it. Not worth the heartache and hassle of failure in Bumfucistan.

Normally ... when at or near home with parts sources at hand, one would replace the lot. But on the road you have to improvise and learn ways to extend chain life ... especially true if no spares at hand. So that's why I change front sprockets about 3 to 1 to a rear sprocket or chain. Everything lasts longer and it's a cheap fix.

Hopefully you can just swap in a NEW rear sprocket and make the 2000 miles back to London. Let us know how it goes and where you've found parts!

Hey mollydog -

thanks again for the great info! Will definitely replace sprockets. Would be great to hear a bit more detail on how to verify the chain condition:

What exactly constitutes a kink? I noticed one link was not in line with the rest of the chain in the 'looser' lower part between the sprockets but it moved easily back into line with fingers.

And what do you mean by 'pulling away'? and do you mean 6'o'clock i.e. bottom of rear sprocket?

The chain doesn't seem to need adjustment although I'll properly check that when I get back to where the bike is on Tuesday.

*thanks*

Guy

__________________
http://www.guyfixsen.com
http://wanderinggoo.blogspot.com
F650GS twin - Enfield Bullet 350 - Honda XL250 Degree

Check several points on the chain- some places will be worse than others.
Check the chain daily before you ride, and start making backup plans for getting it serviced before it's totally gone. Email or call some shops ahead on your route to see who has got what you might need.

...............shu