New sprockets on a half worn chain?

[Jug]

I suspect most of you will greet this proposal as if it were heresy but a half worn chain is still within spec.

Background.. my 990 is about finished with its front & rear sprockets so I thought I'd measure the chain. The manual quotes the length for 18 links but my digital calipers don't open that far so I recalculated it for 10 links and then measured the chain (under tension) at the pin centres.

10 pins length --- New 142.875 mm --- Limit is 144.304 (which is 1.429 mm or 1% stretch)
Mine is at approx 143.5 mm which is 0.625 mm stretch or 0.44%.

So my quandary is do I spend £41 on just new sprockets to finish off that chain (and maybe expect shorter sprocket life) or £97 for chain & sprockets?
BTW I have no idea how old that current chain is, it could be the original so has about 21,000 miles on it but it is in great condition and has no tight spots (DID chain).

Let the roast begin..

Edit: just checked the worn rear with a magnet and it's an alloy sprocket, so maybe that explains why it seems to have worn out prematurely.

[jer r1]

That's one way to get more posts on the forum. I think the amount of droop on the chain when held out on it's side is also to be taken into account. Probably wrong on that fact but hey-ho

[Jug]

I do already have a full set that came with the bike (AFAM brand) which are pretty expensive, problem is the rear sprocket in that set is also alloy.

So I could..
A) Just use the sprockets from that set now and in the future use the AFAM chain with new steel sprockets.
B) I could use the AFAM chain and front sprocket now but buy a new steel rear instead of using the new alloy one, but then have that alloy rear left on the shelf doing nothing.

I would prefer option A as that at least uses up that alloy rear sprocket, and also finishes off the chain.

[Robbo87]

My opinion, and it is only my opinion (and possibly Roy's ), and what I would do to get the most possible mileage, is put on a couple of cheap and cheerful sprockets to see your old chain out and only then replace the whole shebang with a quality set.

[bkingalan]

Just a pitty Roy doesn't ride KTM put the full set on and sell Roy the old ones then you know they won't go to waste simple

[Jug]

I'd imagine once Roy had finished haggling I'd just as well give them to him.

[ptolemyx]

You ought to end up with steel sprockets and a new quality chain (could go to the expense of a "Supersprox" rear which has a ring of steel teeth on an alloy centre). Even anodised alloy sprockets don't last long. In the meantime I'd do option A hoping the replacement alloy sprocket will last the remaining chain life.


....BTW what lubrication system do you use on the chain and sprockets? I clean mine regularly and give the chain a coat of chainsaw oil.

[julesh]

Change the lot it's £97 not £970

[Jug]

....BTW what lubrication system do you use on the chain and sprockets? I clean mine regularly and give the chain a coat of chainsaw oil.

I clean it regularly as I hate to see my chain looking dirty. To clean it I mainly use old engine oil though I occasionally use WD40 if it's really dirty, like after a trip. I generally don't like using solvents as I think it strips the roller inners of oil.

I tend to lubricate with gear oil when in the garage or via a chain oiler on the bike. I'm also currently messing around with grease and might switch to using a concoction of grease and oil for lubing when in the garage.

My chain and sprockets are well taken care of.

[Jug]

Change the lot it's £97 not £970

It's not the point though.. do you change your brake pads at 50% or when they are approaching the wear marker?
They're only £40 a set.. cheap insurance..

Edit: Ah.. but you would if you were fitting new discs... scrap that analogy then.

[billinom8s]

how well do the new sprockets fit with the old chain? If it's propper baggy in there, your questions have been answered, if it was me, i'd do the full swap and then stick the chain in a tub of oil for a 'break in case of emergency' kind of situation. The only time i put alternative sprockets into opertion with an ol chain is on the trackbike when i change the rear one out depending on circuit or tyre wear.

[Jug]

how well do the new sprockets fit with the old chain? If it's propper baggy in there, your questions have been answered,

That is a test I did plan on doing, stick the new rear in the chain while it's still on the bike and see how tight it sits, then do the pull test to see how far it can be pulled off it. I'll then decided whether the chain can stay on, if it gets removed then it will be binned as I don't have more master links for it.

[Tvrv37]

I had a chain snap on me once pulling out of a junction 2 up. the chain cut through the guard and embedded in the swing arm. Cost a lot more than £97 to sort out.

[Jug]

I had a chain snap on me once pulling out of a junction 2 up. the chain cut through the guard and embedded in the swing arm. Cost a lot more than £97 to sort out.

What's the background story - was it an old chain or just a faulty link?

[Tvrv37]

It was a few years ago before modern heavy duty affairs you get now. It was within its serviceable life though, not rusty. It was a failed link. After that I just replace chain & sprockets together.