Just for infor the machine is an Aprilia RS 250 with no pervcievable wear on the sprockets but the chain has staretched to the extent that it's shitting me up.

Thanks for all the good advice - I have to agree with Baboon though; chains are easy to repair on the fly.

Erm........arriving fashionably late. If I may throw in my 2 cents worth:

From an 'engineering' perspective (I'm not a engineer), just had a few bikes in my time. I used to change out chain and sprockets as a set, something to do with a worn sprocket is not nearly as well defined as a worn chain. Do not run new chain on worn out sprockets because it can cause the chain to wear rapidly. The pitch of the new chain is much shorter than the effective pitch of the worn sprocket, so the total chain load is concentrated on the final sprocket tooth before disengagement - understand that my fine feathered friends?

Then, when the chain disengages from the sprocket the roller is jerked out of the hooked portion of the sprocket tooth and the results in a shock load on the chain as the load is transferred from one tooth to the next...........breath out.

Fuck, listen to me sound like I know what I'm talking about.

To add to the argument, it is well known that softer materials eat away at harder ones?? Phosphour bronze wheels would remain intact and the harder mild steel covers would be eaten away at the anchor points.

From my windsurfing days, people got all uppity at putting taught nylon straps on a board, a few hundred miles on the road and the board would go airbourne, the soft board had chewed through the strap, not vice versa.

BC, you may be right but I couldnt quite tell what you were trying to describe as relates tothe question at hand!

BB, you sound like you know what you are talking about because, apparently, you do!

Baboon, is, of course, correct that it does depend what you are doing with your bike which final drive system suits best. Chains, though requiring the most maintenance are the easiest to work on. They are also technically simpler than a shaft drive and, as stated, easier to "bodge fix" if you are in that situation. I am not certain but I would also imagine that on average a chain drive would be lighter than a shaft drive although, with clever design, maybe not by much (the shaft drive unit can be incorporated as a structural element of the swing arm, clearly a chain cannot!).

A modern belt drive is lighter than a chain, lasts longer in normal road use, doesnt stretch and needs no servicing. Belt drive is also quieter and smoother than chain. They can be expensive to replace but they will work out cheaper due to long replacement intervals. The weakness of belt drive is that it is unsuitable for off-road use as the belt can be easily damaged by grit etc lodging between the belt and pulley. If a belt does go, it is likely to be sudden and total failure due to damage not wear!

But the simple answer is still - "Best practice" is to replace chain and sprockets as a set

Originally Posted by mush_dad

Check the feel of the new chain in the sprocket teeth, if it's a bit slack or the teeth are starting to become hooked, then it's new sprockets I'm afraid. If the links of the chain are snug in the teeth, then leave it until next time.

Unless of course you're thinking of 120mph+ frequently and the thought of a jumped chain at that speed terrifies you (it used to do me), in which case play safe.

Good advice, mush.

Just to add my two-penneth to the thread. The chain can be replaced without the sprockets but its hardly worth it in my experience (over 30 years, Jap, Brit, Yank and Italian machines). As an interim measure, if you're strapped for cash and the sprockets aren't excessively worn, changing the chain without the sprockets is ok so long as you keep a close eye on the sprockets from then on. Some chains can be bought 'off-the-roll' and work well for this job. However, I've found over the years that doing this can lead to losing a tooth - easy enough to see on the rear but not so on the front. This can make your chain slip off and lock your back wheel. Not too bad a low speed (which has happened to me) but I dread to think what it would be like if you were motoring along. Also, it never quite works out as a 2:1 ratio. For example, putting the new chain on the old sprockets increases the wear on the sprocket as they are (these days) often made from a soft alloy. So, you will need to change out the sprockets before the new chain is fully worn. I would never put an old chain on new sprockets. I always change both chain and sprockets at the same time. Buying the whole lot as a kit works better in my opinion and is more cost effective over the long term.

A quick tip...

As chains wear they become slack not just front to back but also side to side which increases the wear on the sprockets, so it's important to keep your chain properly adjusted and lubricated (where appropriate). As Mush says the sprockets will appear hooked through excessive wear (particularly if you're a bit heavy handed with the throttle, wheelies, fast starts, etc.) but I would say that, if your sprockets are hooked at all, they're past it because the new chain just won't sit right - again, as Mush says above. A seized link can also cause the chain to jump off so make sure you roll the chain through a couple of complete revolutions (on and off the stand) after fitting or adjusting and don't over-tighten.

And on chain vs belt vs shaft...

Belts are good because they require less routine maintenance but replacing them is a nause as the swing arm needs to come off and they are expensive. Shafts work well as long as they're kept well lubricated but if one fails, it's going to cost you. Great on a tourer but they never quite deliver the grunt that chains and belts do. I replaced the belt on my Harley with a chain because it's more versatile in my book and I ride every day so it works out more economical. It gives me more wheel options too, is easier for a road-side repair, and replacement is easier to fund when cash is short. The draw back being it takes more routine maintenance but I check my chain every few days and I've been doing it this way for so long that it only takes a few minutes to adjust.

Have always gone two chains to one sprocket set, good named brand lube as well,

Of course regular inspection and maintenance and ditching immediately if any damage.

No wanting to start a row but dislike shaft drives on bikes, no reason other than I do not like them. Also dislike large tourers (especially those goldwings with trailers) If you want to carry that much stuff buy a car.

Off topic slightly;

I last had a shatie in the early 80's - a XJ750. I got rid of it after 2 months as I couldn't get to grips with the torque rise and fall under acceleration / engine braking, especially in corners (I know it's bad riding style!!)

Does it still occurr on modern shafties?

RS,

Are you running a wider rear tyre than stock on your Harley? Which model is it? Just interested! Width of the belt is often a reason given for changing back to chain. Im not sure I can see the economy argument or how daily riding affects it. I know people with 75,000 miles or more on original final drive belts. I have had two that have gone to 30,000(ish) miles with no sign of trouble. A belt may be expensive if you have to replace it but, given that most people never will, its not really relevant!

Originally Posted by Blokeonabike

RS,

Are you running a wider rear tyre than stock on your Harley? Which model is it? Just interested! Width of the belt is often a reason given for changing back to chain. Im not sure I can see the economy argument or how daily riding affects it. I know people with 75,000 miles or more on original final drive belts. I have had two that have gone to 30,000(ish) miles with no sign of trouble. A belt may be expensive if you have to replace it but, given that most people never will, its not really relevant!

It's one of my own concoctions. I modified and FXR frame and slotted in a Road King motor and trans. I run it on Fatboy wheels and front end. I took the belt off so I could change the back wheel and tyre, etc., more easily. It twitches a bit in the rain. The rear is a solid with a 130 tyre but that's just not wide enough. So, the plan is to go up to about 150 (because that appears to be the limit for bias-belted). I've got an offset sprocket kit that's due to go on this week, if I can get time of work to do it. It's a bit of a work in progress because it gets used everyday - more or less. As far as economy goes, I find there are more OEM chains than belts out there so I can shop around. I can't afford dealer prices.

Originally Posted by mush_dad

Off topic slightly;

I last had a shatie in the early 80's - a XJ750. I got rid of it after 2 months as I couldn't get to grips with the torque rise and fall under acceleration / engine braking, especially in corners (I know it's bad riding style!!)

Does it still occurr on modern shafties?

I've had an XJ900 and an FJR1300, both fabulous bikes. The XJ900 is/was IMHO the ideal commuter/dispatch bike ever, the FJR a really accomplished sporty tourer. I never detected any of the legendary torque rise/fall, nor any drivetrain inefficiency whatsoever. On the other side, after messing around for years with chains, tensioners, Scottoilers and filthy black goo - I was blown away by bikes that needed no adjustments or major cleaning operations. If I buy another bike, it will definitely be a shaftie. In fact, I hope they bring back a simple big bike like the XJ900 - aircooled, not much plastic, really easy maintenance.