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When do you change your chain?


Change it when it's 2% longer than it was new. Assuming a 5/8" pitch chain (#520, 528, 530, 50, etc.), the length of ten full links pin to pin should be 6.25", 20 links, 12.5". Two percent over each of these would be 6.375" (6 3/8") and 12.75" (12 3/4"). The chain must be drawn taught when measuring, which is easily accomplished by placing a piece of wood or a tool handle between the chain and sprocket and rolling it under the chain to tighten it.

Another very accurate means of measuring the chain is to use a typical 6-7" vernier caliper on a 10 link section as shown in the attachment. Measure from one roller surface to the 11th one, and measure several sections. Compensating for the .400" roller diameter, the new length of the chain measured this way is 5.85", and 2% over is 6.0".

Once the chain is that much longer than spec, it starts chewing on the teeth of the sprockets. New sprockets can be installed without replacing the chain so long as it is 1% or less longer than new without any kind of problem.

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Not only does a worn out chain eat up sprockets it eats up horsepower as well, up to 10%.

Adjust your chain normally and then fully compress the suspension and check the chain free play, if it is tighter than it was with the suspension unloaded then you need to make chain adjustments with the suspenssion loaded, your chain will last longer.

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2% is unusually large. I am finding 0.6% and 0.8% to be more common. What is the source of this number please?

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You countershaft sprocket is the one which ruins your chain,because of a lot of dirt and the little radius,the power impact on the chain.

If you keep an eye on your CS sprocket and replace that early,you can safe your chain and rear sprocket.I wish ALL dirt bikes(not only the trials bikes) had from the factory a automatic chain tensioner.I have them mounted on all of my dirt bikes for many years and have very little chain waer . PIC one on my Zunny right behind the swingarm ,and pic 2 on my OSSA 1971 just a HD rubberband and a roller and it made it all trough the ISDT without tightening the chaine.

Hybrid 2014 002.jpg


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When the rear sprocket starts to fishhook the teeth.

I have a 2011 SUZ DR650SE, 50k mostly street miles.  My original chain/sprockets lasted just short of 25k miles, but then again, I cleaned it with kerosene and lubed it with chain wax every 600 miles as instructed by the service manual. It saw very little dirt during it's life, and when it did, it was mostly sand, but I cleaned/lubed it right after riding/before riding it again. I also changed the countershaft sprocket whenever it started to look even a little worn, which was often.  So, I think the key to chain/sprocket life is very frequent maintenance and avoiding harsh environments when possible.

I probably could have ridden the original chain/sprockets further, but once the rear sprocket teeth started to fishhook, I figured I had gotten my money's worth and changed it all out... both sprockets, and chain.

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