You definitely have a problem! I installed my current chain 24,000 miles ago. I have only had to make the slightest adjustments to it during that time, and those adjustments total only about 1/8 inch in 24,000 miles. I’ve owned my KZ650-C1 for nearly 41 years; personal experience tells me riding fast won’t cause the wear you describe.
So here are some possibilities –
1. You are adjusting the chain improperly. If you are not leaving the correct amount of slack in the chain it will stretch. It must. This is because when you adjust the chain the rear axle is below the imaginary extended line that would be drawn between the counter sprocket center and the swing arm pivot center. When you ride the bike the swing arm rises and that lengthens the distance between the counter sprocket center and the rear axle. If there is insufficient slack in the chain when this happens the chain will stretch or break. How do you measure chain slack when adjusting the chain?
2. When you replaced the chain you failed to replace both sprockets. The dimensions of the sprockets and chain must match. If one installs a new chain on used sprockets the chain will wear prematurely as it tries to match the pitch of the sprockets. Similarly, if one replaces the sprockets and not the chain the sprockets will wear prematurely for the same reason. When the chain was replaced were both sprockets also replaced?
3. You are not lubing the chain properly. If you do not use decent chain lube on the chain on a regular basis the chain and sprockets can wear. What chain lube do you use and how often do you lube the chain?
4. The chain is of dubious quality. Cheap chains wear out much earlier than high quality chains. Who made the chain, and what type is it (x-ring, o-ring, no-ring)?
Ed
1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)
