I mentioned that the MoT tester had advisoried me that the drive chain was well buggered on the XT. He was not wrong. Here is one end of the old chain next to the new:
It's a full inch shorter, which translates to about 1.5% of the total length. The manual says the chain is dead when it becomes longer then the original by ... 1.5%. It is sloppy and full of tight spots, so it definitely needed doing.
The gearbox sprocket was badly worn too:
New one on the left, old one on the right. The teeth were getting badly hooked. I'm glad he told me about it when he did, as I don't think I would have given it a proper inspection for a while. After all, it's only 4500 miles since the old one was new.
I have been wondering why the set has only lasted as long as this. Many people get 20-30,000 miles out of a chain, and even with a big thudding single I don't see why it shouldn't have lasted for 15,000 or so. It was lubed every week until I fitted the Scottoiler, although I admit that otherwise it was neglected. As the sprocket is as badly worn as the chain, I don't think I can blame a poor quality chain. (The rear sprocket showed no signs of wear, but then it has three times the number of teeth as the front, so it lives an easier life.)
There's a new set on there now. Let's hope this one lasts a bit better. Some family turned up just as I was finishing off, so I didn't get the chance to give it a test ride. I am looking forward to that, though. The last time I replaced the chain, it was like having a new bike.