New Drive Belt is not aligning correctly and is moving inboard against the engine case when you rotate the wheel forward. I have just replaced the belt on the M2 by lifting the frame up off the engine etc. and replaced the rear isolators. I thought I may have misaligned the engine and frame. But the belt must have been touching the engine case previously because there is wear on the engine case already.
could it be something else, like swingarm bearings? I couldn't feel any play. The belt lasted 23,500 miles.
Any thoughts would be very welcome.
Doug

Is the rear wheel aligned?

The isolators will not have an effect as the swinging arm is bolted to the engine, the isolators will change the alignment if the frame only.

The belt will run one way or the other depending on which direction the rear wheel is rotated...

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08 Specialized Langster

Thanks Pash.
The belt does run towards the engine case when the bike is moved forward.
So the belt will never run exactly in the centre of the pulleys, even when I have aligned the wheels?

Yeah if you do it perfectly.

What happens if you roll the bike backwards?

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08 Specialized Langster

I had the same issue when I put the last belt on the M2.

I had significant wear on the front pulley, and where the belt sits has worn a deeper groove, so there was a sharp lip on the inside of the pulley as well, which didn't stop the belt from going over it, but stopped it from going back.

After advice that it would sort itself out over time, I watched it not sort itself out for a few days, while starting to chew the gearbox-side of the belt out.

I ended up bending a very simple metal guide, that I bolted to the gearbox/swingarm bolting point, which just "encouraged" the belt to stay in the correct place until it had settled down. Took less than a week for the belt to get into the right place, and it being kept in place by a bit of smooth alloy didn't do any damage at all to the belt, as opposed to letting it run on the side of the gearbox.

Left the thing on from then afterwards, and it went with the bike. Genuine Fowlerware alloy (from a toilet cistern...)

When the bike is rolled backwards the belt tracks to the outer edge of the front pulley.
There is a slight lip on the inside edge of the pulley.
Thanks for the idea on the belt guide that's going to be my plan 'B'.
Cheers
Doug