Steve has basically hit the nail on the head � sort the fuelling and make the twist grip less sensitive. All I would add is checking/sorting the final drive (chain, sprockets and cush drive).

It�s the simple things that make the most difference� Before attempting any of the mods suggested, make sure your bike is properly serviced, with a clean air filter, decent correctly gapped spark plug, the idle speed is correctly adjusted to 1400-1500rpm, the cush drive rubbers are in intact and free from excessive play and the chain has the correct slack and is (along with the sprockets) in good condition.

Here�s where to look for information about the mods�

Twist-grip mod: http://www.xt660.com/showthread.php?p=154983

Cush drive rubber mod: http://www.xt660.com/showthread.php?t=12422

Kev fuelling mod: http://www.xt660.com/showthread.php?t=11641

O2 controller: http://www.xt660.com/showthread.php?t=20381

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