Whilst not the silkiest of gearboxes, the XT's shouldn't clunk excessively when the engine is warm. If yours is excessively clunky then something isn't quite right and I think there is a clue in what you have revealed about your bike...

Now 800 miles in four years is not a lot - the motor (and gearbox) are hardly run in! Crucially when was the oil last changed? Never mind the miles, the actual date. How long has it been sitting in there? Do you even know if the right grade is in it? It is quite probable, with the bike having sat about doing nothing for a good part of its life, that the clutch plates are sticky, contaminated or even swollen causing clutch drag, in turn making the gear changes less than smooth.

First thing I'd do is (for the sake of �25) change the oil and filter and see if that improves things. Also check that the clutch is adjusted properly with not too much (or too little free play) so you know the plates are disengaging properly.

Whilst you're at it, check the chain tension and condition and cush drive/sprocket carrier for rotational play. Both these factors contribute to sloppy on/off drive and make it hard to change gear smoothly. Your chain may well have stiff links and tight spots through lack of use.

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