Heres a cut & paste from another forum, not all relevent but you can pick out bits that help;
You don't say where the "play" is, approx 2" rotational backlash at the edge of the rear tyre whilst in 1st gear is normal, you could try to narrow down the problem by the following,
Check the rear wheel bolts are correctly tightened! (It does happen!)
Bike on center-stand and in 1st, grip wheel at 12 & 6 o'clock position and feel for movement, if present likely to be F/Drive issue,
Another test, Spin the wheel in neutral with a long screwdriver to the f/Drive casing and your ear, the graunching will be unmistakable.
To test the swinging arm bearings and or pararlever pivot, apply rear brake and try and feel movement by pushing / pulling the rear wheel from the offside at the 9 o'clock position.
Another test, drain F/D oil and inspect for debris.
To check for shaft, U/J problems, again bike on center stand in 1st and move the wheel in a rotational way, as above, there will be about 2" of backlash measured at the edge of the rear tyre in a sound setup.
If it turns out to be a F/D problem or a drive shaft problem and you don't want to do it yourself, remove it and get it to Steve at Scriminger Engineering, As a happy customer I can highly recommend him.
http://www.scriminger.co.uk/
Do search for " Paralever Play " for lots more info
Why couldn't I find that....
