Welcome on board mate.

I think you'll find any improvements you make to the suspension will have very positive effects - particularly living in Kazakhstan! It's a weak point, especially the shock, and on used bikes over 12-15K miles the shock spring will have passed its best (and it was made of cheese in the first place!)

The same goes with the fuelling - anything is an improvement. They run way too lean in standard trim and getting the air/fuel ratio somewhere down to into mid-13s:1 (from stock 14+:1) will make your riding experience much more pleasurable, better throttle response, broader spread of power, more low down grunt, cooler running and better economy. The best bit is you don't have to break the bank to achieve this either! Have a read these threads:

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

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

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