There could be a lot of reasons but start with the basics.
Check that the air filter is not dirty/blocked.
Check that the fuel tank is free from dirt or droplets of water in the fuel.
If your machine has any rubber/plastic fuel lines check for cracks (where air can get drawn in).
If it has an inline fuel filter check this is not blocked.
Remove sparkplug and clean if fouled/dirty.
Note: some types of air filter dont have to look bunged up to be blocked. Try removing filter element and run engine. If it stays running this points to the filter being blocked. Refit the filter and see if the problem returns. Replace filter if required.
WARNING do not run engine for a prolonged time without a filter as engine damage can occure.
If these steps dont cure your problem a trip to your local repair centre may be required.
smudge, November 2008
