help....

[phatcat]

hi everyone. fairly new to this biking game, bought a 2001 gz250 bout 3 months ago. was having a lot of problems with the engine running too high and not idling at steady pace. a few friends told me the carb is filthy and needed to be cleaned out. then had a spill a few weeks back. bi.ke was lying on its left side for bout two or three minutes, bent handlebars and fork seals started to leak. sent for repair, the guy in the shop told me he changed out the oil and the plugs, and cleaned the carb. about a week later, say maybe 80km of city riding, the engine starts to splutter and die. restarted after first time and drove another 6km, then died again. got it started but after about1.5km it died again, and wouldnt restart. had to get towed home. have gotten it to startsince but theres a serious lack of power, the engine cuts out after about ten feet, sometimes when i just put it in gear. any ideas where i should start? do you think i should change out the carb, or could this be as a result of the bike being crashed? btw, i have a feeling the mechanic i sent it too is a bit of a cowboy, and im not sure i want to take his word for it, as im kind of getting the impression he can tell im a beginner and is just trying to scam a few quid out of me.

any advice would be greatly appreciated

cheers!!