craftsman lt1000 help

i have a craftsman lt1000 riding mower when i start it it revs up hi and back to low it does it all the time while the mower is running but when i drop the blade it dont seem to do it and it runs a little sluggish sometime it stalls on me i have changewd the fuel filter thinking it might help but it didnt

Can you answer this question? I have a black dog that won't hunt, what should I check first? This may sound stupid, but just like you don't know what kind of dog I have, I don't know what kind of engine you have or what you have tried so far. Please provide us with make, model and serials numbers, plus a little back ground about what you have tried and if any happened the last time you used it. You will get more help from us when you do this.

take the carb off and take it apart and clean it real good all the passages it sounds like its hunting and starving for fuel and 99.9 % of the time its a dirty carb