Clutch Drag On The Yfz 450. How To Spot The Problem?

I just recently bought another yfz 450 after mine got stolen.. its an 05.. i think it has a cam mod.. and an hmf exhaust.. the first day i got it.. i was soo eagr to ride the damn thing.. i jumped on it.. drove it around for a while.. it ran strong.. well then i drove threw some water.. unfortunately the airbox little plug wasnt even on the bike.. water and sand went all threw my airbox.. i took the yfz home... tore off the carb.. took it apart.. cleaned allll the sand out of the carb.. put it all back togeather.. and forgot how many turns to put the air/fuel mixture screw in.. (so maybe that has something to do with this) anyways.. i put it all back togeather.. fired up right away.. drove it around the block.. ran good.. i got it home .. and when i went too put it in nuetral.. it was Reallly rough.. took like 2 minutes to get in nuetral.. i shut the bike off.. and rode it later that day.. and it was fine.. (but it is backfireing and running kinda w00terty now) .. today i started it up.. and went for a ride.. after about.. 15 minutes.. it was like the clutch wasnt disengaging.. i mean i could pull out and everything.. but i couldnt even pull up a wheelie.. it was like.. the RPM's were reving up but the bike wouldnt go faster.. almost seemed like i was peeling out.. rode it too a friends house... (couldnt get it into nuetral) let the bike sit for like 2 hours... started it up... and it ran fine.. was able too doo wheelies and everything... but after about 15 minutes... the same w00ter... any suggestions?? ive searched all over the internet.. and all threw these forums.. no one seems too have had the same problem