Just bought this 2003 raptor 660R. It didn't crank when I bought it so I put a new starter on it along with cleaning the carburetor, new petcock, and a new solenoid. After the new parts I fired it up and it cranked. It idles as well and doesn't sound like anything is wrong with it. No smoke or nothing while idling. I went to press the throttle to hear it roar and it makes loud pops, sort of bogs down, and shoots out smoke. I've never seen anything like it. Not sure what it is or how to fix it so I'm hoping someone on this forum would have a good idea. Here's a video so you can see and hear what it's doing:

 

I assume you put fresh gas in the tank when you got it? white smoke is usually water, i wouldnt know the problem for sure but im waiting in on someone who will because im curious now

 

No I didn't put fresh gas in. I'll drain the tank and put some fresh 93 octane in and see if that fixes it! Thanks for the reply!

 

Tried what you said and I dumped out the old gas and put in some new fresh gas. Cranked it up and it smoked a ton, even more than before and I didn't even press the throttle. I just let it idle.

 

Have you gauged...changed the oil? May be over filled....or may have a blown head gasket.

 

I suspected a blown head gasket but I checked the coolant level and it was filled completely to the rim. Plus that wouldn't explain the popping

 

Yes, you can get popping and poor running like that from water in the fuel. First I would ask if you drained the carbs too. Water will be in the float bowls of those carbs if it was in the tank. Bad head gasket, well it doesn't take a lot of water to make them run poorly...

 

Yeah i drained everything. I'm about to check all my fluids to see if anything is low so I can see if it might be burning something.

 

I'm tired of dealing with it. First person to bring me $1000 gets it. I don't even want to look at it anymore.

 

dont give up lol, im thinking buddy that had it before you probably mud bogged it and got water in the engine, try draining the oil and put new oil in, do that 3 times so it flushes all the water out, like buddy said above^ it wont take much water to make it run poorly.
goodluck!