I'm looking for a bit of help so I can help my father in law with his ATP.

We were up hunting this weekend and his ATP would start coughing and back firing and would quit, It seemed to do it especially on the longer climbs up some long rough trails.
Let it sit for a few min, pull choke crank and crank and it would start and run.
It did this 3 or 4 times. It really seems to me to be a fuel problem.

When we were ready to leave it had been sitting all night and it was fairly cold, It started right up and seemed to run fine. I loaded it on the trailer with no problem, got home and rode around a bit, seemed fine.

 

My 600 twin did the same sort of thing last weekend too. I took the air filter off and checked for cracked rubber by the carb. Ended up spittering and sputtering many times. Tapped on the carb a few times. Shut it off and restarted many times and then it all just went away. My thought is that either the needle in the carb was stuck or something needed to work its way thru. Has run perfect ever since without doing anything else...damn gremlins!!!

 

I hated Gremlins too... Both kinds

 

Could it be a fuel filter that would cause this sort of trouble or should I start with the carb?

 

If it's running good now I wouldn't mess with it.. If you want to you can check the easy stuff such as fuel supply to the carb,air filter,drain the carb bowl,etc.. Pull the fuel line at the carb and crank the engine over. Should be a steady pulse of fuel from the line. If not,could be a fuel filter or even a weak fuel pump.If you even plan on going into the carb,always install a new carb kit. Not worth having to go back in twice as just cleaning one doesn't always solve problems. Just drive it around some more and try to duplicate driving conditions when it started running bad. If it runs ok,then just chalk it up to gremlins as Big600twin suggested..

 

I for sure want to make sure this problem is taken care of. I don't want to chance my father in law being left on the side of the mountain some place.
He has some mobility issues from an accident several yrs ago.

The machine acted up several times, it would bog out fart and pop and die. we had to drag it to camp the last time.
after waiting 10- 15 min you could full choke, crank and crank and it would finally start again. after that It would clear its lungs and then run fine for awhile, you could shut it off and it would start right up.

would cheap cycle parts be the place to order a carb kit? or just go to the stealer?

 

Usually cheapest place is ebay. Atp 500 takes the same kit as the Sportsman 500. http://www.ebay.com/itm/CARB-REBUILD-REPAIR-KIT-POLARIS-SPORTSMAN-500-2003-2004-2005-03-04-05-/230385051279?pt=Motors_ATV_Parts_Accessories&hash=item35a404e68f&vxp=mtr