Cold start the other day and it fired up and died. Cranked and cranked and nothing. Let it sit 20 min. and got it to fire up and I kept on the throttle to keep it going. It`s been this way since I`ve had it and worse the colder it gets. I try full choke, no choke, open throttle etc. and it doesn`t fire. Let it sit and it fires up. It does the same if it`s been warmed up and let sitting for 20 min. If I get on the throttle I can keep it going. If it stalls it`s all over.

This weekend I think I`ll try giving it a shot of starting fluid to confirm it`s carb related. I`m sure it is but don`t know how the carb can act up like this. Once I get it warmed up a little I plow with it.

 

Just checking,do you have only 1/8" slack at the throttle lever? Plus have you checked that the tank vent line is open and not kinked? It can cause one to stall out from a vapor lock condition. Plus have you installed a carb kit or cleaned the carb or checked for tight valves? Could be this or even an electrical problem as it gets warm. Just eliminate one thing at a time,such as checking the valves first,fuel supply from the pump next,then the carb,etc. If none of this helps you may need to look at the schematic in your manual to check resistance on the stator,pulse coil and ignition coil,plug wire and cap.Any of these components can be weak or fail as the machine warms up mimicking a carb problem.

 

I will be doing all the above in spring. Just trying to make sense of it. Gotta plow yet this year and it`s ok if I just blip the throttle right away. I don`t think there`s free play in the throttle so will address that and get back to ya. Thanx

 

Try this . Click on the top bar not main body.

http://www.ehow.com/video_4468404_polaris-atv-thumb-throttle-maintenance.html

 

Just checked and the throttle has the recommended free play. Was hoping it to be that simple. I`m good at getting Harley`s and airplanes started. With them you can prime with fuel by pumping the throttle or primer. Can`t do anything on this but crank. Using full choke or no choke doesn`t give results on the Sportsman either. When it starts it doesn`t act lean or flooded.

 

Best thing I can tell you is to eliminate one area at a time as you have on the throttle play.Once you eliminate a fuel problem or the carb,move on. Could even be something simple as a spark plug partially fouled, short on the plug wire,split plug cap that may be touching metal or something else that's been starring you in the face. That's how I had to do on a lot of machines,just a process of elimination. Check one thing off the list and move on to the next until you find the problem.

 

If it were mine, I'd adjust the fuel screw on the carb.

 

Thought I`d share this. Clears up what`s involved. Might check my carb this weekend depending on wx.

Can carb be removed without taking off tank and cab?

 

Good video on the BST 40,but leaves out one of the most important parts and that's the float level adjustment. Does explain how critical the spring has to fit in the diaphragm assembly and cap. Air box lid needs to be on if you adjust the fuel mixture screw to get a smoother idle. I just popped the side panels off, unbolted the fuel tank and propped the back of the tank up with a large socket. Gives you room to work.Tank doesn't have to be removed and neither does the throttle cable. The wire spring on the bottom of the carb is a weak link as it always breaks leaving the idle adjuster laying on the starter. When this happened I just used a thin plastic covered metal tab that's on most dirt bikes holding vent lines in place. I just used it in place of the wire holder and wrapped it around the idle adjuster under the carb and no more problems. A small "baby" pair of pliers works great on removing stubborn screws on the carb bowl instead of a phillips screw driver on the soft head screws.You can even replace these with metric allen head bolts if you wish. http://www.ebay.com/itm/New-Snap-On-Straight-Serrated-Jaws-Adjustable-Joint-Pliers-4-3-4-AWP45-USA-/321320075845?pt=Motors_Automotive_Tools&hash=item4ad02b4245&vxp=mtr

 

I replaced the spark plug with correct part. Had a champion rc12yc. Never gave it thought before as it ran good once going. Now it runs even better and starts and runs. The parts man gave me the champion chart and it would cross to a 9 heat range. The 12 is 3 ranges colder. I put in an NGK BKR6E as the service manual lists at .036" gap. I gapped it at .034". Tomorrow will be the test. I`m not going to pre-heat it and we are supposed to get snow, so will see how it starts and runs.