Okay, so here is the backstory. After a winter of sitting in Alaska, I was out riding my 2000 Sportsman 500, it was running great with no rough running or top end issues or anything. I left my fuel petcock on reserve so I ended up running completely out of gas. Towed it home, filled it up and it would not start. Plenty of cranking power, no start.

Thought maybe some sediment from the bottom of the gas tank may've gotten in the carb or something so I took the carb apart and replace the needle and the seat, checked the float and put the carb back on and replaced the spark plug. Last night, finally after a lot of electric and pull starting got the machine to idle however if I so much as breathed on the throttle it would just die. No sputtering or choking, just die. Also, if I turned the choke on, it would die as well. After a while of letting it idle, I could touch the throttle and bring the RPM's up a few hundred but then beyond that, it would die.

At this point, I am leaning towards a possible cam shaft/exhaust lobe failure but wanted to see if there were any other ideas out there. I did replace the spark plug and when I had it out I checked the spark, while it was anything but strong, there was a spark when contacted with the stator cover.

Is there anything I am missing that it could be besides the cams? I could always pull the valve cover off and take a look but would rather avoid even that if I can.

 

Very easy to spot if it's a worn exhaust cam lobe which it sounds like.Common problem,will crank and idle,die or back fire under throttle.Hopefully it's not.Here's one from another member. http://forums.atvconnection.com/pola...d-cam-pic.html

 

did you thoroughly clean the carb when you had it apart? Is there a fuel filter than needs replaced? It could be clogged jets also. Seems like a big coincidence the cam would go bad right when you ran out of gas.

 

So I re-dug into the carb with the hour I had this evening for it. I ended up unhooking all the fuel lines and making sure they were clean along with the filter that is in-line between the pump and carb. Some gunk came out so I thought I had found the problem. I put it all back together and started it. Same thing as before. Idle, but any throttle and it dies.

I figured I would let it just idle for a bit while I cleaned up the tools and such. Came back to it 5-10 minutes later and it revved up although it didn't seem to rev as high as it used to, but I was messing with the throttle cable, so that may be a bad adjustment on my end. I figured I would give it a test ride. Rode it down the road. The motor sounded ok although the punch and top end seemed a bit lacking. (though its hard to judge since I just ended a season of snow machining up here in Alaska and am used to that torque, along with the throttle cable adjustment) �� Brought it back and shut it off and started it up, though again it would not rev without dying just as before I took it for a ride.

Anyway, there is a rattle coming from the rear differential that wasn't there before. When it ran out of fuel, I jumped on another quad to go get the trailer and tow it home. Those who stayed with the quad (out of town friends) decided to tow the machine back while I was gone and brought it home and I noticed they had left it in gear towing it 2-3 miles home. Could this have damaged something? I guess I thought it was common sense to anyone that when you tow something, it should be in neutral. Also my low gear shift linkage is bent since they towed it and it won't go into Low now. :-/

May just be dropping this machine off at the dealer... Would testing the compression tell me anything? Trying to do everything I can before I tear I go about taking the valve cover off. Lots of broken and riveted plastic from the PO that is a pain to take off to gain access to it.

Edit: I just remembered. I did adjust the setting on the needle in the carb down one more click (4th notch) which if I think this through correctly would let too much fuel past...? ALSO probably worth mentioning now that I think of it. I had dropped it off with a friend who was going to work on it for me but didn't get around to much of it, did discover fuel in the oil after all this. Probably thin enough to trash the lobe.

 

Dropping the clip(raising the needle )will affect mainly mid to high range.Not that hard to pull the plastic needed and pull the 8 bolts holding the valve cover on.Quick visual inspection could tell a lot as far as it being a cam problem. Plus compression should be somewhere between 55-90 psi on average because of the compression release device. By the sound of it with other hands touching this machine, you need to have this machine gone over from front to back.

 

Cracked open the valve cover tonight and the lobe looked alright. Not great but rocker arms where moving when it passed by. I will try and get a video up. I did play some more with the spark plug and it doesn't seem like it is getting good spark at all. (Every other crank there is a faint spark arc'ing) Could a failed stator cause the same type of issues?

Also, after it idles and then dies, it takes quite a bit of coaxing to get it to start again. It does not just start up right away.

 

Valves set at .006 intake and exhaust.If you have weak spark,could be trash/dirt in the stator under the the recoil cover, especially around the pick up(pulse) coil. Could be similar to what this member experienced.Plus the white and red/white wires from the pick up coil should ohm out around 97 ohms + or - 20%. http://forums.atvconnection.com/pola...ml#post3155476

 

dont forget to meter your spark plug cap too. there's a resistor in there that goes bad over time.