50 predator was running fine all season..... but sputtered and quit running late fall 2010. Left it until this spring to look at. Spring time came... tried to start and would seem to wanna run but would sputter and stop. Seems to have good cylinder compression ..approx 135-140 psi and holds pressure at 125 for a bit then drops to about 85 and holds there for a minute or so. Changed the spark plug....no luck. I removed in-line fuel filter and tried without it...tank vent checked & not clogged.... fuel lines not kinked... Was told by 2 dealerships originally that I wouldn't need a carb kit...just a good cleaning should do the trick. removed carb float bowl, float and needle and fuel tank then cleaned and filled tank with new fuel.... Seemed to wanna run again briefly then sputtered and stopped. Squirted fuel into cylinder or carb inlet and would seem to again wanna run briefly then stop. Removed entire carb this time and removed jets then cleaned thoroughly with carb clean aerosal....back together and seemed again to wanna start up but no luck running. Opened carb float bowl drain plug to check for fuel in bowl ...Yes...Checked new spark plug for spark...seemed weak and intermittent.... changed with another new spark plug..... Quad started right away and idled and seemed to even rev when throttle depressed. Shut off and started again to make sure it ran again before finishing the rest of quad assembly. Idled fine again but sputtered when throttle depressed this time and then stalled...started a few more short times and then right back to sputtered starts and not running.
Plug to wire connection? plug wire/coil? Over fueling? not enough fuel? Am gonna remove the carb one more time this weekend to make sure of float buoyancy and needle operation and cleanliness.... gonna soak carb in cleaner overnight. Throttle barrel adjustment? Choke barrel adjustment?
Should I also check the intake reeds? but seems to have decent compression. HELP !!

 

The stator is the most common thing to go out on the little ones! #0451000 is the part number. Sounds like you've done ALL you can do on the fuel system! I replaced quite a few especially on the earlier ones and the stator hasn't changed even on the 2005 model. Can cause intermittent spark or weak spark. Could be the cdi,but I really doubt it. I've posted before that I couldn't remember if I ever had to change a cdi or coil,usually just the stators! BUT I would ask the dealer on the stator resistance specs on the white and white/red wire(trigger coil) plus on the back/red and red wires(if I remember correctly) Stators were a little over a 120 dollars when I retired,IF this is the problem! Good luck OPT

 

I just ran into the same exact problem with my kids quad. Spark was weak and intermittent. After checking everything here is what I found. The spark plug wire has a rubber boot that sits on against the head when over the plug. The boot was conducting spark and grounding against the head. I saw this by cranking it in the dark. The boot slips off the end and your left with the plastic plug connector. Try removing the boot. My boot was clean and dry with no cracks. Don't know why it conducted spark but it did. Good luck!

 

Old post I know, but, I'm sure people will find this post months, years later (like I did...) I just had the same issue. And the spark plug wire and boot just about zapped me when I touched it when it was running (even though nothing was frayed or "exposed." So, I used electrical tape to seal that end of the spark plug wire, trimmed the flared portion of the spark plug boot so it won't touch the cylinder head, I also screwed that end of the spark plug connector into the plug wire better. It seemed to help. I have no idea why though. But after doing this - my 2005 Polaris Predator 50 fired right up and ran fine. Very strange, because, it had run fine even the day before, (was doing all sorts of maintenance and whatnot with the body off, ran perfectly - but when I put the body back on, put EVERYTHING back together to get it ready for use, it would crank, run for a few seconds, then die. Crank, run a few seconds, die. (full tank of fresh good fuel, new spark plug, everything was perfect) I was like what in the heck is going on when it was perfect just hours before. Well, the spark plug boot thing is real, and I saw no damage to it, nothing "exposed", nothing amiss that I could see (been a home mechanic for more than 30 years). Looked perfectly normal. My mod seemed to fix it though. Makes no sense, but whatever. Many things in life make no sense.

Dave
Atlanta GA

 

Same issue here. Took the carb apart and cleaned everything. It will start and stay running if I shove a shop rag into the air intake hole. But the second I remove it, it dies. What's going on?