Polaris 600 RMK carb- idles up and down

[indy5xc]

Hi, Greg here. I have a 2008 RMK 600 carbed twin 2-stroke, which I replaced the stator this past spring, 2015. The spark dropped off when I shut down the sled last season, no spark. Eventually ohm'ed out the stator and knew it was the cause. After replacing the stator, and simply putting the stock timing mark on the crankcase starting point triangle indication, it started and ran fine. I put it on the trailer and brought it back to camp for summer storage after a quick 1 minute grass drag. When I went to remove it from the trailer, I forgot to turn the fuel back on- when it ran out of gas warming up, I turned the fuel on, it fired up, but here's where it gets tricky. It surges between 1500rpm and 400-500rpm. If I hit the throttle it bogs. If I hit the perc reverse button, it tries to stall/start in reverse. If I hold the reverse button in, it idles normally at 1500RPM? I got it to go into reverse and held the perc button in, and it drove off the trailer. I hit the perc, and it goes back to surging 500-1500rpm? If I again hold perc button, it idles and rides normally? I asked Dan's Polaris what they thought- they suggested trying a known good left-hand control with the perc pushbutton on it? My friends sled is a 2008 700 EFI and I can try that, but don't know if it's the same- and ideas? I'm going up Friday to troubleshoot the left-hand switch control, to see if it's a loose connection. Hope it's an easy fix- will check all connections.
Thanks for any suggestions. I don't like the service manual I have on my computer, PDF version. It does talk about an Electronic Wrench tool (software with some sort of code reader I presume?) Glad I still have my recently rebuilt 700 xcsp to ride. Greg

 

[retiredpop]

Just running out of gas shouldn't cause it. The reverse button appears to remove a ground from pin 7 of the CDI when pushed in. I'm not sure what happens after that to get the engine to reverse. It's kind of strange that the idle goes to normal steady when you hold it. Maybe it does something to the timing so that is why it runs normal. There is a timing procedure but you need a dial indicator gauge to do it in order to mark the flywheel although the timing marks should have been close enough. Just another thought is have you flipped the choke on when it is surging to see what that does?

The engine should have cycled back and forth between high altitude setting and low altitude setting when you pushed and held the reverse button. Did you happen to notice if the reverse indicator light was blinking faster at times and then slower after holding in the reverse button and vice versa?

 

[indy5xc]

Mystery solved

I went back and tried restarting the sled, after sitting all summer in storage, and of course, it idled fine. I had bought a new switch assembly and realized they are made in India? The problem may have been a bad switch assembly, meaning there are 2 small ground points that should make contact with the handlebars-my assembly is a little loose and can rotate with 10-20 pounds spin force, so it may have been wet, or rusty on the bars, and when I went to start it I first spun it a inch back and forth to possibly make contact? Nevertheless, I kept the new $65 switch assy in case the problem returns, at least I can eliminate that.
Thanks for your post! When in doubt, throttle out!

 

[MARV1]

For better fuel economy:
40 pilots
Needles dropped to #2
400 mains if 10* and above

 

[rydrhard]

Greg, that's interesting. I'm having the same problem. Did your bogging issue go away? My reverse issue went away after replacing my voltage regulator, but the mid range and full throttle bogging is still there. Leo

 

[retiredpop]

Greg, that's interesting. I'm having the same problem. Did your bogging issue go away? My reverse issue went away after replacing my voltage regulator, but the mid range and full throttle bogging is still there. Leo

First thing I would so is clean the carbs if you did not put some kind of fuel stabilizer in the fuel before storage last spring and the run it long enough to get the stabilized gas into the carbs.

Secondly, did you drain all the old fuel out of the tank and replace with fresh? Even with fuel stabilizer the fuel still deteriorates in octane.

If the sled was stored outside is there a mouse nest in the air box or exhaust?