Got a 2006 polaris 500 ho efi,i have low voltage at the speedo head on the red/white wire, 4.5 volts.red/whit wire feeds lots of stuff.If i jump the red/white and red wire at the speedo the dash will come on,but still won't crank. I have 12 volts on the solid red wire at the speedo, lights are dim,does the voltage regulater supply the voltage to the assessories.starter wont crank,you can jump the solenoid and crank it.

SOURCE: 2007 POLARIS SPORTSMAN X2 H.O. got this polaris

Try unhooking the battery for an hour then rehook and try it

SOURCE: Service manual for a 2006 500 Polaris Sportsman HO

I have a 2006 Sportstman 500HO ATV, EFI. Sometimes it will run 100% correct, other times it will start, idle fine but then when giving it throttle will will start to surge almost like it's hitting a rev limited. Sometimes it will backfire and stall. I already replaced fuel filter, flushed the fuel lines and gave it fresh gas and installed a new spark plug, but no good. I also checked the throttle switch and it's not making contact to stall it. I download the service manaul and tested each sensor and they tested fine which is probablt why I get no check engine light.
This ATV is mainly used to plow snow in my driveway, no salt. It's used around my property but very lightly. It's still as clean as it was when I bought it and it doesn't have but about 40 hours on it.
Polaris 500 HO EFI 4x4 ATV: Vin# 4XAMH50A56B707664 purchased 6-8-2006

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SOURCE: polaris 2005 sportsman 500 H.O. service manual

Downloaded this last week....its the factory service manual ($3.99)

http://www.tradebit.com/filedetail.php/6901881-download-now-polaris-sportsman-500-2005-05

SOURCE: Need user manual for polaris 800 EFI

I found a Polaris Sportsman 80 repair manual. Clymer just came out with that service manual. You can get it at The Manual Store:

SOURCE: 2007 Polaris Ranger 500 EFI

If your battery is good then you have dirty or loose connections at the battery or the starter. Quite often this will be on the ground side.