We are having a problem with the Polaris 500 - it runs backfires and then have to crank it again. On a cold start we have to choke it, small amount on the throttle and do it several times. It will eventually crank. Why is this so hard to crank?

The number 1 problem with ATVs is the carburetor. This could be a mixture problem... too rich will cause backfiring and difficulty starting as the carb needs more air. Try leaning it down a 1/8 turn. The choke is always intended to be used when starting; if you don't need to use the choke, the card is definitely running too rich. If you can't adjust to make it behave properly, then rebuild the carb, It's not difficult.. get a new throttle spring and float too. Ensure you place the keeper clip on the correct groove of the needle valve... where the throttle cable connects. Replace all the jets and gaskets... don;t get them mixed up. One larger jet is the primary jet and the smaller one, is the secondary. Get new screws, if the screws are a bit dog eared. Write down your previous mixture settings and start from there to adjust the mixture for starting and assure a slightly skipped idle. (Don't worry as you add throttle it will run smoothly.)