97 Magnum 425 backfiring

Ran good yesterday.Today it want crank and it's backfiring (sounds like a rifle shot)..just want start....Any suggestions!
It's a 1997 polaris 425 magnum 6x6

18 sportsman 850 on the way!

Hey guys, grew up riding, havent had a bike of any kids in a few years. Well I just pulled the trigger on an 18' sportman 850 (no PS) base model.

Super excited, as this bike.i will use all year round, for ice fishing as well in the winter. I'm located in southern/central ontario about an hour north of T.o. paid 9,150 before hst so I couldn't pass it up. I was looking at used junk for 6k , and I figured to finance a few grand and habe a brand new unbeaten bike was the route for me.

Guys I plan to buy some nice new tires and wheels. Ky question is what's a good tires size thats not to unreal, and a tire thats good for mud but I can still ride the road where I need to.

And what are some good bang for the buck mods? Exhaust? New CDI? Thanks guys!

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Want to add horn

Who makes the loudest horn? Do not want an air horn but all electric. To be mounted under the front hood. Want to use mainly when you may come up along side one of your bunch and you want them to stop. I want, need to get their attention.:eek