95 polaris magnum 425 backfires/no electric start

[TheDOM]

Help, new to atv.  Polaris given to me.  Ran when got it.  Couple years later it backfires when it warms up.  Runs great cold!  Also starter won't even turn over.  Any direction would help.

[Mech]

So tell us what circumstances it backfires under.. wide open throttle, opening throttle, inttermittently when it's idling etc, and whether it's out the exhaust or aircleaner.

Have you checked or changed the sparkplug and fuel filter ? Both good first steps probably.

The starter.. is the battery charged, does the neutral light come on, do you need to hold the clutch in to start it perhaps ? Has it been going recently or has it been parked up ?

You need to be more explicit about the problems and the circumstances.

[TheDOM]

Well, for starters, yes have replaced spark plug.  Yes new fuel filter.  It backfires when you increase throttle. It backfires at exhaust joint at connection after engine and also tailpipe.  As far as stater is concerned it won't even try to turn motor over.  Just clicks.  Yes neutral light is on.  There is no clutch on a 425.  Its either forward, reverse, or neutral. 

[Mech]

Ok. So you say when you increase throttle.. so is this when you are already driving along, or just sitting revving it up ? And if you are driving it at the time, how much throttle do you reckon you are or can give it before it backfires ? Does it still backfire if you don't give it more than a quarter throttle say, or does it only do it when you are already over a quarter and getting nearer three-quarters or full..  We need to be quite explicit.  If you open the throttle slowly, is it better, or conversely, if you snap it open is it worse ? It sounds like in the carby or fuel supply, but we might be able to pinpoint it a bit better if you can really take notice of all these small details..  It's what mechanics do when they are road testing.. we don't just go for a blat, we try things, and take note.. hot/cold/always, lots of throttle or little, immediately we throttle or only after a few seconds, on the flat or only up a big hill or under a long load..

The starter.. you could try putting something like a screwdriver across the starter relay terminals(the two big ones), if you can find it. If that gets the starter going then it's the relay that's playing up. If bridging the starter relay doesn't make the starter spin, then it's a cable or the starter.

[Mech]

I'm assuming that when the relay clicks... the neutral light doesn't go dim does it ?.. That would be something you should mention if it did..  haha

The more details you can give us the better. I see an awful lot of expensive parts getting thrown at bikes in here to no avail, because of bad or no diagnosis.

[TheDOM]

It does the backfire after you let motor warm up.  When you start pressing throttle it starts.  So bought an 8th maybe?  Does this in neutral or in gear.  When in gear has no power at all.  Wont even move itself 2 inches on flat ground.  Have tried jumping terminals but nothing.  Yes neutral light goes out when it clicks

[Mech]

Oh... went back and I see it runs good cold.. good man.. bad me.

[Mech]

Oh ok.. In that case, being that bad, and only hot.. I am thinking it's an electrical fault perhaps afterall.. an electronic fault in fact. So if you stop the motor for about five minutes, so the engine's still hot/warm, does it still do it. How cold does it have to get before it comes right again. If you have headlights you could try turning them on and seeing if it fixes it.. A faulty battery or bad battery connection could cause the voltage regulator to give you those symptoms.. 

Which brings us to...

The fact the neutral light goes dim when you're starting means there is a flat/crook battery, or a bad connection.. or a seized starter motor. First check the battery water and charge it. Check it's terminals are clean and tight. If you have an electrical gauge check the voltage at rest and again with the motor running.. It should have about 12.6 at rest, and no more than 14.7 running. Then if you had some jumper cables you could try putting positive battery power straight to the starter and see if it cranks. If it doesn't it might be a shorted/seized starter, or a bad earth. You could put another jumper from the battery earth to the starter body and try the button, or the power straight to the starter.. Try one thing at a time till you figure out if it's one of those two cables causing the no start