30 amp main fuse blows when the key is turned on.

Can be "nasty problem, for it can mean DEATH, if as you attempt traffic manouvre & it blows !-(As safety precaution , & this TIP would be useful to most all Bikers>Call to friendly POLARIS ATV Dealer & ask for Automatic Re Settable 20 AMP PROTECTOR ( tHIS FITS THE 500 sPORTSMAN A T V & as far back as the 350L 2 Cycle Firebreathing A T V ()Standard Equipment )-Wire that in from POSITIVE Supply on to your loom, & attch its earth ( Negative cable to NEGATIVE > - on Your Battery!--That done, procede to your RecRegulator Unit &Examine Likely "Melting of Delrin (Nyloc, White looking plastic connector plug to terminals of Rectifier/Regulator , Test Output from Alternator., Ensure ALL Eaths have been attended properly, by Unscrewing, & Shining through the Paintwork Refit, tighten & Apply Silicone Sealant ( So that when You "Power Clean" the Motorcycle You wont be "Degrading the EARTHS again!--Now Ride!--If the Loom Loom, near steering head happens to "Short out" The POLARIS Re Settable Fuse Link & Sealed in waterproof covering, will Re Set & then You get chance to further investigate at Your workshop!!Arm yourself with Voltohmyst , or Multimeter OOR mini pointer that can sense Current Flowing, check out ALL Swithes ( Disconnect rear brake light switch & front one by way of unplugging supply leads ( Just possible that You have intermittant short in one of them!--Did You happen to note IF You were turning slightly to Left or Right when Fuse Blew?--Well, look then for "Stress areas for wiring looms, as at Steering Head Stem region, Open the Sheath with Razor Blade & attempt to pull wires apart slightly , then EXAMINE RFOR>bare leads !---With Multimeter You could slowly "ISOLATE" components & IF You had reference to WIRING CHART You then could Painstakingly TRACE EACK LEAD & ENSURE it has no "LEAKAGE "--Best Of Luck & "StayUpright" -Des.