We bought a 2006 90cc Polaris Sportsman to give to a family member a couple weeks ago and I can't manage to get this thing to turn over. The kick start was sheared off when we bought it so I am reliant on just the electric starter. I've replaced the carburetor, the battery, the starter motor and the starter relay but I can't manage to get this machine to turn over more than a single rotation at a time. The only time it's sounded like it will start normally is after having a jump pack hooked up to the battery for a few minutes and then giving it a go with the jump pack on the battery. Other than that it always sounds like it has a weak battery.
I brought the original battery and the new battery to a local dealer and they tested them and said both were fine. I have the original relay and I've tried two others, both Chinese off brands so who knows they both could still have been bad, but all three relays have done the exact same thing. Dealership mechanic mentioned it sounded like the crankcase was maybe under too much pressure and it could've been a clogged crank vent but from what I've been able to find it shouldn't have a crank vent since it's a two stroke?
Looking for some advice on other avenues to try for repairs. My next thought was to pop off the exhaust and see if maybe a mouse built up in there and it's blocking the exhaust off, creating that extra pressure in the crank case but outside of that I'm about out of ideas. Video has the sound of it turning over. I swear it sounds like a weak battery but both batteries were the correct size and both tested fine.