Hi, I have a 1987 Polaris Trailboss 250. The previous owner said it had an undersized battery, which didnt have enough juice to start it electrically but it ran fine with the pull start for the first couple days I had it. Then it got difficult, sometimes it would start in two or three pulls, and other times it wouldnt start no matter what I tried. Sparkplug is brand new and I was told it may be the CDI box but I was looking for a second opinion. Any thoughts what else it could be?

 

Check for spark and compression first! Will run with out a battery as it's the old magnetically triggered ignition system,but needs the battery for electric start,lights,etc. Old models first used the 14La2 battery,with the positive on the right side facing inward in the battery box.. Crappy idea. If have the room on the cables or if someone has changed the cables,use either a 14aa2 or a 14ah(maintenance free) battery.Once running regulator should be charging around 14 volts or so back to the battery.If compression is at least 120 psi or so and spark is ok and still doesn't want to run,check into the carb next. Plenty of cheap carb kits for these thing along with some aftermarket electrical items is needed.Plus leaking crank seals are another thing,but check these things out first.http://www.ebay.com/itm/Moose-Carburetor-Rebuild-Kit-10030004-Polaris-Trail-Boss-87-92-/181301055057?pt=Motors_ATV_Parts_Accessories&hash=item2a36628e51&vxp=mtr

 

Thankyou! That helps alot!