400EX??? you can try jetting it for the cold the 400's are extremely tempermental when it come to the cold weather, anyone up here with them will agree.
What I recomend is to simple set the choke to half pump the throttle 4 or 5 good pumps and barly I mean BARELY hold the throttle and start it when it starts keep that throttle position for about 2 or 3 min gradually turning off the choke after about 5 or so min you should be able to ride.
Haha yeah its my brothers it will turn over for ever and just will not fire. When u take out the spark plug its barely sparking at all like the cutest little spark u ever did see! Could anything cause that?
I dunno if it starts good in the summer we got it this winter and they had the thing all f'ed up so i had 2 change alot of things. But we got it cheap cuz the ppl thought it was the rings were fried. They just had a drilled out jet that was like a garden hose basically. Why are ppl so dumb?
Yeah we just have 2 hook it up to a battery charger because it will kill the battery 10 times before it will even fire. Then once its going we gotta baby sit it for like 20 minutes cuz it will occasionally die out. Then u can ride it and once its going its fine.
Low battery voltage will cause a weak spark. Like i said try putting a heat lamp or a lightbulb close the the battery area. Our boomlifts have a sleeve that slips over the battery and you plug it in to keep the battery warm. you loose cranking amps during cold months and if you have a weak cell it drops off even more.