We have an AC 300, when the weather is cold it won't run. 40 degress and below it doesn't want to start. Replaced spark plug numerous times, still no luck. We're thinking of taking it back to the dealer since its under warranty, but i don't think they will help it. Maybe someone came fix the problem. Also, engine has been bored out and new piston put in.

 

The post right before yours may give you step in the right direction. The Link is here. The gentleman "ttaylor" suggest rejetting. Maybe that's a start.

I'm a little curious about your bore job. How did it go? Did your bike run better after the bore? How much did you bore?

EtherNut

 

Open the pilot a little, make sure you note the original position. I also changed my main jet slightly from a 130, to 135 ( this isn't an AC though, and mine ran adequitly when cold anyhow, but had lost some omph when it got cold. )

 

This bike had about 3000 miles on it when the motor started using some oil. We took it in and they tore the motor down and they found the cyclinder wall had scratches in it, the rings were worn down bad. They bored it out 20 thousandths over stock and put in and oversized piston. It runs good when it gets warmed up, but if its cold about 40 degress and below it takes all morning to get it started. We took it back to the dealer to let them look at it. Were on a first name basis there now.