I have a 2000 400ex that runs great when the temp is above say 45. If it goes lower than that it will not start. I have not had the bike that long but it has good compression, good spark,new spark plug gapped correctly. I cleaned the pilot jet which is a 38. Not sure on the main. I need some help on setting up with the correct jets to run in the winter. I'm in eastern pa and am looking forward to doing some snow riding. The bike has a white brothers slip on, unfiltered with the airborne lid drilled with 4 holes. Any help is appreciated

 

First thing is adjust the valves. After that, winter riding I usually go up one size on the pilot, one or two on the main and see how a plug chop looks. I am in WNY, so similar temps.

 

I read a lot of people going up to a 42 pilot jet. What kind of adjustments to the car you need to do after adjusting and changing the main and pilot Jets