FCR 39 Jetting...

[Maryland 400EX]

My carb came from Sparks with a 165 Main Jet which worked perfectly for 50 degree weather. Now that it's in the mid 30's my EX feels like it lost some oomph in the mid and upper rpm ranges. My question to FCR owners is do you think that using a 168 or 170 main jet with just an X-6 Pipe and carb with no lid on the airbox is too much main? I don't have access to a 168 main but I do have a 170 in which I'll try tomorrow. The reason I'm asking is because I've seen guys with 440 motors using 165 main jets...

[Maryland 400EX]

I did a little research and found that another EX Rider (Methyman) uses a 170 main with basically the same setup that I have. I went to the site topozone.com to see what the difference in elevation was between me (Near DC) which was 40 feet and Methyman (Ft. Myers, Fla.) which happens to be a mere 10 feet. From what I can see it looks like I'll be okay with the 170 main jets and 30 degree weather. If the 170 works for him I suppose it'll do the same for me because I doubt it seriously if Methyman will ever see 30 degree weather where he is... I know there are lots of variables to consider when it comes to this stuff but an educated guess is what I'm looking for.

[stupid driver]

i still got the 165 in mine. its 30 degrees here at 1100 elevation. the plug was perfect the other night. i thnk that once i get in the real cold weather ill need a jett change tho