Help !!!!!! Jetting

[Quad18star]

Pappy could prolly answer this question for me very quickly . It's -3F right now and the YFZ450 has stock jetting . What should I run????

[LTandRaptorider]

I'm not familiar with the YFZ jetting, but since cold air is denser, you'll need to richen probably both the pilot and main jets by 1-2 sizes. The bigger concern of course is the main jet.

[86350x]

I think the rule of thumb is every 15 degrees equals one size larger, or smaller from cold to hot. Lol, I think us northern boys would be changing our jetting constantly though. Slapp in a 180 and see how it runs in this cold b.s.