how much difference does temperature make on jetting adjustment?

[125rmcrazy]

my buddy got a 94 rm 125 and hes just brought it up from down south and its been jetted for warm temps, 0-2000ft. he is running a 300 mainjet. where i live now the temperatures are below freezing but we decided to go for a ride. my buddys bike started acting weird, eng seemed to run and rev excellent, but no power and sometimes a stutter before it would rev. im thinking the mixture is just way lean but he argued with me it was somitng to do with his ignition? the stock size jet in the owners manual is 330. and thats at 60 degrees. any thoughts?

 

[AwfulSmokey]

The difference in temps would definitely require re-jetting.

 

[jason33]

too lean - is too lean
you want a tan color no matter what temp it is out side-
things do not keep from getting done in alaska- and other freezing areas of the world

 

[makyz125]

Going from 70 to 40 degrees on my '06 YZ125 required a step larger in the pilot and main jets. Better safe than sorry.

 

[whenfoxforks-ruled]

10 to 20 degrees Fahrenheit require adjustments to the carb. Celsius, 5 to 10? You are pretty lean.