Jump to content
Sign in to follow this  

Cold Weather & Jetting

Recommended Posts

I went for a ride this weekend and it was probably in the low 40's to 50 degrees all day. Man did my bike run crisp! Don't know if it is a coincidence but my bike was idling high too when I first started it, to the point I backed the idle screw off a bit. Other than the adjustment to the idle screw my carb was set up the same as my last ride 2 weeks prior in the same area only about 20 degress warmer. My question is, through jetting adjustments can I get this "cold weather performance" all of the time and if so where would I start, pilot ,needle or main? I have tried adjusting my air screw in the warmer weather in an effort to crispen the bike up with limited success,I am riding a 2005 YZ 250 it has been rejetted but I couldn't tell you what I am running until I tear into the carb.

Thanks in advance for any light you can shed on this topic.

Share this post


Link to post
Share on other sites
I went for a ride this weekend and it was probably in the low 40's to 50 degrees all day. Man did my bike run crisp! Don't know if it is a coincidence but my bike was idling high too when I first started it, to the point I backed the idle screw off a bit. Other than the adjustment to the idle screw my carb was set up the same as my last ride 2 weeks prior in the same area only about 20 degress warmer. My question is, through jetting adjustments can I get this "cold weather performance" all of the time and if so where would I start, pilot ,needle or main? I have tried adjusting my air screw in the warmer weather in an effort to crispen the bike up with limited success,I am riding a 2005 YZ 250 it has been rejetted but I couldn't tell you what I am running until I tear into the carb.

Thanks in advance for any light you can shed on this topic.

Raise your needle clip one position and turn your fuel screw in 1/8-1/4 turn.

JayC

Share this post


Link to post
Share on other sites
Raise your needle clip one position and turn your fuel screw in 1/8-1/4 turn.

JayC

Thanks for the help JayC !

No fuel screw, two strokes don't have one.

You have an air screw. Turning it in cuts off the air, turning it out increases the air.

As the weather cools, the air cools, and compresses. Therefore there is more oxygen content in cold air than hot, for the same volume.

Thus, as the temperature decreases, your bike with run leaner.

Most bikes are jetted on the rich side, so when the temps drop, performance is gained.

Go to the yz 2stroke section and read up about jetting. Without knowing what your current settings are, the way it is running, it is impossible to make a suggestion where to go with your jets.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×