Guys I bought a KX100 for my daughter this spring and it ran great and burned its mixture great. Well now that its hot outside I think she is jetted too fat cause man it is making a freaking mess. My daughter came in and told me the bike was leaking oil.....I went out and ever spot oil could come out of the exaust it was. It also didn't want to stay idling. Do you guys think it needs rejetted for the warm weather?
2 Stroke Jetting questions.
- Thread starter Bryce R
- Start date
James
Staff member
Chokey has a couple good articles you may want to glance over.
https://www.dirtbikeaddicts.com/forum/content/215-jetting-2-stroke.html
https://www.dirtbikeaddicts.com/forum/content/214-pre-mix-ratio-101.html
https://www.dirtbikeaddicts.com/forum/content/215-jetting-2-stroke.html
https://www.dirtbikeaddicts.com/forum/content/214-pre-mix-ratio-101.html
Yes, generally with 2 strokes you need 3-4 jets for pilot and main, and usually you rejet for roughly every 15 degrees of temperature change, give or take a bit for humidity, from what you are saying it would seem you will need to go down 1-2 on the pilot, and 1-2 on the main, but make sure you do 1 change at a time starting with the pilot
I have had 2 KX100s, neither have ever required a re-jet for temp changes, elev is a different story. Is the trans oil getting low? maybe a seal went bad.
i would start with the air screw first. would turn it out but start with finding out where it is right now. Turn it all the way in and count the turns. Then turn it back out to where it was and the adjust a half a turn out at a time. But it should never be more than 2 full turns then you need to jet.
The density of the air is the critical parameter. Temperature does make a big difference between freezing and 100F the density varies by almost 15%. It's a big change. Here is a chart that can give the corrected density altitude. That same freezing to 100F is like changing altitude by 4500 feet. It gives you an idea of how much things change with temp and altitude.
The smaller the displacement the more critical the jetting. I can run my XR600 well away from optimum and still have enough torque to ride whatever. A smaller bike can't tolerate the loss nearly as well.
Here is a density altitude chart. First go up the "pressure altitude" to your riding altitude and then go over to the temperature. For example My summer riding at 10,000 feet and 80F is almost like 13,000 feet in standard conditions. A cold winter desert ride at 2500 feet and 40F is like 1000 feet in standard conditions.
The smaller the displacement the more critical the jetting. I can run my XR600 well away from optimum and still have enough torque to ride whatever. A smaller bike can't tolerate the loss nearly as well.
Here is a density altitude chart. First go up the "pressure altitude" to your riding altitude and then go over to the temperature. For example My summer riding at 10,000 feet and 80F is almost like 13,000 feet in standard conditions. A cold winter desert ride at 2500 feet and 40F is like 1000 feet in standard conditions.