on sunday i took my quad out to el mirage it ran great for about an hour but then it started to bog and hesitate so i check on my plugs and they are completely black im running a hmf pipe and uni filter with a 175 maint jet and a 45 pilot jet the elevation was 2800-3800 to its highest point am i running a the correct jetting for this elevation.


jonathan

 

anybody also does the order of the spark plug wires matter or are they numbered.

 

I haven't re-jetted many ATV carbs but I have done a lot of snowmobiles. Since no one more qualified is helping I will give it a shot. Black plugs usually mean rich. The main jet and the needle take you from off idle to full bore. With new plugs in I would start with raising the needle clip one notch first. I don't know how many notches there are on your needle but if you are already in the top notch you will need to start with the main. I live at 4300' and ride up from here. My 06 400 Max came with the high altitude kit in the carb and clutch. I rode for a year with the same plugs and they looked great. I hope you find something in this post to get you started. Later! Frank

 

so the higher the altitiude the leaner the mixture or is it richer im still new to this thanks for the help.

 

The higher up you go in altitude, the thinner the air gets. This means you need smaller jets to give the engine less fuel as you go up. Engines run the best at sea level (or below).

The first thing you need to do is a compression test to get a baseline. I've seen a lot of people at the race track mess with jetting only to find out their engine is way down on compression and in need of a rebuild.

If the engine compression comes out good then the next thing to do is go down in size with the main jet. Sorry, I can't give you a baseline for jetting because I don't own a DS. Someone else on here will help you with that figure.

A lot of REALLY good racers in this forum. They know their stuff and are glad to help.

 

it has plenty of compression it has less than 20 hrs of use on the motor.