I have an Arctic cat 650 atv and recently did the airbox mod. The instructions that came with the kit suggested a 137 jet in the front carb and a 142 jet in the rear or second carb. Problem I am having is flooding at idle and the atv is running rich with a lot less power than stock. The only mod is the cdi unit from Highlifter which I have on a switch. I find a big loss in power. I am at or just above sea level. I removed the washer on the needles. still no better. I changed jets to 135 front and rear. This was a little better but not near as much power as stock. Anybody with any good ideas or suggestions. I am thinking about going with a little smaller jets and if that does not work, going back to stock jets and removing the airbox mod. I only tried the airbox mod for better gas mileage as we sometimes run the highlands in Cape Breton even with extra gas my range is limited. Any suggestions would be helpful.

 

Howdy neigbor.My mom was from the Island,my second home.

I have a VDI snorkle with 142.5 front and 147.5 rear main jets with one washer under each shim.Works really well for me.Are your jets kehin or dyno jets?

 

My jets are Kehin. I am going to try 2 130 jets on the weekend. To correct my post, my bike is idling fine. it seems to be loading up while on the throttle part ways open. It might even be that way at full throttle. It is running rich and I have rulled out the choke. I will more info the weekend.

 

You might try dropping the needle a notch or two.

 

If you had the carbs off, I'd check your choke cables real good. It dosen't take much to have these things not aligned correct. What you described sounds like your chokes are hanging up. Half throttle problems would be your needles, and if your running with no shims, there's not much more you can do. Adding a shim lifts the needle out of the bore a little bit, allowing more gas in. I'm almost positive you have a choke problem. As for your jetting, main jets effect 1/2 to full throttle. The numbers you stated sound about right if they're Dyno Jet jets. If your using Kehin jets, you should be around 142/147 respectively. Dyno Jet numbers run lower in comparison to Kehin numbers.