400ex will run w/o main jet!!

[kajunracing]

I went to change my main jet because I was way to rich and when I took off the cap on the carb bowl my jet was laying inside of it!!! Im running a 170 (dyno) main and was going to down a size and realized that it will run w/o a jet in. I still dont know if it is tight enough to stay in. guess Ill see

[Martin Blair]

yeah it will run the main jet only does wot so you wont even notice it util you run WOT for a few seconds to get it to open up.

[skemp]

That's weird that you didn't notice anything. Whenever my main has fallen out, it WILL NOT run past a quarter throttle. The motor is sucking so much gas at that point that it just sputters and dies out. Hey, maybe you don't have to jet down afterall, maybe you just need to run a main jet in the first place to get rid of that pesky full throttle stumble... :D

[wilkin250r]

Hmm, conventional wisdom says your quad should have coughed and sputtered an anything above 1/4 throttle.

Check and clean your carb, you may have junk in there restricting the fuel flow to keep it from running rich.