just wondering

[ex_freestyle]

o.k. as the subject title says i was wonder what will happen if you over tighten the air and fule mixture screw on the carb, the reason im wondering this is because it about minus 10 - 15 out where i live and my quad is not idling worth smurf so i decided to tighten it as much as it would go until it turned again and now it wont even start so i was wondering did i strip somthing or snaped a cable on the inside or what, sure i checked it out a bit but never pulled it apart yet

thanks

[hornetgod13]

If you have the right sized pilot jet than when you tighten it until it stops it will not run. That is normal. Now if you kept turning past that than you might have stripped or broke something.
You need to open it back up to 1 and 1/2 to 2 and 1/2 and find what best works for you. See if will start back up.
Cold weather starting is a weakness of the 400EX. Most people, me included, put a #42 pilot jet in the carb. The stock #38 jet makes cold weather starting difficult.

[hornetgod13]

Originally posted by ex_freestyle
now it wont even start so i was wondering did i strip somthing or snaped a cable on the inside or what, sure i checked it out a bit but never pulled it apart yet

It's a brass screw with o-rings and a spring. It has a tapered needle tip that controls the fuel/air mixture. The more you screw it in the thinner the mixture. The more you open it up the richer the mixture is.

Below is an Illustrated Parts Breakdown of the carb. It's item #6. It costs $17.25 to replace