I see people talking about either removing the airbox lid (im still unsure what this means....the top of my airbox consists of an oval piece of metal held by 2 wingnuts, under which is my k&n....is this the 'lid'?? or are we talking the black 'snorkel' type rubber boot taking the box from 2 holes down to one?)

Also, someone mentioned widening the black boot type thing at the opening?


Then I hear about HPD airbox kits,but dont see them on their website for the 400 Scrambler.

Some people mention drilling holes?

I definitely want some sort of box because i will see some water time to time...


Regardless of the route I choose, I understand jetting will be in order. Can you point me to a jetting walk-through? Ive done it 100 times on my camaro....but never a quad. Does the carb need to come off, or can i do it with the carb on? Jets are found behind the fuel bowl?

 

First thing get rid of K&N! Great for cars but allow too much dirt. Have seen too much damage because MOST times filter is not cleaned and oiled enough! UNI foam filter much better if not using stock! This is from over 20 years of service work. Just trying to make your piston last longer! Every one I've repaired because of grit and dirt owners have gone back to stock or UNI! Recently had to bore and install new piston in 2006 sportsman 500! The 500 engine is at LEAST a 10-12 year engine with proper maintenance! I'm sure to get negative comments,but Most people dont see what I experience everday. Sorry for the long post. Jetting only necessary if free flowing exhaust and better air flow is done. Rule of thumb, 10-20% for jetting up. If running say 230 main,try 250,run engine 3/4 throttle,kill at speed,check plug ,should be medium tan,not white. If lean continue up. Raising needle may help also. main jet in carb bowl,CANT miss it. Good luck!