My buddy has a 400ex and very little budget. He wants more power to keep up with the faster riders/quads in our group. He was thinking of modding his exaust and airbox and maybe re-jetting.

Any suggestions on how to get more power using stock parts and maybe go as far as a jet kit??? (very limited budget)


Thanks

 

My only suggestion is to scrap the Air-Box and get a Uni-Filter to clamp on the back of the carb. Then rejet and that will give you some more power. Good luck to your friend!

 

Just rejet(42 and 152). If on limited budget, stay with the stock airfilter, but get and outer wears cover for it. The money will be better spent on a exhaust slip on. The HMF is a good system for the money. Take the head pipe off and clean out the welds.

 

Get the HMF slip-on and put 4 1" holes in your airbox. That will be enough power and won't cost that much. You will also need to rejet. I run the HMF and it is an awesome pipe.

 

Low budget huh?
How about drilling 3 or 4 1/4" holes in the end of the baffle (the part that unbolts from the muffler) so exhaust flow will be picked up. Next, lower the needle clip one notch....effectively raising the needles and allowing more fuel from 1/8 - 3/4 throttle. Pop a couple of holes in the lid, trim off excess intake snorkle in the air box, and raise the main jet too high and work down 'till the engine pulls hardest with a nice tan plug. I done this when my previous 400ex was stock.

 

Pull the whole air filter cover off. Put a k&N jet kit on it. Theese two things alone put on more power than my $450 noleen pipe.

 

i took the spark arrestor off the back of the exhuast and i was amazed at the turqe it added. there are only three hex bolts on the back you have to pull off, 5/16 inch i think.

my 400 is stock for now but i plan on getting a hmf slip on, dyno jet kit and a air filter.

 

Well, low budget... I was going to suggest a turbo charger, with intercooler, the turbo charger comes with a turbo charger, air filter, air box, pipe, filter ect... its literally nearly tripples the hp. Stock 400ex:28hp, with tc:64hp, and thats WITHOUT nos! Add nos, its the fastest thing, ever.

 

I say take the air box lid off, k&n filter,put a 40 pilot jet then take the choke out of the carb(better air flow),re jet the main,then take the baffle out of your stock exhaust.