hmf jetting help

[tjd400]

I'm getting a hmf silencer and need some help from you jetting guru's(sp). Everything on my quad is stock except for a uni air filter. I've searched and found some info but would like some more info on where to start. If you have this silencer post your specs.

This is what I'm going to try to start with.

155 main
3 turns out on fuel screw
needle in stock groove
uni air filter
6 1 inch holes in lid

This is for a 400ex at about 400ft elevation.

Thanks to all that help.:D

[cals400ex]

Originally posted by tjd400
I'm getting a hmf silencer and need some help from you jetting guru's(sp). Everything on my quad is stock except for a uni air filter. I've searched and found some info but would like some more info on where to start. If you have this silencer post your specs.

This is what I'm going to try to start with.

155 main
3 turns out on fuel screw
needle in stock groove
uni air filter
6 1 inch holes in lid

This is for a 400ex at about 400ft elevation.

Thanks to all that help.:D

that sounds pretty close. you might want to put in a 40 or 42 pilot jet for easier starting in the colder months.

[fmf400ex]

i also had to mess with my needle, i had to move to the third notch from the bottom, but i have the full system.

[cals400ex]

Originally posted by fmf400ex
i also had to mess with my needle, i had to move to the third notch from the bottom, but i have the full system.

i assume you have a dynojet needle? the stock needle only has 5 different positions. so, 3 is in the middle from the factory.

[fmf400ex]

no i have stock, i forgot that the guy that had my 400ex before me had it on like the 4th notch and i moved it down. sorry about that:o

i gota hmf slip on with a 165 main stock needle on 4th position. and 3.5 turns out on air fuel.

[EvilJester400EX]

I'm running a HMF slip on, no lid, UNI filter, 175 main, 42 pilot, needle in stock position, air screw turned out 3.5 turns.

[northeast400]

my set up works great. look below

[MNTNMAN]

I m running a 155 main and 3 1/2 turns out on the screw. That is for 2000 feet. At the coast I have to go to a 160 main.

u should go to a lower mj at sealevel not a bigger one.cuz the air is denser.

[cals400ex]

Originally posted by 93 300ex
u should go to a lower mj at sealevel not a bigger one.cuz the air is denser.

the lower the elevation, the bigger the jet you use. also, the colder the air, the more dense. the high altitude jet for the 400ex is a 146 main from factory, i believe. i can just about guarantee that your bike will be faster with a 155 keihin in than a 165 keihin mainjet. i 165 is too big in my opinion. the bike will run richer with the 165 so it will probally run cooler but you won't have the same power. 165 was a couple sizes too big on my 400ex when i had x-6, uni filter, and no lid. i 158 to 160 produced way more power and actually i had a nice light tan plug color after doing a plug chop. i do jet the pilot a little rich so it doesn't run lean at low throttle positions and it also helps in starting the bike in colder weather.