300ex hmf help me out with jetting

[4wheelboy]

i jus put my hmf on my 300ex and i need to jet it. do any of yous no where to start from? what size jets? and i always hear about puting in a 42 pilot in the winter for 400s but wut about 300s?.

any help is greatly apreciated:)

ohh and do u think i should run a lid. some times its gets alil muddy where i ride. will removing the lid make that much of a diference:confused:

[hondafox440]

Go up one size on the main and pilot (from what you have now) and richen the needle one notch. See how it runs, and adjust accordingly. If it sputters and surges, richen it more, if it bogs, go back to your current jetting.

[wilkin250r]

Agreed. A pipe isn't going to make a HUGE difference in your power, so you won't need to make a huge jetting change. Start with one size bigger on the main, one size bigger pilot, and use that as a starting point.

[cals400ex]

i personally don't think removing the lid makes that much more power. it feels like it has more torque, but i think a lot of that is in your head. also, the extra noise and rumble on the bottom of the seat makes you feel like your getting more power than what you really are. if its muddy, i would leave it on.

[4wheelboy]

Originally posted by cals400ex
i personally don't think removing the lid makes that much more power. it feels like it has more torque, but i think a lot of that is in your head. also, the extra noise and rumble on the bottom of the seat makes you feel like your getting more power than what you really are. if its muddy, i would leave it on.

ok thanks:cool:

[ZSK]

When I pulled the lid off of my 300 it helped a lot. This is because my jetting was way off. It was equivilent to putting a pipe on it. I bought mine at auction and the guy put the stock pipe on it before it was repo'd. Mine jetting was just about perfect after that. I just put an FMF full system on and it's a little lean without changing the jets. I need a size bigger on my main, pilot, and need to move the clip. I'm running a K&N filter, no lid, and an FMF and it runs pretty good.

[300exOH]

I think pulling the lid off helped big time. I'm running a 135 main(122 stock) with a UNI with my Sparks and it seems to be perfect. It does get much louder with the lid off but it sounds mean.:macho

[cals400ex]

if your rich on the main in the first place, removing the lid will help out on power.
300exOH, in my opinion your too big on the main. ask sparks what they recommend for jetting. i bet with a sparks pipe, filter, and no lid, a 130 is plenty big. try putting a 130 keihin jet in and see how it runs. i have a feeling sparks is going to recommend a jet a lot smaller than what i am telling you to run. i have a feeling they will recommend a 125 or so without the lid on. give them a call.

[300exOH]

Actually, Sparks is the one who sent the 135 keihen. I haven't had much time to mess around with it. I'm thinking it should be fine for the winter but I may back off to a 130 when it gets warmer out. Thanks for the input though.

[Aceman]

I agree with cals400ex, I think your main is way to big. I live on the coast at sea level with a 330 kit and I have a 132 mj in mine.

[4wheelboy]

what would u guys recommend for me with dynojets?:confused:

and by the way its with the lid on

[cals400ex]

boy, i can't believe sparks sent you that big of a jet. on my 400ex, they said to leave the stock mainjet in after the installation of his pipe unless i was removing my airbox lid. then he said go up two sizes. sorry, i don't use dynojets. i would pay close to their directions. if their directions are off, i bet their a little rich, but thats just a guess.

[westcoastmxer]

im runnin a 132 main jet with my tc racing exhaust,uni and airbox lid off.seems very good.

[Honda5]

????? is the main jet on a 300ex the hex style or the the flat screwdriver style???? I just picked up a 130 from my dealer and it is the screwdriver style (I think it is wrong and dont want to pull carb til I have correct jet)

[Aceman]

A Keihin mj is hex shaped with a screwdriver slot at the top. A pj is round with a screwdriver slot at the top. I believe dynojets are round also.

[cals400ex]

Originally posted by Aceman
A Keihin mj is hex shaped with a screwdriver slot at the top. A pj is round with a screwdriver slot at the top. I believe dynojets are round also.

keihin makes a couple different mainjets. i think, but not positive, that the 300ex uses a hex mainjet. when you find out for sure from someone that has jetted a 300ex, then go to the dealer. by the way, if it is a hex, it will be a keihin 13 series mainjet. or just go to the dealer and make them look it up on the computer. they should be able to tell you that in no time. i still think it is a 13 series jet (hex). the hex jets don't have a slot in top for a skrewdriver either.

[Honda5]

ok ,it figures they gave me the wrong jets. thanks this will keep me from pulling it apart twice.

[Aceman]

My mistake, the keihin main jet for the 300ex is hex shaped without a screwdriver slot. I wasn't thinking clearly or something.

[Honda5]

thanks