jetting problem

[redexrider4290]

i just got my HMF full system for my 250ex they said they would send me the jeting so in the package i found 1 jet it was a 125 and i fiqured it was the main jet well this weekend i go to my friends and put on my pipe then i take the carb off so i can rejet it , i take it off the engine/ airbox then take the bottom bowl off i wasnt qiute sure were to put the jet then i thought it was the jet in the center of the floats and right next to the over-flow line so i took it out it had a little gold tube attached wiht holes in it then i took the top part off and noticed it said 95 so i fuigured it was the jet but then i looked at it and the jet they sent me was ALOT BIGER than the stock one well i put it in and when i try to put the bowl back on the bottom of the carb and it doesnt seal because the jet they sent me was so much longer it hit the bowl before it could close the whole way so i called a local cycle shop and he told me that the jet they sent me was probobly the wrong one and that to him a 125 seems like its to big and i should go to like a 100 0r 110 well i put the stock jet back in and re-instaled the carb so i was wandering if anyone else has had this problem i got the pipe and stuff from worldwideperformace1.com i guess i should call them and tell me they sent me the wrong jet but if someone could tell me wat the jets look like after i get the carb apart to make sure i was puttong them in the right spot that would help and wat size jets do you guys run on a 250ex with a HMF full system

WAT SHOULD I DO

[Johnny_G]

is the jet that they sent you a Hex, or a round? Meaning does it come out with a 6mm socket, or a flat screw driver?

Also your dealer is wrong.....a 100 would not be enough of an increase...somewhere between 118-130 should do it depending on elevation, temperature, and airbox mods

[redexrider4290]

the stock one was a flat screw driver but the one they sent me was i had ot use a wrench i'm not sure wat size i just used a adjustable, and i live in very southern Pennsylvania and i dont have any airbox mods (stock filter and stock lid and everything) the pipes the only mod

[Johnny_G]

If you are leaving the airbox stock, then I would recommend a 118 Keihin round part# would be 99-101-393-118.....If I were you I would buy a 115, and a 120 too just to be safe...they are under $5 each

[redexrider4290]

wat?
If you are leaving the airbox stock, then I would recommend a 118 Keihin round part# would be 99-101-393-118.....

wat part number and wat is the 99-101-393-118:confused:

[redexrider4290]

should i tell them i need a jet that uses a screw driver instead of a wrench or does it matter

[bwamos]

No,
From the sound of it your jet is a DynoJet Jeting Kit Jet. (It's actually a Mikuni Jet w/ a Keihin adapter).

Just remove the Slotted Round Jet.. then use the 6mm socket to remove the adapter. Then you can insert the Long Hex Main Jet.

Unless the 250ex is different form the rest of the Honda ATV's, wouldn't make sense if it were.

See rough detail below.

[Johnny_G]

Originally posted by redexrider4290
wat?
If you are leaving the airbox stock, then I would recommend a 118 Keihin round part# would be 99-101-393-118.....

wat part number and wat is the 99-101-393-118:confused:

(99-101-393-118) is the part # you need. that is the 118 Keihin round Main jet. The hex type would be a (99-101-357-118)

You do not have a dynojet most likely, but just to make certain....is there a "K" that looks like a star before the 125 on the jet that they sent you?

[redexrider4290]

yeah there is a K type thing i dont know if i would call it a star but it does resemble one

i called the place i got it from and they gave me the HMF Phone number and the guy i called said that i need a round jet and that Honda did something when they were making the 250's and changed something or something he said he never herd of it happening on a 03 but he said he would send me the other jet and it would be here in a couple of days

i hope i was putting the jet in the right spot on the carb i put it in the only place it would fit but i didn;t exaclty know wat i was doing and neither did my freind that was helping me

[redexrider4290]

so there is no difference between the hex jet and the round ones :confused:
i hope the round ones are a little shorter because it was the length of the hex jet that made it not fit unless i installed it rong

is this the only jet i need to replace (the main)

[redexrider4290]

is there any thing else i need to mes with to rejet liek any other jets or airscrews or anything and if i do how would i do it

[WheelerBob]

hey I'm new to the site , but i thought i would share me ordeal with HMF. I had the same problem , I have a 250ex with the same set up you have. Hmf told me that they did all of there testing on an (01)250ex and that honda must had changed the jets from the hex to the small round in the later years. They sent me the 125 small round free of charge. Nice people to deal with. Anyway to make the 125 work you have to enlarge the end of your snorkle to full size and set your mixture screw to 3 turns out. It made a huge difference on mine. Anyway hope this helps.

[WheelerBob]

O'yeah by the way just wanted to say that johnny g was right on the mark.

[redexrider4290]

which 125 did you have to enlarge the snorkle to have fit?

did the round one fit wihtout enlarging the snorkle i dont know how to do that i dont even know wat a snorkle is and do you have to adjust the air screw w/ the 125 round jet

[redexrider4290]

anyone ?

[WheelerBob]

The snorkle is the plastic tube that connect's to the front of the airbox and end's under the gastank. The original opening is about 7/8 inch, you have to cut the end off to make it full size. Mine was waaaaay too rich with the 125 main jet and the stock air box. I didn't want to take the lid off because i ride in deep mud alot. After i cut the snorkle it ran sweet, i did a plug check at wot and found a golden brown plug. And by the way i'm speaking of the keihin 125 small round jet, that's what HMF should have sent you. You need to set the mixture screw at 3 turn's out to lesson the decel popping. Mine run's sweet with this set up. Hope this help's you, let me know if it work's out for you. By the way i'm running a uni air filter.

[redexrider4290]

im runing a stock air filter instead of cutting the snorkle do you think that taking the lid off would do the same thing cuz i dont really ride in water or mud that much and when i do its usually not that deep but this time of year it is pretty dusty and is the air screw the little grey screw that is on the outside of the carb on the bottom and to the side thanks alot

o yeah and do i need to use a brand new spark plug to test it

if so will i have to buy a new one every time i do a test

[WheelerBob]

Running with the airbox lid off will work fine, but i would get an outerwears pre filter or airbox lid. The mixture screw is the small brass screw on the bottom of the carb towards the cylinder,it is pointing straight down. And yes you should use a new spark plug for a plug check, you can use your old one if you take it out and clean it real good first but it's better to use new. Also i don't know if the stock filter will flow the same as a uni, if it turn's out a little rich you may need to get a high flow filter. Hope this help's.

[redexrider4290]

you said the air screw is brass and towards the cylander and is pointing straight down right and i have to turn it 3 turns to the left for the right mixture do i turn it 3 turns out from the position it is at now(stock) and wat if my quad does run a little rich? wat will it do to the engine and stuff, will it ruin it like when it runs lean. will it rob me of power ? wat will it do

[WheelerBob]

The screw is set 3 turn's from bottom. When you screw it in make sure not to bottom it too hard, just snug it or you risk damaging the seat. Running rich will not hurt your motor, may cost a little power though. Rich is better than lean anyday, lean may cause the piston to overheat and possibly sieze, better to be a little rich than a little lean. Hope this help's.

[redexrider4290]

wat? i thought you said to screw it OUT and that would be to the left now you are saying screw it in wich would be screwing it to the right
I aint tryin to be rude or anythang but i dont want to screw this up and i dont know much about wat im doin


"The screw is set 3 turn's from bottom. When you screw it in make sure not to bottom it too hard, just snug it or you risk damaging the seat."

so i should just screw it in (to the right) the whole way

[WheelerBob]

Yes screw the mixture screw in until it bottoms out "ALL THE WAY IN" Remember not to bottom it too hard. Then back it out three full turns. I don't know how else to explain it - if you're not comfortable doing it yourself rather than mess it up take it to your local shop. They shouldn't charge anymore than a hours labor to jet it and set it up.:D

[brokeitin3]

that sucker is going to be running way too rich. a 125 main? a 96 is stock and the only mods are the exhaust. a 105 would be plenty. i got the a bigger piston, cam, and exhaust and a 105 main is all i had to go up to.

[WheelerBob]

Did you use a dyno jet 105 or a keihin 105? Remember dyno jet and keihin numbers do not match. A keihin 125 is roughly equivalent to a 115 dyno jet. Mine runs good with the 125 with the snorkle cut off and the uni filter but I set my up in 45-50 degrees come summer time it may run a little rich. Otherwords I may have to go down to a 120 but for now it runs good.:eek2:

[redexrider4290]

so if i put the 125 in,screw the mixture screw in then 3 turns out ,and take off my air box lid i should be fine?

i'll try and clean my plug and then run it hard and check it because i dont have any new ones

[WheelerBob]

Yes you should be fine, but just to let you know I rejetted mine yesterday down to a 118 keihin, I hadn't really ridden mine since the weather warmed, it ran great with the 125 in the cold weather but when I took it out yesterday it seemed to be running rich and was sluggish. Brought it home and put in a 118 and bam right back to the way it was. Look's like i'll have to run the 118 in the summer and the 125 in the winter. Just thought i'd let you know. I bought this quad in october and didn't pipe and jet it until feburary, this is the first time i've ridden it in above 50 deg weather. So for right know the 118 is right on, but yesterday it was about 75-80 I may have to rejet again in the heat of the summer when it get's to 90-95 deg on a regular basis. We have a big temp swing here in Baltimore it range's from 10-20 deg in the winter to 80-100 in the summer so if i stick to the rule and rejet every 20 deg temp change i'll be changing jet's alot. just wanted to keep you in the loop so to speak. Hope this help's.:D

[redexrider4290]

yeah i probobly wont do that because this is the only jet i have and i dont ride that much and i think the like being off should lean it out a good bit and i get pretty much the same weather as baltimore i only live like 30-40 miles away from there i live right on the PA-Maryland line. wat part of baltimore do you live in

[redexrider4290]

will i still feel a power difference if it is runing a little lean, maybe ill take the lid off and if its still runing lean ill cut the snorkle to:ermm: that should lean it out a bit ,but ill probobly have ot clean my filter alot

[redexrider4290]

about how big is the air-screw and what tool do i need to turn it

and my pipe now hos it is (not rejeted yet) pops all the time it is really anooying and sounds like crap if i hit the gas or shift it doesn;t but as soon as i let off the gas a little bit POW POW PING POW BA BA BA POW

will this stop once i rejet and screw the air screw