spputering.

[justin1022]

hey guys i am 15 years old and just rebuilt my 400ex. its now a 440 and has hot cams stage 2 and a exaust coming its just a little bit late. but i put the engine in last night and bolted it all pu the morning and it fired up liek a charm i was so proud. it runs prefect idling. then i was doing a walk around when it was idling and i noticed my side gasket were the clutch is was leaking pretty bad but i guess it must of dryed out when i pulled it apart to put the hd timing chain on. but that wasnt goingo to stop me from trying it out! first year was perfect and once i hit 3rd i wanted to see what it got so i punched it and holly man its torquey. but anyway after 3rd i got the worst sputter in 5th you cant get past 1/4 throttle. i dont no what it coudl all be im leaning towrds eather to big of a jet or a dirty pilot jet. can someome help me out hear. ? and i just thought MAYBE i could be running to much octane i am not sure of this though it might sound really dumb i havent delt with race gas before i am running 113 octane. and most guys i no with 12.5:1 compression run just premium.

thanks in advance for the answers.

[Honda#4]

Needle and the main might be lean.

[drew416ex]

I dont know of any one that is running premium with 12.5:1 unless its a factory engine. In that case the timing is set so it can run a lower octane. As far as your problem, what main are you running?

[justin1022]

Originally posted by drew416ex
I dont know of any one that is running premium with 12.5:1 unless its a factory engine. In that case the timing is set so it can run a lower octane. As far as your problem, what main are you running?

yea i only no people with the new 450rs. they are the guys that told me to stop wasteing my money on race gas because premium is good enough. and my main is a 170 dyno jet and my needle is in the middle clip. i was thinking of dropping to a 168 or so..

[drew416ex]

Yeah tell them to shut their hole cause you cant run it in a 400ex with 12.5:1. The factory has built those to beable to run 93 for the consumer. As far as your main, im not sure what a dynojet equals in a keihin so its hard to tell you what you should try. it will also do what you describe when its running too rich.

[justin1022]

Originally posted by drew416ex
Yeah tell them to shut their hole cause you cant run it in a 400ex with 12.5:1. The factory has built those to beable to run 93 for the consumer. As far as your main, im not sure what a dynojet equals in a keihin so its hard to tell you what you should try. it will also do what you describe when its running too rich.

rich is tom much, right? i will put like a 168 or a 165 in in a couple mintues and see what she does i want to test it on the track so bad!!!!

[drew416ex]

yeah rich is too much.

[justin1022]

Originally posted by drew416ex
yeah rich is too much.

k Drew this is messed i dropped in a 165 main and it still sputters just as bad and a factory is a 158 so its not even a big jump i am wodnering about a plugged pilot jet?

[drew416ex]

Factory is a 148. Your pilot jet isnt used after 1/8 throttle. If it were clogged, it wouldnt idle. Is the boot going from the airbox to the carb all the way on? Ive had it come partially off and sputter at half throttle.

[justin1022]

Originally posted by drew416ex
Factory is a 148. Your pilot jet isnt used after 1/8 throttle. If it were clogged, it wouldnt idle. Is the boot going from the airbox to the carb all the way on? Ive had it come partially off and sputter at half throttle.

um oops? i was looking at that and it didnt look all the way on. but i didnt think it would make any diffrence. and my main jet for sure is not plugged because its a brand new one. gas is clean as a wistle. so it might be that i will try it out tomrow morning. but other then that what could it be? any suggjestions if that doesnot work. o yea and when im on idle it dont bog at all you can rev it right up it wont bog at all and then it sometimes is good in 1st and the rest of the gears have a bog in them.

[justin1022]

ok Drew, i fixed that air boot and it rides good on top eng now but i meen you have to be past 3/4 or else it bogs and on bottom end meh some parts its alright but most has a bog in it. so i was thinking. its getting to much fuel still and i thought that because when its on top end and it calls for lots of fuel it get it but on the middle it doesnt want as much but its getting to much. correct me if im wrong. but its weird. it is almost like its getting not enough because i just went down the drive way and back with it and was riding on top end and when i got to the shop and shut it off the header was just ticcking.

[drew416ex]

Ok, what is the mixture screw set at, what pilot jet is in it, where is the clip on the needle, and what main jet is in it?

[Honda#4]

You should be running something around a K170 main, a 170 dynojet is equal to a K190 so I think your way to rich on the main.

[drew416ex]

Originally posted by Honda#4
You should be running something around a K170 main, a 170 dynojet is equal to a K190 so I think your way to rich on the main.

Ive been wondering, how do you figure out what the dynojet equals to a keihin? I cant find it anywhere.

[Honda#4]

Here ya go man,


Width------Keihin # -- DynoJets # -- Mikuni #
0.0350---- 92.5--------- 92----------- 86.3
0.0360---- 95----------- 94----------- 88.1
0.0370---- 97.5--------- 96----------- 90.0
0.0380---- 100---------- 98----------- 91.9
0.0390---- 102.5------- 100---------- 93.8
0.0400---- 105--------- 102---------- 95.6
0.0410---- 107.5------- 104---------- 97.5
0.0420---- 110--------- 106---------- 99.4
0.0430---- 112.5------- 108--------- 101.3
0.0440---- 115--------- 110--------- 103.1
0.0450---- 117.5------- 112--------- 105.0
0.0460---- 120--------- 114--------- 106.9
0.0470---- 122.5------- 116--------- 108.8
0.0480---- 125--------- 118--------- 110.6
0.0490---- 127.5------- 120--------- 112.5
0.0500---- 130--------- 122--------- 114.4
0.0510---- 132.5------- 124--------- 116.3
0.0520---- 135--------- 126--------- 118.1
0.0530---- 137.5------- 128--------- 120.0
0.0540---- 140--------- 130--------- 121.9
0.0550---- 142.5------- 132--------- 123.8
0.0560---- 145--------- 134--------- 125.6
0.0570---- 147.5------- 136--------- 127.5
0.0580---- 150--------- 138--------- 129.4
0.0590---- 152.5------- 140--------- 131.3
0.0600---- 155--------- 142--------- 133.1
0.0610---- 157.5------- 144--------- 135.0
0.0620---- 160--------- 146--------- 136.9
0.0630---- 162.5------- 148--------- 138.8
0.0640---- 165--------- 150--------- 140.6
0.0650---- 167.5------- 152--------- 142.5
0.0660---- 170--------- 154--------- 144.4
0.0670---- 172.5------- 156--------- 146.3
0.0680---- 175--------- 158--------- 148.1
0.0690---- 177.5------- 160--------- 150.0
0.0700---- 180--------- 162--------- 151.9
0.0710---- 182.5------- 164--------- 153.8
0.0720---- 185--------- 166--------- 155.6
0.0730---- 187.5------- 168--------- 157.5
0.0740---- 190--------- 170--------- 159.4
0.0750---- 192.5------- 172--------- 161.3
0.0760---- 195--------- 174--------- 163.1
0.0770---- 197.5------- 176--------- 165.0
0.0780---- 200--------- 178--------- 166.9
0.0790---- 202.5------- 180--------- 168.8
0.0800---- 205--------- 182--------- 170.6
0.0810---- 207.5------- 184--------- 172.5
0.0820---- 210--------- 186--------- 174.4
0.0830---- 212.5------- 188--------- 176.3
0.0840---- 215--------- 190--------- 178.1
0.0850---- 217.5------- 192--------- 180.0
0.0860---- 220--------- 194--------- 181.9
0.0870---- 222.5------- 196--------- 183.7
0.0880---- 225--------- 198--------- 185.6
0.0890---- 227.5------- 200--------- 187.5

[Honda#4]

For awhile I had a rough time jetting with dynojet on my quad so I switched to the back to running keihin jets and it feels better, when my quad was stock it ran better with dynojets.

[justin1022]

ok thanks man so i should be running a dyno jet 154 you say? the closest i got to that is a dyno jet 155 thanks a bunch i wil rty it out in a bit. and post what happens. thanks!

[justin1022]

Originally posted by drew416ex
Ok, what is the mixture screw set at, what pilot jet is in it, where is the clip on the needle, and what main jet is in it?

Drew, my main is a 165 right now but i have learned i need to put a 155 in it. i will try it redaway. and my mixture screw i am not sure i tryed turning it but itt wouldnt move and i didnt want to trip it so i just left it. and my needle is in the middle clip. and my pilot jet is a stock one. honestly i think my problem is the 165 thats in it. so i will put the 155 and post what happens. thanks.

[Xsapper]

you realize that you're going to have to go though all this again once your new exhaust comes in, right?

anyway ...for what you're trying to work with right now:

like someone said, if it idles your pilot jet isn't plugged ..also, pilot jet pretty much affects only up to 1/4 throttle or so

if it pulls hard and smooth at WOT, your main jet is fine

if it won't cruise (1/4 to 3/4 throttle) your problem is likely the needle clip setting.

it's hard to say whether your midrange is lean or rich without seeing and hearing the bike but it doesn't really matter ...all you have to do is move the clip in one direction , if that doesn't work then go the other way

my guess though is that you're lean and need to drop the clip

[Honda#4]

Yea a dj154 should be a good spot to start.

[justin1022]

ok, i just dropped the 155 in and its perfect doesnt backfire or anything. man does the 440 got some jam!4th gear sitting down it just pulls right up! i cant weight to go on the trac kthat will be in a couple minutes. thanks a bunch guys. what woudl you guys recomend with a pipe on?

[mooseracerX]

When you punch the gas it just stalls and almost quits? Mine did that last weekend. We cleaned the carb and put a new spark plug in and it ran good the rest of the day and still runs good.

[justin1022]

Originally posted by mooseracerX
When you punch the gas it just stalls and almost quits? Mine did that last weekend. We cleaned the carb and put a new spark plug in and it ran good the rest of the day and still runs good.

thnaks i thought it was that to. but i fouund out i was jetting way way to high i was running a 170 at first then dropped to a 165 the na 155 and it runs like a top now!

[mooseracerX]

Yeah in that post right above mine I saw you got her running I we just posted at nearly the same time. ha

[Honda#4]

You may have to go up one on the main when you get a pipe.

[justin1022]

Originally posted by Honda#4
You may have to go up one on the main when you get a pipe.

Honda#4, i think i might be alright. i noticed wile i was flying to the track i let off to cross the texas gates and it backfired out of my exaust. from what i no i am pretty sure that means its still getting a bit to much fuel because its going into the pipe and combusting there and creating a backfire. correct me if im wrong.

[Honda#4]

If its backfiring during decel its still running lean, if its backfiring with blue smoke then yes your running rich yet. Like you said if you are still rich you should be good if you put a pipe on, you may to tweak the A/F screw a bit but very minor.

[drew416ex]

you need a 42 pilot jet. It backfires when you let off becuase its lean on the pilot circuit.

[justin1022]

Originally posted by drew416ex
you need a 42 pilot jet. It backfires when you let off becuase its lean on the pilot circuit.


so you say i should put in a 42 pilot? it idals fine though. but i will figure it out tomrrow because my pipe wil be in tomrow so i will pick that up. then drop it on my quad. and see if it still backfires. if so then i guess i will drop a 42 pilot in. thanks.

[justin1022]

Originally posted by drew416ex
you need a 42 pilot jet. It backfires when you let off becuase its lean on the pilot circuit.

Drew, i was just racing a yfz and i was infront of him!!! and i turned the corner and smoked this little bump thing in like 3rd then grabbed 4th and smoked my big gap and right of the lip it sputtered. then it started nosediving so i leved it out but somehow i over jumped it and bam my woopes just a couple feet infront of me. usally i just smoke them in 4th and clear the hole set. so i just punched it but it sputtered just like before and i came short and baled because my quad was about to go end over end! ha so i am wondering what this sputter is comine from now. i am going to check that air boot. and other then that what would you say?

and for my quad? nothing really it was flying in the air virtically then the bumper hit the ground and it did a complete front flip and landed on he front wheeles and then the back wheeles set down. lucky nothing happend.

[drew416ex]

Originally posted by justin1022
so you say i should put in a 42 pilot? it idals fine though. but i will figure it out tomrrow because my pipe wil be in tomrow so i will pick that up. then drop it on my quad. and see if it still backfires. if so then i guess i will drop a 42 pilot in. thanks.

Yeah it will idle fine and seem like it runs fin to 1/4 throttle, but the stock pilot is not giving it enough past idle. Try it out, it should fix it.

[drew416ex]

Originally posted by justin1022
Drew, i was just racing a yfz and i was infront of him!!! and i turned the corner and smoked this little bump thing in like 3rd then grabbed 4th and smoked my big gap and right of the lip it sputtered. then it started nosediving so i leved it out but somehow i over jumped it and bam my woopes just a couple feet infront of me. usally i just smoke them in 4th and clear the hole set. so i just punched it but it sputtered just like before and i came short and baled because my quad was about to go end over end! ha so i am wondering what this sputter is comine from now. i am going to check that air boot. and other then that what would you say?

and for my quad? nothing really it was flying in the air virtically then the bumper hit the ground and it did a complete front flip and landed on he front wheeles and then the back wheeles set down. lucky nothing happend.

That has happened to me a few times and every time it was the air boot. If it was running fine and then suddenly went to crap, that would be my guess.

[justin1022]

Originally posted by drew416ex
That has happened to me a few times and every time it was the air boot. If it was running fine and then suddenly went to crap, that would be my guess.

yea it was that. the problem was it was to far in the other boot but i pulled it all apart and now its good. thanks.