View Full Version : Spark Plug & Jetting
juice420
05-21-2010, 01:47 AM
So I bought a lexx slip-on and powerlid a while ago and took my quad to the dealer to have it jetted. I know they put a 140 mj in but I'm not sure about the pj or the needle. I recently put a K&N pro flow intake on and rejetted to a 155 main and it ran good the first day. Now it's kinda poppin again in the low end, mid and top are fine. I took out the plug and it's got black dry carbon on it. Doesn't that mean it's running rich though. It doesn't really make too much sense to me I thought a 155 would be a little small. Anyone got any ideas??
juice420
05-21-2010, 02:39 PM
common guys feel free to jump in at any time lol.
twincat800
05-21-2010, 02:41 PM
You probably need a 25 pilot jet. Im guessing a 155 main jet would be okay.
twincat800
05-21-2010, 02:44 PM
Where are you in michigan? Im doubting it but theres a slight chance i could find my old jets.. im 15 min west of det
cataway
05-21-2010, 02:44 PM
Originally posted by juice420
So I bought a lexx slip-on and powerlid a while ago and took my quad to the dealer to have it jetted. I know they put a 140 mj in but I'm not sure about the pj or the needle. I recently put a K&N pro flow intake on and rejetted to a 155 main and it ran good the first day. Now it's kinda poppin again in the low end, mid and top are fine. I took out the plug and it's got black dry carbon on it. Doesn't that mean it's running rich though. It doesn't really make too much sense to me I thought a 155 would be a little small. Anyone got any ideas??
i would rather you try a 142.5 MJ it may be time for a 25PJ if turning the fuel screw out as much a 3.5 turns does not get it right
defintely go with a 25 pilot jet...and try bringing your main back down to 150 at least....black always means a rich fuel condition....make sure you change your plug also....buy at least 3-4 plugs you will need them for proper plug chops and checks
juice420
05-22-2010, 01:18 AM
how would I be able to tell what size pj is in it right now? Would it be marked like the mj's are? Do you guys think when I had the dealer jet it that they would put a 25 pj in?? Doesn't the Dynojet kit come with a 25 pj? When they jetted it I think all I had was my slip on and maybe the powerlid. Oh, and Twincat I'm in Lincoln Park.
typo on my reply my bad...definitely go with a 25 PJ...the stock PJ is 22.5 and I haven't seen a dnyojet kit come with a PJ......and i'd still recommend a 150 MJ with a silencer and an open airbox for sure.....I just pulled the PJ out of my DVX today and it was 22.5
Originally posted by juice420
how would I be able to tell what size pj is in it right now? Would it be marked like the mj's are? Do you guys think when I had the dealer jet it that they would put a 25 pj in?? Doesn't the Dynojet kit come with a 25 pj? When they jetted it I think all I had was my slip on and maybe the powerlid. Oh, and Twincat I'm in Lincoln Park.
I doubt they changed the pilot but its possible, just ask them....only way to check the pilot is to pull the carb off and pop off the bottom..and im with cataway..i think the 155 is a bit large for a slip on system...142.5 or a 150 maybe
juice420
05-27-2010, 02:00 AM
Originally posted by sd1
I doubt they changed the pilot but its possible, just ask them....only way to check the pilot is to pull the carb off and pop off the bottom..and im with cataway..i think the 155 is a bit large for a slip on system...142.5 or a 150 maybe
I also have the pro flow k&n intake and powerlid, not just a slip on. do you still think i should bring the mj down to a 150?
Originally posted by juice420
I also have the pro flow k&n intake and powerlid, not just a slip on. do you still think i should bring the mj down to a 150?
well if it were me i'd go with a 25 pj and a 150 mj and do some plug checks...i'll bet you will be very close to where u need to be...but thats a good starting point for sure...remember that the stock head pipe is very restrictive above say 3/4 throttle or 7500 rpm....but it gives you decent low and mid range..... its not really to hard to do this yourself and you can save yourself a lot of money....then you can use that money to buy yourself a dyno jet kit ..... feel free to ask me any questions on jetting or carb removal...thru pm or here...
juice420
05-27-2010, 01:10 PM
Yeh, I know how to jet and I already have a dynojet kit, I'm just trying to find the sweet spot.:cool:
Originally posted by juice420
Yeh, I know how to jet and I already have a dynojet kit, I'm just trying to find the sweet spot.:cool:
sorry man my bad......:)
juice420
05-28-2010, 02:52 AM
Originally posted by sd1
sorry man my bad......:)
Naw, don't have to be sorry dude. Your just trying to help. That's what we do at ATV Riders!! But anyway...I put a 25 pj in and a 150 mj a plug check and still seems to be running a little rich. I haven't messed with the needle yet though. I dunno maybe I'll go to a 146 mj. Oh yeh and the fuel screw is 3 turns out. I just can't get rid of that pesky low end stumble. I hope I get her right before Memorial Day!!!
well where is it stumbling throttle wise? about 0 to 1/4 turn? or is it 1/4 turn or more?
juice420
05-28-2010, 12:33 PM
It's weird...it does it when I stab the throttle, if I ease into it it's fine. Other than that it runs good.
hmm..sounds more like a fuel pickup issue than a main jet........so when u stab it it sputters on the low end only?....might want to check your float level along when you change your pj
juice420
05-29-2010, 01:56 AM
Right. But that still wouldn't explain why the plug is showing signs of running rich. I thought a 150 mj would be spot on. Plus, I'm pretty much at sea level so that's not a factor. But anyway I'm leaving to go up-north as we speak so I'm gonna ride it how it sits right now. Hopefully it's not too rich.:ermm:
hope you were able to change the pilot before you went riding...have a good time man.....take some pics he eh
juice420
05-31-2010, 09:19 AM
well i put a 25 pilot in and turned the fuel screw out 3 1/2 turns and it still stumbles when i stab it in low rpm's. Kinda pissin me off because now I can't do wheelies.:scary:
But I had a blast up north still.
cataway
05-31-2010, 12:16 PM
back when i was using the bsr carb there was a need to go to a 27 pj . any time the screw is out 3 1/2 turns then a step up to the next jet is hinted at.
my finnell jetting was 172 mj 27 pj i dont remember how many turns out on the screw
89'350RX
06-19-2010, 02:35 PM
My Son just bought a 06 KFX400 and we just installed a LEXX pipe (extremely nice) and aftermarket air filter (twin air) and used the MOOSE RACING jet kit specific for the wheeler and I just wanted to say the jet kit is DEAD on. Installed per instructions and it runs perfect. :) :)
Biggest pain is removing the carb bowl (screws are a bitcchh to remove) and the carb is tucked in there pretty good.). My 400ex's are so much easier to jet but overall, nice quad.
4wheels1004
08-15-2010, 10:47 AM
ok so i read through all the post and you guys seem to know what your talking about.... so hears the problem im out of minnestota and i rebuilt my 03 z400 this last winter i the stuff listed below on it. but anyways i jetted it this fall when it was about 65 degrees out or so with a 170 i think? it ran great!!! i had not rode for a while and then went out for a ride and as soon as the engine heated up it started bogging out so i thought maybe there was something in the carb. so i took the carb apart and cleaned it it ran better but as soon as it heated up again it started sputtering and not wanting to run. any suggestions would be extrememly helpful thanks guy.
juice420
08-21-2010, 06:59 PM
Originally posted by 4wheels1004
ok so i read through all the post and you guys seem to know what your talking about.... so hears the problem im out of minnestota and i rebuilt my 03 z400 this last winter i the stuff listed below on it. but anyways i jetted it this fall when it was about 65 degrees out or so with a 170 i think? it ran great!!! i had not rode for a while and then went out for a ride and as soon as the engine heated up it started bogging out so i thought maybe there was something in the carb. so i took the carb apart and cleaned it it ran better but as soon as it heated up again it started sputtering and not wanting to run. any suggestions would be extrememly helpful thanks guy.
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cataway
08-21-2010, 07:51 PM
Originally posted by 4wheels1004
ok so i read through all the post and you guys seem to know what your talking about.... so hears the problem im out of minnestota and i rebuilt my 03 z400 this last winter i the stuff listed below on it. but anyways i jetted it this fall when it was about 65 degrees out or so with a 170 i think? it ran great!!! i had not rode for a while and then went out for a ride and as soon as the engine heated up it started bogging out so i thought maybe there was something in the carb. so i took the carb apart and cleaned it it ran better but as soon as it heated up again it started sputtering and not wanting to run. any suggestions would be extrememly helpful thanks guy. what carb what jetting ?
4wheels1004
08-31-2010, 11:01 AM
not exactly positive off hand but im almost positive it has a 172.5 ? in it
cataway
08-31-2010, 05:30 PM
well if your running a 440, and your tiring to suck enough air through a 36 mm carb .............ya that could be a problem ,especially on top end.
best thing to do is get on ebay and find your self a YFZ fcr39mm carb. your going to need a cable and maybe a thumber to ,
you'll have a pleasant surprise of power to , is all very easy
4wheels1004
09-01-2010, 10:44 AM
i cheched the other night i actually have 170 mj. yeah but it seams like its doing fine on the top end, but it is cutting out/ bogging out on the lower end... but the yfz crab might be a good idea im just sick of putting money it to my Z
cataway
09-01-2010, 03:51 PM
a stock PJ is a 22.5 it is normal to go to a 25PJ after some mods.
back when i was using the bsr carb my jetting was 172 MJ 27PJ
i dont remember what turns out the screw was ,sorry
do you know what PJ your using and how many turns out the screw is ?
on th BSR carb if the screw is out more than 3 1/2 turns to get it to run then you need to go to the next bigger PJ
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