Carb tuning: the be all and end all thread?
06-07-2009, 01:15 PM
#1
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Carb tuning: the be all and end all thread?
Okay, i know this topic has been beaten to death but every topic has one part covered but another ommited....so searching for pertinent data can sometimes be hard.
If some of you guys remember i had a shop install a DynoJet stage I kit about a month ago....about a week later it started to stutter and stumble at low RPM (read below 3000) when warmed up...it was doing this before and i was hoping that the DJ kit would cure that...well, nothing.
Symptoms were:
1/8 to 1/4 throttle below 3.000 rpm the bike would stutter, jerk, buck. full throttle would clear it, as soon as it climbed past 3000 rpm, the symptoms would go away.
Random stalling at lights, sometimes when leaving a light it would just stall and die...leaving me no choice but to slip the clutch when leaving the light. otherwise i'd look like a SQUID with no clutch control
Throttle had an on/off feeling, very hard to moderate throttle at low engine RPM leaving me no choice but to be in a low gear/higher rpm during corners so the throttle would unsettle the bike.
So today i decided, after much reading, that shimming my needle might possibly cure my problem, OOR, adjusting the fuel mixture screw.
anyways, i pulled the carbs out, took apart the diaphragm and realized that DJ needles have grooves on it for adjustment, so happily i came here and people talk about 5th grove, 4th grove...bla bla bla, but nobody says measuring from which size? from the top of the needle? from the bottom?
so i moved the C clip one closer to the tip of the needle, thinking along the lines of this is what a shim would do.
While in there i also slotted the mixture screw and double checked if they were 2.5 turns out. no, more along the lines of 2.25. so adjusted them to 2.5, put the bike together, took it for a spin to warm it up...
GREAT no more sputtering, stumbling, feeling like the whole engine wants to fall apart at low RPM. (it felt like i could feel every explosion under me lol.) it didnt feel like it had any more power up top though...oh well...
park it and go to adjust my idle as i played with it to raise the throttle a bit while warming up but then it came up to 1500 warmed up....low the adjustment look over and what do i see? lol my TPS plug hanging. idiot
hook it back up and take it for another spin...holy **** batman! like a whole new bike.
shifting hard to second causes the front wheel to loft in the air now, where before it would stay planted, much more power across the range. i can now cruise at 2000 rpm and not feel like the bike will lurch or stop.
so shimming the needles solves tihs problem, but then again, most of you knew this....
reason i wanted to make this post is to get everyones terminology and knowlegde in one post.
what symptoms are caused by what, what modifications will cause what? what changes will affect what?
anyways, the above mentioned symptoms are caused by a leaned out mixture which shimming the needles solves....backing out the pilot also known as mixture screw will also improve this BUT the mixture screw will only change settings at low RPM.
we still need to clear up when people talk about the idjustables needles as to which clip from which side they are talking about...
anyways, post away with any and all knowledge, and then we will condense it, filter it out and make a sticky out of it....aaand GO!
If some of you guys remember i had a shop install a DynoJet stage I kit about a month ago....about a week later it started to stutter and stumble at low RPM (read below 3000) when warmed up...it was doing this before and i was hoping that the DJ kit would cure that...well, nothing.
Symptoms were:
1/8 to 1/4 throttle below 3.000 rpm the bike would stutter, jerk, buck. full throttle would clear it, as soon as it climbed past 3000 rpm, the symptoms would go away.
Random stalling at lights, sometimes when leaving a light it would just stall and die...leaving me no choice but to slip the clutch when leaving the light. otherwise i'd look like a SQUID with no clutch control
Throttle had an on/off feeling, very hard to moderate throttle at low engine RPM leaving me no choice but to be in a low gear/higher rpm during corners so the throttle would unsettle the bike.
So today i decided, after much reading, that shimming my needle might possibly cure my problem, OOR, adjusting the fuel mixture screw.
anyways, i pulled the carbs out, took apart the diaphragm and realized that DJ needles have grooves on it for adjustment, so happily i came here and people talk about 5th grove, 4th grove...bla bla bla, but nobody says measuring from which size? from the top of the needle? from the bottom?
so i moved the C clip one closer to the tip of the needle, thinking along the lines of this is what a shim would do.
While in there i also slotted the mixture screw and double checked if they were 2.5 turns out. no, more along the lines of 2.25. so adjusted them to 2.5, put the bike together, took it for a spin to warm it up...
GREAT no more sputtering, stumbling, feeling like the whole engine wants to fall apart at low RPM. (it felt like i could feel every explosion under me lol.) it didnt feel like it had any more power up top though...oh well...
park it and go to adjust my idle as i played with it to raise the throttle a bit while warming up but then it came up to 1500 warmed up....low the adjustment look over and what do i see? lol my TPS plug hanging. idiot
hook it back up and take it for another spin...holy **** batman! like a whole new bike.
shifting hard to second causes the front wheel to loft in the air now, where before it would stay planted, much more power across the range. i can now cruise at 2000 rpm and not feel like the bike will lurch or stop.
so shimming the needles solves tihs problem, but then again, most of you knew this....
reason i wanted to make this post is to get everyones terminology and knowlegde in one post.
what symptoms are caused by what, what modifications will cause what? what changes will affect what?
anyways, the above mentioned symptoms are caused by a leaned out mixture which shimming the needles solves....backing out the pilot also known as mixture screw will also improve this BUT the mixture screw will only change settings at low RPM.
we still need to clear up when people talk about the idjustables needles as to which clip from which side they are talking about...
anyways, post away with any and all knowledge, and then we will condense it, filter it out and make a sticky out of it....aaand GO!
06-07-2009, 01:31 PM
#2
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http://www.dynojet.com/pdf/1185.pdf
If you have a dynojet kit installed or not, but don't have the instructions see above link.
1st groove is closest to the top, 6th groove is closest to the point.
If you have a dynojet kit installed or not, but don't have the instructions see above link.
1st groove is closest to the top, 6th groove is closest to the point.
06-07-2009, 09:30 PM
#3
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Leaner is higher on the needle.
Richer is lowering the clip on the needle.
But dont forget most people blow it in choosing main jets, the needle is only a part of that equation.
Richer is lowering the clip on the needle.
But dont forget most people blow it in choosing main jets, the needle is only a part of that equation.
06-07-2009, 10:37 PM
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well the shop installed the jets, so not sure what they put in...
lets see whats left in the box...170, 175, 190 and 195
so 180 and 185 are missing
so with yoshimura pipes, shortened, and a new filter, too rich main jets?
lets see whats left in the box...170, 175, 190 and 195
so 180 and 185 are missing
so with yoshimura pipes, shortened, and a new filter, too rich main jets?
06-07-2009, 11:17 PM
#5
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mains are regulated by the needle profile and its height in the CV plunger.
So determine what needles (fun fun) they have in there, and its clip position.
Then armed with that knowledge, you can deduct from the size of the mains to see where the Lambda point is falling.
(Lambda = perfect balance of air/fuel @ your altitude and pressures)
So determine what needles (fun fun) they have in there, and its clip position.
Then armed with that knowledge, you can deduct from the size of the mains to see where the Lambda point is falling.
(Lambda = perfect balance of air/fuel @ your altitude and pressures)
06-07-2009, 11:23 PM
#6
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well the needles are DJ adjustable needles that come in Stage I kit and i have it on 5th from the top clip...it was on the 4th and running too lean as mentioned above.
does that help?
does that help?
06-08-2009, 12:25 AM
#7
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Ok you are going backwards with the clip. - err maybe not, depending on terminology you used.
Lower the clip on the needle to richen.
THe lower clip position raises the needle in its CV plunger, making the opening
in the main fuel circuit bigger.
If you are at the bottom and its too lean, you need the bigger jets. (or are air leaking)
but put the clips back in the middle after going up a jet size so you dont jump to far.
Lower the clip on the needle to richen.
THe lower clip position raises the needle in its CV plunger, making the opening
in the main fuel circuit bigger.
If you are at the bottom and its too lean, you need the bigger jets. (or are air leaking)
but put the clips back in the middle after going up a jet size so you dont jump to far.
Last edited by Circuit_Burner; 06-08-2009 at 12:47 AM.
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