rejet a 400 after doing a 440 kit?

[EX LONERIDER]

not sure but do you rejet a 400 after doing a 440 kit? not sure if there is a need for it or not but figure i'd ask. im at sea level elevation and ride at the dunes around glamis, buttercup, ogilby, and gordon's.

i beleive i have a 148 main in it right now and a stock pilot. thought i would go up to a 40 size pilot and a 155 main. what do you guys think?

[casey_lamm]

alot of people say a 42 pilot, im waiting to here from so others with the that. Why is a 42 almost always recommended.


Originally posted by EX LONERIDER
not sure but do you rejet a 400 after doing a 440 kit? not sure if there is a need for it or not but figure i'd ask. im at sea level elevation and ride at the dunes around glamis, buttercup, ogilby, and gordon's.

i beleive i have a 148 main in it right now and a stock pilot. thought i would go up to a 40 size pilot and a 155 main. what do you guys think?

[Sparky_20]

Put in a 42 if you have problems starting, a 40 may even cure that. What other mods do you have besides the 440? I'd start a bit higher than 155 if you have a full exhaust, cam and intake. Maybe a 158, start there and see what happens. Im running a 155 main with just a slip on and a uni

[EX LONERIDER]

well, besides the 440, it has a 11:1 comp ratio in it, sparks advance key, stage 2 hotcams, mild port work, ported and matched intake, choke removed from the carb, big gun full system, about 1 3/8" hole drilled on the top lid of the air box, K&N.

i also ride at sea level elevation. gordon's well area in specific.

i dropped in a 155 main for the time being and see what happens. if its too lean ill drop that and go up to the next jet. it didnt have too hard a time starting with a 38 pilot. im in fair weather climate so starting is not too hard.

[Sparky_20]

im pretty sure your gonna need a bigger jet than that with those mods. Try a 158 or 160 to start.

[davetheslave]

I had a DJ 175 in my bike with basically the same mods and I'm at 4500 feet. I would bet your gonna need to be a little bigger on your main.

[EX LONERIDER]

thats weird. when i had it previously jetted for an exhaust and filter kit, the bike aways ran on the rich side. plug had a darker brown shade to it but it always smelled a bit on the rich side. im using the K&N filter package jets that they provide. i followed their instructions and also installed a new needle that came with the kit originally. im wondering if the combination of these things make it run just right as it was.

the bike never got hot, had great acceleration and even some of my buddies said that i used to run rich so i leaned it out some on the mixture screw. :confused:

wonder if the altitude i ride in has alot to do with it. ill give a few runs on it and check the plug and see what happens. ill know if im off on the jetting immediately.

[400exrider707]

Jetting for a pipe or filter is a little more straight forward once you change engine parts like the piston, you could alter your vacuum pulse to the carb, the vacuum from the motor might pull harder and then pull in more fuel, I have seen people go to big bores and have to drop their jetting sizes, because the vacuum pulse was so much greater.

[GPracer2500]

Originally posted by EX LONERIDER
....im using the K&N filter package jets that they provide. i followed their instructions and also installed a new needle that came with the kit originally....

K&N jet kits are re-badged Dynojet kits. Their mains use a different scale than Keihin main jets. A 155DJ has approximately the same size orifice as a 170K.

[EX LONERIDER]

Originally posted by 400exrider707
Jetting for a pipe or filter is a little more straight forward once you change engine parts like the piston, you could alter your vacuum pulse to the carb, the vacuum from the motor might pull harder and then pull in more fuel, I have seen people go to big bores and have to drop their jetting sizes, because the vacuum pulse was so much greater.

i didnt think anyone would understand what i was talking about if i said what you just said but yea. i figure with a bigger displacement it creates a bigger vacumme effect so it'll have a tendency to drag in more fuel as it is. i wouldnt be all too surprised if that was the case.



K&N jet kits are re-badged Dynojet kits. Their mains use a different scale than Keihin main jets. A 155DJ has approximately the same size orifice as a 170K.

ok... thats good to know. for right now, i have a 38K and a 155DJ. ill have to mess with it some i know tho thats the base lines from what i found in the searches i made for this modification spec. i havent lit it off yet to do the break in so ill know whats up soon as i can run it up the street some to give a better rundown of how its gonna run.

[REDRIDDER]

Originally posted by 400exrider707
Jetting for a pipe or filter is a little more straight forward once you change engine parts like the piston, you could alter your vacuum pulse to the carb, the vacuum from the motor might pull harder and then pull in more fuel, I have seen people go to big bores and have to drop their jetting sizes, because the vacuum pulse was so much greater. NICELY SAID

[EX LONERIDER]

ok... so i lit it off a while ago for the initial cam break in and it sounds wicked. currently it wont idle tho. i think the idle adjustment is funky but i also think its slightly on the lean side at idle. im thinking i can adjust the fuel mixture screw and richen it up but im wondering how much?? what do you guys suggest?

by the way, to all who have responded with help, thank you very much.

[casey_lamm]

Do it run well 1/2 to wide open? if so then consider changing your pilot jet.

The fuel mixture screw will allow you to richen it up, but that might not be the best solution if it runs well on the higher end.


Others: since im also new please correct me if im wrong.
Originally posted by EX LONERIDER
ok... so i lit it off a while ago for the initial cam break in and it sounds wicked. currently it wont idle tho. i think the idle adjustment is funky but i also think its slightly on the lean side at idle. im thinking i can adjust the fuel mixture screw and richen it up but im wondering how much?? what do you guys suggest?

by the way, to all who have responded with help, thank you very much.

[GPracer2500]

Originally posted by casey_lamm
...The fuel mixture screw will allow you to richen it up, but that might not be the best solution if it runs well on the higher end...

The mixture screw (aka pilot screw, aka fuel screw) is part of the pilot circuit--it's job is as a fine-tuning point for the pilot circuit. There's a thread in the "How To" section that describes the relationship between fuel screw settings and pilot jet sizes.

The fuel delivered by the pilot circuit does contribute some amount to the total fuel delivered when "on" the other circuits. But the contribution of the pilot circuit is thoroughly overshadowed by the main jet at larger throttle openings. Nonetheless, when fine tuning the jetting it is generally good practice to get the pilot circuit correct first....then move on to the other circuits.

[casey_lamm]

cool so I was 98% right. I will take that!
Originally posted by GPracer2500
The mixture screw (aka pilot screw, aka fuel screw) is part of the pilot circuit--it's job is as a fine-tuning point for the pilot circuit. There's a thread in the "How To" section that describes the relationship between fuel screw settings and pilot jet sizes.

The fuel delivered by the pilot circuit does contribute some amount to the total fuel delivered when "on" the other circuits. But the contribution of the pilot circuit is thoroughly overshadowed by the main jet at larger throttle openings. Nonetheless, when fine tuning the jetting it is generally good practice to get the pilot circuit correct first....then move on to the other circuits.

[EX LONERIDER]

awsome guys, thanks! yea, i read up on that "how to" in the articles section and am starting to understand it better now that you cleared that up.

as of right now i need to slap my boot, box and filter on as i think its running lean due to the flow. (i had a severly dirty filter so i took it off meanwhile i broke in the cam)

i still have a couple more run in times before i can run it up the street. once i do i will report back to you guys as to what it did. it seems to run fine but its all a insuficient reading cus of the intake being off.

[EX LONERIDER]

ok, so i placed all the intake stuff back on and lit it. idles fine, alot less heat due to the correct air flow now. (richened back up)

so i start running it around the back yard some (large back yard) slowly to load and unload the motor some. now, what i found out is the throttle response is pretty dead on. however, as i let off especially cut the throttle, i get quite a bit of "popping" comin out of the exhaust. i sum this up as a lean out when the throttle is cut correct? my question here is;

is that normal and i should leave that be, or do i richen up the idle circuit some to preven the lean out?

[GPracer2500]

Originally posted by EX LONERIDER
ok, so i placed all the intake stuff back on and lit it. idles fine, alot less heat due to the correct air flow now. (richened back up)

so i start running it around the back yard some (large back yard) slowly to load and unload the motor some. now, what i found out is the throttle response is pretty dead on. however, as i let off especially cut the throttle, i get quite a bit of "popping" comin out of the exhaust. i sum this up as a lean out when the throttle is cut correct? my question here is;

is that normal and i should leave that be, or do i richen up the idle circuit some to preven the lean out?

Some popping on decel is normal. When there is a complete absense of popping on decel no matter what you do to try and get it to pop then you're usually richer than ideal on the pilot cirucit. This can vary depending on the carb type (and is one reason why the subtle changes in exhaust popping is not the best way to tune a pilot circuit).

If it's an annoying sound or rapid-fire machine gun like sound, then it should be addressed. Try turning your fuel screw out a 1/2 turn and see if that provides relief.

If it is minor then don't worry about it--just tune the pilot circuit using fuel screw reaction as your guide.

Also, make sure your headers are sealed well to the head. Use fresh crush gaskets if you've re-used the ones that are in there now. An air leak in that area can cause popping that has nothing to do with the jetting.

[EX LONERIDER]

Originally posted by GPracer2500
Some popping on decel is normal. When there is a complete absense of popping on decel no matter what you do to try and get it to pop then you're usually richer than ideal on the pilot cirucit. This can vary depending on the carb type (and is one reason why the subtle changes in exhaust popping is not the best way to tune a pilot circuit).

If it's an annoying sound or rapid-fire machine gun like sound, then it should be addressed. Try turning your fuel screw out a 1/2 turn and see if that provides relief.

If it is minor then don't worry about it--just tune the pilot circuit using fuel screw reaction as your guide.

Also, make sure your headers are sealed well to the head. Use fresh crush gaskets if you've re-used the ones that are in there now. An air leak in that area can cause popping that has nothing to do with the jetting.

yea, it was nothing bad, but then again, i only decel'd for a second or two. ill try and see what it does under normal decel (long period). ill check into the header gaskets as well. i just placed new crush seals when the head was off. ill make sure they sealed. thnks for the advice, i appreciate it.