jetting

[2k7z400]

alrite guys. i have a 2007 z400 wit a full yosh rs3 exhaust. i have the tec kit also..no lid on airbox. i started out with a 150 mikuni main. and the thing was wayyyyy to rich. it was bogging bad. so i went down and now im down to a 142.5. i tried all the jets in between also. and it still runs a bit rich. around the inside of the exhaust is black when you wipe your finger on it. the plug is black. ive tried adjusting the fuel screw but when i try to lean it out some it starts popping bad when you rev it and let off. when its coming down the rpms is when it does it. so if ne body has some info please let me know i need it bad. o and when i idle it up it runs rough.

[drzoo2]

Unless your super high in elevation (5000) or so, the 142 Mikuni should be just about right. You shouldn't have to lean your fuel screw. Make it fatter for the extra air. Most people at your stage swap out the 22.5 pilot for a 25. An adjustable needle is a plus.

Basically forget the main until your pilot and mid are correct. Your main is the last circuit in the system and depends on the other circuits to be on.

You have to tune it until the engine runs good with no popping in deceleration.

z

[2k7z400]

yea ive got an adjustable needle. its on the second clip from the top. and i have a 25 pilot but the stock 22.5 is in right now. should i go ahead and put in the 25?

[drzoo2]

Originally posted by 2k7z400
yea ive got an adjustable needle. its on the second clip from the top. and i have a 25 pilot but the stock 22.5 is in right now. should i go ahead and put in the 25?

What's your elevation?

I would put the needle on the third clip (counted from the top) and put the 25 back in. Put your fuel screw at about 1 turn. Warm the quad up to operating temperature.

To tune the fuel screw........
Raise the RPM to a high idle. Just turn up your idle screw. About 1800RPM. At high idle, slowly add turns to the fuel screw till the engine rpm drops (and nearly dies). Now, slowly turn the screw back out. You will hear the engine rpm begin to speed up and the exhaust note will become crisper.

Stop turning the fuel mixture screw at the exact moment when the engine hits peak rpm. Peak rpm is when the engine runs the cleanest and fastest.

You may have to add a quarter to a full turn if you pop on deceleration. Once you get this tuned I think you should be ready to fiddle with the main.

Start with a large main. One you know is too big like a 165. If your main is too fat, when you go from low-mid RPM to WOT there will be a slight hesitation. Keep dropping your main 1 size till this disappears. Once gone you should be set.

z

Thanks to Byte on central for the excerpt.

[2k7z400]

im at around 1100. yea ive tried that cuz im on central too but i must be tone def or somthing. but ill try again tommrow and see if i can get it closer. i did the exact thing with starting with a 152.5 and it was way too much black smoke out the exhaust so i kept on trying and now im down to a 142.5 and i think im close. just need to fine tune. theres still a stumble in the idle specailly at a high idle.

[drzoo2]

I'm at 1400 so your a bit lower than me. Here's my setup.....

Full FMF Ti-4 system
K&N Filter and Power lid
Old Style Hot CAMS
Stock Carb 150DJ main, 25 pilot, 2.25 turns air screw, Alba Needle 3rd Clip. Elevation 1400'

I found with the cams that I was fat before the install. I was originally running a 160DJ. After the install I had a hesitation. If your using a 142Mikuni we should be pretty close to each other.

If your fat you should see some black smoke but only when pinning it. From closed to 3/4 it should run good. If fat you should feel a hesitation. I wouldn't worry about your main till the rest feels good.

z

[2k7z400]

thats exactly when i see the smoke. its not near as bad as it was though. its alot closer for sure. and see i have a quadworks airfilter. which is the foam on the outside part and then a reg paper type filter under it. so i dont know if maybe your k&n stuff may flow better. i read on the central that really everybody under 3000 feet is gonna be close to the same and over 3000 they will be close to the same. with some exceptions of course. but you get the point. so yea ima put on my 25 pilot today and move back to 3rd needle i guess. and try it then.

[cataway]

Originally posted by 2k7z400
alrite guys. i have a 2007 z400 wit a full yosh rs3 exhaust. i have the tec kit also..no lid on airbox. i started out with a 150 mikuni main. and the thing was wayyyyy to rich. it was bogging bad. so i went down and now im down to a 142.5. i tried all the jets in between also. and it still runs a bit rich. around the inside of the exhaust is black when you wipe your finger on it. the plug is black. ive tried adjusting the fuel screw but when i try to lean it out some it starts popping bad when you rev it and let off. when its coming down the rpms is when it does it. so if ne body has some info please let me know i need it bad. o and when i idle it up it runs rough.
i find it hard to believe that you could not be lean ,i also have to wonder why your conserned about black smoke ,what does your plug look like ? ignore the smoke till it runs blue then you have a problem. some how some way get to a dyno !

[2k7z400]

because black smoke along with a black sparkplug usually means rich. so i just figured. ive been trying to jet this thing for right at a month now and i am getting fed up with it lol. and so are all of my friends because when they talk to me im usually messing with my z tryin to jet it right. im almost tempted to pay the stupid money and take it to this guy my dad knows who owns a motorcycle shop. he races and and works on pretty much any kind of cycle.

[Jon114xxx]

i have a z400 in frederick maryland with a full hmf exhaust and no air box lid and a big gun cdi.. ... what jet should i use? and does the no airbox make a considerable difference..

[drzoo2]

Originally posted by Jon114xxx
i have a z400 in frederick maryland with a full hmf exhaust and no air box lid and a big gun cdi.. ... what jet should i use? and does the no airbox make a considerable difference..

About the same as above. Removing the lid WILL make more of a jetting difference than just the exhaust alone. The CDI shouldn't play a factor. Only increases your spark energy and adds RPM. Follow the instructions above tuning your idle and mid. Once you've gotten those then play with your main. I think FMF recommends a 150Mikuni. Just remember that Dyno jets and Mikuni jet numbers are NOT equal. A 150 Mikuni is about the same as a 160DJ. One is size and the other is rated flow.

z

[drzoo2]

[i]because black smoke along with a black sparkplug usually means rich. so i just figured. ive been trying to jet this thing for right at a month now and i am getting fed up with it lol. and so are all of my friends because when they talk to me im usually messing with my z tryin to jet it right. im almost tempted to pay the stupid money and take it to this guy my dad knows who owns a motorcycle shop. he races and and works on pretty much any kind of cycle.[/B]

If the instruction I gave you already haven't gotten you in the ballpark, Then it maybe time for an expert to help you. You won't get any closer than using a sniffer to set your jetting. Make sure you get back to us and let us know where you landed. Also when using the plug to help with jetting your suppose to look at the bottom of the porcellin. Most people cut the threads off to see this.

z