!Carb jetting dang farnit!

[toby400ex]

Well, since i got my 400ex a few weeks ago ive been messing with the jetting to get it right. When i got it the main jet was a 165, which was so rich it fouled a plug everytime i started it. Then i went to a 155, which left the plug dark black and wet, now ive run a 146 for about 3 hours of riding, and it is a bit less black but it is still getting wet, so doesnt that mean it is running rich still. I'm tired of making the garage smell like gas and having to buy new plugs to get this shnit right. Right now I am running a 146 main with the screw out 3.5 turns and the clip at the 3rd groove, witht he airbox lid on , k&n filter and a slip on fmf pipe. Its set up for below 6000 ft according to my dyno jet kit. Should i just keep going down in jet sizes until the plug is the right color, i dont wanna screw anything up, but it doesnt foul the plug anymore and it starts perfect with great throttle responce, and oh yeah, i just removed the choke.

:confused:

[toby400ex]

hellllllooooo?

[toby400ex]

come on:mad:

[trailburner]

OK..first of all, I would call the person you bought the quad from. I don't think that this guy would have had the 165 main in the bike and have it running the way it was running when you first got it. I am running a White Bros. E-series K&N filter with lid off and mine runs perfect with a 165/160. The 146 main you have in right now sounds to small. Like I said, the best thing you could do is call the person you bought the bike from and find out what the bike ran like before you bought it w/ the 165. Then you will know if it is jetting or some other kind of problem.

Good Luck.

[wilkin250r]

Have you done the spark plug test at different rpm ranges and throttle positions? It's possible to be lean at 1/2 throttle, and rich at full throttle.

To test at different throttle positions, you want to run the quad at that throttle position, then check the plug. To do this, you hit the kill switch and pull in the clutch at the same time. This stops the engine without letting it throttle down. If your running too rich at idle and you let the engine slow down to idle before you check the plug, you will always read rich, even if it's lean at WOT.

To test pilot jet, ride the quad just above idle, then pull in the clutch and hit the kill switch. Pull the plug and check it.

For the needle position, ride at 1/2 to 3/4 throttle, kill the engine and pull the clutch. Check the plug.

Obviously for main jet size, do the same test at WOT.

[toby400ex]

hmm sounds like work:mad:

[jb400exxx]

what year is your quad? does it smoke at all, like when you start it up? my quad smokes for a second because my valve seals are bad. i thought my plug was black cause i was rich but it was because the oil was messin with it. i think the same thing is happening with yours. i have a 165 in mine and it runs great. a 146 sounds way to low, that's more lean than stock.

[JOEX]

I belive there is a difference in numbering of the Dyno Jets and stock Kehin jets...

Joe

[jb400exxx]

yea there is a difference and it's kinda confusing and get's really annoying. a 165 dynojet should work good for ya, a 160 at the lowest. idk about the regular keihn jets. i just use dynojets. a lot of people don't like the jet kits and just buy jets, i like havin the kit. next time you go to start your quad see if it smoke a little for a minute or 2.

[Houser Cannondale]

the good thing about the kit is they send you a new different needle also. the dyno jets are longer and sit down in the fuel more.

[JOEX]

Yeah, I would like to try a jet kit needle. I still belive (in therory) that the needle circuit is the most important...i gotta read more info:)
How does sitting in the fuel make it better? I'm not questioning you, just wanting to learn more;)

Joe

[jb400exxx]

when i rejetted mine a put the needle that came in the kit in the position it said to do, and i lost my quick throttle response so i put the stock one back in with the needle up one notch higher. now it runs great.

[toby400ex]

it doesnt smoke at all:eek2: , what is the stock jettin anyway, i thought it was 138 main:huh, its gotta just be rich or something, it is a 2000. And when i say the plug is wet, it is like real wet and gassy smelling:rolleyes:

[JOEX]

I don't have the "jet kit" but i raised my needle one notch and noticed a difference too. I should drop it back down to compare again though, just to see.
I do want to try a different needle though, just to see again:p

Joe

[toby400ex]

oh yeah, and the dyno jet kit says to set it the exact way that i have it set right not, so wtf

[JOEX]

Stock main is 148

[Houser Cannondale]

stock main is 122. im pretty sure. oh yea and are you just running the bike and gassing it or actually taking it for a litlte ride and warming it up to see how the plug looks?? that has a big diference.

[toby400ex]

this is a 400ex the main is like 138 i think, it is wet after i ride it for a while:eek2:

[trailburner]

Originally posted by JOEX
Stock main is 148
It is a 148 like joex said [i have a manual]....It's not a 138....

[toby400ex]

hmm, maybe the dynp jets are different, because 146 is what they recomend for the stage 1 and my elevation

[Houser Cannondale]

oh sorry i was thinkin of the 300. its was pretty early in the morning when i posted that. :rolleyes:

Isnt jetting fun :rolleyes: :)

Not everyone likes the Dynojets due to the difference from the Keihin numbers and flow changes from jets with the same numbers and also the little adapter.

Run what ever ones you like but know that many people who will talk about jet sizes are referring to the Keihin jets and have no reference to the dyno's your using.

You can also purchase "kits" with the Keihin jets and a jet board from many of the parts dealers, and you can get diff needles from Keihin also.

Do a search on jetting here and take a look around the net for some very good info. You can check out C&D site and I remember a some good info at Duncan and some of the other builders sites.

Sorry but there arent any easy answers to jetting and you need to set up each machine by trial and error thru a series of tests on each circuit (the guy who gave a list earlier is pretty much spot on in his suggestions) and then and only then will you know what jetting settings work best with your machine, and this will change again as the temps get warmer.

[Newbie400ex]

I have a 400ex w/ White Bros e-series, K&N air filter, and modified airbox lid. I'm at 298' above sea level. I run a DJ170 from the dynojet kit. People need to start putting the whole part number of their jets to help reduce all this numbering confusion. Mine runs great with the DJ170 in cold weather. I might go down to a DJ165 as it warms up. Another thing that could cause your problem would be the needle valve in the float bowl allowing the float bowl to flood. This could be what's causing the wet appearance of the plug.

[toby400ex]

Originally posted by Newbie400ex
I have a 400ex w/ White Bros e-series, K&N air filter, and modified airbox lid. I'm at 298' above sea level. I run a DJ170 from the dynojet kit. People need to start putting the whole part number of their jets to help reduce all this numbering confusion. Mine runs great with the DJ170 in cold weather. I might go down to a DJ165 as it warms up. Another thing that could cause your problem would be the needle valve in the float bowl allowing the float bowl to flood. This could be what's causing the wet appearance of the plug.
how would i fix that, im kinda new to working on carbs, so would that be the needle with the clips on it.:confused:

[Newbie400ex]

No. In the bowl where the fuel collects there is a float and needle valve assembly. When the fuel level is full the float raises up and closes the needle valve. This prevents more fuel from coming into the bowl until more fuel is needed. If this needle valve is not seating correctly. (dirt or old age) then too much fuel will go into the bowl (flooding). This may cause the excess fuel to be sucked into the engine making it run rough at idle and very rich otherwise. If the needle is old then you will have to replace it. If it is just a little dirty then a cleaning should do it.

[toby400ex]

i did notice some dirt in the bowl bolt/lid mobobber, so i guess there could be some dirt in their. The reason i find this all confusing is that the dyno jet kit tells what to do and i did it all. So i guess there is something wrong with it. Thanx for help.

[toby400ex]

ok, i finally pulled the carb out, again:grr . Ok so one of you guys were talking about the float needle valve i think. There is a thing that i can take out with a screwdriver then it has a hollow shaft with little holes in it, is that what you are talking about. Or is it the little plunger like thing that is connected to the floats.:confused:

[toby400ex]

bumpo:mad:

[toby400ex]

come one people, ive taken my carb apart and it seems that all the seals are good, and that float valve thing is good, but what exactly is the float needleor jet, is it in the float bowl, cuz it is clean as a motha:macho

The part your describing sounds like the slow jet (pilot) and should be right next to the main jet.

If you need the needle jet its on the other side of the carb.

The float and jet/valve is right by the float.

[Newbie400ex]

The little thing that is attached to the float is what allows the fuel to flow into the bowl. The thing the "needle" fits into is the seat. I'm not talking about the jet needle.

[toby400ex]

well the little thing connected to the float looks fine, actually like new or something, its all back together except i now have to find a tiny little washer that goes to a screw on top of the slide:mad:

[Newbie400ex]

oops :(

[toby400ex]

yeah, i know, what a pain in the *** a little washer can be. I bet i wont even be able to find a new one at any hardware stores:mad: