oh no!!, yep another jetting question

[bmf400ex]

just got a 2000 400ex and i know nothing about them, its all stock except for a maybe full or maybe slip on t-4 Pro Circuit pipe, can't tell if its stock header or not, but it does have the light rusty look to it. guy i got it from says its got full exhaust, but it does have a k&n filter, no air box lid and he says a jet kit with bigger pilot. i dunno how true that is but its definitley runing rich, plug is black and wet as ****, it fouled it yesterday when i tried to start it.

anywho, i traded my freshly built ground up 87 LT500R for it straight up, assuming i have a full exhaust my question is no matter whats in it now what size pilot, and main should i run along with needle clip setting with no airbox lid. if i need a jet kit i will buy one, i don't care whats in it now, i will get whatever i need. i live in central indiana for u atmospheric pressure gurus.

i can say that the quad runs great the way it is, no coughing or missing, but off idle (which it doesn't very well) its a little abrupt and feels like there should be more low/low mid umph there. like i said the plug was black and wet.

any advise to get me in the ballpark

[bmf400ex]

T T T

[Texan32]

first things first. Get a new plug. The old plug may just need replacing. As far as jetting....whats the elevation where you are?
If its below 2500 is ft. start with this. The pilot jet should a 40 (or 42 if your in really cold weather) with the mixture screw set at about 2-1/2 turns out. For the main jet, i would say somewhere between a 160 and 165. I would initially set the needle clip in the middle. Not many guys here have to move the clip. Factory setting (3rd knotch down) seems to do ok for most people.

Have you even pulled your carb apart to see whats in it?

edit: how are you doing a plug check? Holding a constant rpm and then shutting it down? Letting it idle for a while then checking? Or just cruising arould for a while and looking? Because of different addatives in gas, its hard to get a true reading, but the throttle position last held when checking the plug make a difference

[AtvMxRider]

If it is a pro circuit pipe it will have 2 springs on the pipe where the stock heat shield would be. I would try a 160 main and a 42 pilot.

[bmf400ex]

no, i haven't looked in the carb yet, and my plug check was after i tried to start it and it wouldn't. i am approaching this as if it was stock carb, so i don't care whats in it, but keep in mind that i am running with no airbox lid and i don't have one to put on it.

oh ya, the stock shield is on there, but i will have to look and see if there is springs behind it.

[AtvMxRider]

The stock shield won't work if it is Pro Circuit unless it has been modified so it should be a stock pipe.

[bmf400ex]

well the guy i bought it off of wasn't the sharpest tool in the shed. i thought the header looked stock, so anyway with just a slip on should i go with the (all keihin) 160 main, 42 pilot, and the 3rd position clip, and all this HAS to be with the lid off and a k&n filter, cuz thats all i got to work with.

[Texan32]

I could be wrong, but i thought the complete system does NOT use the heat shield. The jetting ideas i gave are for no air box lid. I would definately get a new plug though!

[AtvMxRider]

(I could be wrong, but i thought the complete system does NOT use the heat shield.)


You're right it doesn't there is no place for it to mount.

[bmf400ex]

with two (don't think so's and my own self doubt) i am gonna say i officially just have a slip on, so tonight i am gonna pick up the 160 main and a 42 pilot, and i am gonna take the choke off. does the lid off make a big difference on these 400's, cuz it seems it would run way lean with it off, oh well , these jets are a good start.
thanks for the replies, can't wait to leave work so i can get home and get started. OH ya, i gots plenty of Fosters to keep me hydrated whilist in the garge.:D

[Texan32]

there is NO problem running without the lid. You just have to run a little richer than with it on, but the suggestions i gave were intended for the lid being OFF. I would HIGHLY recommend getting an outerware for you K&N though. The K&N is a HIGH flow filter. Consequently, it lacks the ability to stop tiny dust particles from entering the motor. The outerware will prevent this from happening! It also propels water....

[bmf400ex]

i already planned on getting one, but i am trying somewere to buy it, along with oil and other goodies. i can find all of what i want just not at the same place. main problem being i want Klotz tranny oil.

[BornOnFire]

While you are at it, you may want to check the throttle cable adjustment. That can give you a little more of the response that you seem to be missing. The throttle comes from the factory with way too much slack. Do a search on here and you'll see what I am talking about......

[Sportrax 400EX]

My setup is close to yours. I had the same exact problems. Decent pull up top but low end sucked and ran to rich. If your below 3000ft like I am (If I'm thinking right Indiana is about 700ft above) this is a perfect setup. Trust me I just spend the last few weeks talking to EVERYONE and trying many different setups on the jets. In the end this is what I found to work best. It now has great pull off the line and can keep the wheels off the ground through 3rd..... I have my airbox on so my Main jetting is #146. The following should be perfect on yours with the lid off. I ran this setup with my lid off and it was right on the money. I had to put it back on because I ride through creeks. Here it is:

Main=Dynojet brand #160-#165 with Dynojet adapter
Needle=Dynojet needle on #3 clip position
Pilot Jet=Use the Stock Honda #38 jet (available at dealer if you don't have it)
Air Screw=3.5 turns out.

Try this out and install a new plug. I'm sure you will see better low end power and the plug won't be fouling out and black. If your running just a bit lean turn the air screw in 1/2 turn. Jet sizes are different with different companies. The numbers I gave you must be Dynojet brand. You might want to order a jet kit (#Q107) from them to be sure you have the right stuff. When installing the jets be sure to use a wide flat blade screw driver that fills the whole slot on the jet. They bend easy when you tighten them down. A large flat tip screwdriver will help prevent this. I ended up going out and buying one with the jet in hand to get a perfect fit.

The main thing that will help you is getting the stock #38 pilot jet back in. Most rich conditions are because the pilot is to large. Unless you have heavy mods the pilot should stay stock. You can use the air screw to fine tune the pilot circuit. If your finding that you have to have the pilot screw in almost all the way to get the mixture right then that is when you need to up one size on the pilot. Usually that is only needed with heaver mods. One thing, make sure when turing in the pilot screw you don't tighten it up hard. Just turn it in until it seats slightly then make your 3.5 turns out (counter clockwise) from there. If you find your running lean turn the screw in more if you find your running rich turn it out more.

Give this a shot I'm sure you'll be happy with it. Let me know how it works.

D.

[bmf400ex]

last night i put in a 160K main, and a 42 pilot, i also took off the choke, it starts much easier now. i have not rode it yet so i will test it tonight, i should have my new twist throttle in friday, so any other carb tunning i will do then since i have to put the new cable on. i also just changed the oil and filter so its all ready to go. i hope to get this all tweaked out within the next two weeks because i am going to Haspen Acres in Lorel, IN. Thats the best place to go ride in the state with over 800 acres with an mx track and a drag strip.

but i do have a question, what does the adapter look like for the main jet, because when i put mine in it looked like i was installing it on top of another main jet. Is that a Dynojet adapter or is that what its supposed to look like?

[Texan32]

yes, that is what the dyno adapter looks like. Not including the threads, the factory jet is about 1/2 inches long. The dyno (again, not including the threads) is only 1/4 of an inch. So, they give you that adapter to make it longer. In all honesty, i don't see why its even needed. I rejetted my buddies 400 with my leftover jets from a kit i baught. We didn't use the adapter in his and it wirks just fine!

Anyhow, i'm still thinking a 160 is going to be too rich for having a factory muffler. But, i hope it works well enough for ya

[Sportrax 400EX]

Yea I know what you mean when you say it looks like it's going to be to tall and your on top of another jet, well actually you are. The stock main jet sits on top of the needle jet. You remove the stock main jet then install the adapter where that was and the new (smaller) Dynojet main jet into that.

[bmf400ex]

so if thats the dynojet adapter i will definitely have to take it out, cuz i just wanna run the 160k jet that i have. i should have taken it out last night, so that means it prolly has the dynojet needle in there too! will i have to leave the adapter in there or will the dynojet needle work just fine with the keihin jet.

[Sportrax 400EX]

I must have missed that you have a stock exhaust. If so don't use the 160-165. Go with a 146 (Dynojet) and try it out. If it's to lean on the top end of the power band then use a 155 main (Dynojet). My bet is you'll see best results with the 146 main. Remember the Main jet circuit only controls flow from about 3/4 throttle and up. Pilot and air screw handle off idle and and up to about 1/4 throttle. Mid range is mostly affected by the needle.

[Sportrax 400EX]

If it were me I'd get a new Dynojet jet kit if you can't verify what jets/needle are in there now. If you start fresh you'll know what you have in there and it will be far less headache and work in the end. Main thing, to see better low end performance is to get that #38 stock Honda pilot jet back in there. Just my opinion.

D.

[bmf400ex]

no , i have a pro circuit pipe not stock, and i want all keihin in there. i just wanna know if the dynojet needle will work with stock jet without the adapter? i know its not tapered as much as stock needle but thats ok, it will act as if theres a little larger main in there. i will find out for sure if it has a stock or dynojet needle fri or sat.

[Taco]

If you dont want anymore headaches and you want to run keihln jets go ahead and make sure you dont have the dynojet needle in there. Im currently running a 42 pilot jet needle clip down a notch (4 down i believe) and a 160 main with a outerwears airbox cover.

[bmf400ex]

is there any easy giveaway to tell the difference between factory and dynojet needle.

[Sportrax 400EX]

Not that I know of except that the stock taper is larger. There might be number differences on it but I'm not sure what they are. If you plan to use all keihln jets check with them to see what numbers are the equivilant of the Dynojet numbers I gave you. They differ between the two brands. The dynojet numbers won't apply to the keihln ones. Are you planning to use the stock pilot jet though?

D.

[bmf400ex]

no i am sticking with the popular 42, which i just put in and seems most excellent on startup and i no longer have a choke.

[Sportrax 400EX]

Test it out and see if it still fouls the plug. I was at 42 and 40 and every main you can think of over the last few weeks and still had poor response. Went back to 38 and like magic the power was back. Very snappy off idle response and great pull off the line. I'm running a vented airbox lid, Full Big Gun exhaust and K&N filter with OW. Keep us posted on how it turns out.

[Texan32]

sorry about the factory muffler comment....thinking of a different post...

Anyhow, i think sportrax might be on to something about the jet #'s. I don't know if Keihn and dynoet sizes are the same. About the needle....the dynojet needle does have a more narrow taper...this allowes for increased midrange. But there isn't enough of a difference between factory and dyno to see with the naked eye. Also, if you are using keihn jets, you will need to take the adapter out of the carb

I'm not really sure why sportrax is so adiment about using the 38 pilot. I HATED starting my 400 with the 38. Since i put in the 42...3 pumps on the throttle and she fires right up. I don't know what kind of riding he does where 1/4 throttle is SOO important...just curious

[bmf400ex]

Originally posted by Sportrax 400EX
Test it out and see if it still fouls the plug. I was at 42 and 40 and every main you can think of over the last few weeks and still had poor response. Went back to 38 and like magic the power was back. Very snappy off idle response and great pull off the line. I'm running a vented airbox lid, Full Big Gun exhaust and K&N filter with OW. Keep us posted on how it turns out.

unless it runs like total crap i am sticking with the 42 pilot because of cold winter with average in the high 30's around here. so i will concenterate on the needle and i will take out the adapter if i have enough time tonight.

[Sportrax 400EX]

Mine fired right up and idled perfect with with the 42 also. I saw harder starts with the 38 until I fine tuned the pilot circuit and now it fires right up with 2 pumps. Idle is perfect at 1400RPM. Even when it sat for two days i came out pumped it and it fired up and never cut off. Might just be me, every quad has it's differences.

D.

[Sportrax 400EX]

I do some dragging with mine so off the line power is key.

[Sportrax 400EX]

I'm not saying the 38 is the best option but if all else fails try it you might be surprised. I know I was. After weeks of trying stuff I finally tried going back to it after a few members and Dynojet recommended it and loved it.

[bmf400ex]

the dude i got this off of had a 58 pilot in there and a keihin 158 main with the dynojet adapter in there. i can't believe it ran as good as it did.

[Sportrax 400EX]

Wow, now I know why the plug was black :)