Dyno Jet problems

[RACER G3]

Hey Riders, I have a another jetting question that has not been covered in previous forums. I'm running stock bore 400ex engine with K&N filter, no lid, & White Bros R4 full system. I rejetted the bike according to dynojet (stage 2) and installed new needle, 170 jet, & 3.5 turns out on pilot screw, 3 grooves down on needle. The bike starts fine, idles well, but when I took it out for test ride it bogged down right at high rev position before shifting into second gear. Is the bike running lean or rich, and also should I adjust turns on pilot screw, up or down 1 clip, or change jet. I was told by Mechanic to chg to 165 jet and I'll try that, but what effect does moving clip up or down have on performance. I also get a little backfire too. Also I'm having issue lately that after riding the engines does not cutoff after turning off ignition & switch, anyone ever had this problem?

[cals400ex]

i would go get a 42 pilot jet and turn the fuel skrew out 3 turns or so. the larger pilot should help with the backfiring.

i agree, i would go down on the mainjet. i would actually go lower than a 165 though.

the needle clip position affects performance mainly from 1/4 to 3/4 throttle.

[RACER G3]

Thanks Cal for the reply, is the #42 pilot jet something I need to purchase. Dynojet instructions don't say jack about changing the pilot jet, they only refer to Main jet, needle, & pilot screw turns. I just got an email reply from Honda/Dynojet Tech Support and he suggested it may be rev limiter kicking in early. I'll do some test to check it and try the 42 pilot & then upgrading rev limiter. thanks once again, and keep shiny side up.

[cals400ex]

oh, i thought you meant backfiring on deceleration. the fuel screw is just a fine tune adjustment for the pilot jet. so, if you get a larger pilot jet, you won't turn the fuel screw out as far. the fuel screw technically isn't suppose to be ran at 3.5 turns out according to some engine builders. they say if you need to go more than 3, get a larger pilot jet.

the pilot isn't manditory, however it will make the bike easier to start and should reduce the backfiring on deceleration. i don't recommend getting a rev box unless you have motor mods. the box won't do much for you. also, the extra rpms that the box will give will just be tough on the vavle springs and the rest of the bike. when you start jumping into the motor, yes the rev boxes do help out. however, it is still harder on the motor.

rule of thumb:
the pilot jet and fuel screw mainly controls fuel flow from idle to 1/8 throttle. the needle diameter, taper, and clip position mainly control fuel from 1/8 to 3/4 throttle. the mainjet controls fuel flow from 3/4 to full throttle. when jetting you need to pay attention to the throttle range, not what gear or how fast your going. how far the throttle is pushed in is what matters mostly.

[F-16Guy]

Do not use their jetting chart; I think their secretary drew that up on her lunch break. With your mods, drop down to the 142 and see how that runs. If it's still boggy on top, try the next size down. If it gets worse, go the other way. I had similar mods (except a slip-on e-series), and I ran as low as a 138 with the airbox lid on and at high elevation. I'm pretty sure I ran right around a 142 with no lid in Phoenix.

[ewalker302]

You are way way rich w/a 170.

With just a pipe/filter lid off you should use a 146--148 DJ main.

:bandit:

[RACER G3]

Thanks again Cal & F-16 for your advice, I worked on the bike last night, dropped down to a 155 MJ and still had problems at 3/4 to WOT, I even shifted earlier to see if this made a difference, no go, still sputtering and you could smell gas at idle from it still being too rich. I got furstrated and went back to stock MJ 148 & 2.5 turns out on pilot screw, I ran a lot better but @ 3/4 to WOT same problem, The one thing I didn't chng back to stock was the needle, and I'll do that tonight. I just feel with the stock settings I'm not getting the full power from the mods, plus I paid $45 for the kit. I haven't given up yet, but I'm ready to ride it stock until i can figure it out or pay a mech to do it. It really doesn't seem that hard of a process, but a lot of trial and error. Also where's a good place to buy 42 pilot.

[cals400ex]

are you sure your not nailing the rev limiter? you can get the pilot jet from C&D, local dealer, etc.


yeah, put the stock needle back in if your going to be running keihin mainjets.

[RACER G3]

Cal when you say nailing rev limiter, are you referring to 3/4 to WOT, this is happening before I'm at max RPM for that gear. I'm not riding the bike any differently than before, and the rev lim never cut out like this. Also in the garage you can smell gas odor from tailpipe (rich). I saw a post for stock settings and it ref'd 2.25 pilot turns out. When I put the 148 MJ back in I reseated and turned it out 2.5 turns. Will this be a noticable difference in performance or will the bike be a little rich, also have you ever chgd needle with carb attached. I checked some prev. post and I noticed that you suggested to speedydog to run a 152 MJ w/2.75 turns out with a T-4 slip-on with lid on. would this be a good settings for the WB R4 full system w/lid off.

[s-10s_rule]

That ^ seems more like what you need, I have a 416 as stated below and I run the stock needle position, 165 main jet and just tinkered with the pilot screw, so I don't know exactly where it is, but I do have the stock pilot jet too. This works great for me, so I doubt that you'll need to mess with the needle from the stock position and I'm pretty sure a 155 main jet will work fine, that is what all of my buddies run in their 400s and they have about the same mods you do, just different brands, none of them seem to have a problem. Also they have the stock pilot jet. A 155 to a 148 is probly the range you'll need. PS, make sure that the choke is all the way open and your float is set correctly. Also make sure that you dont have any air leaks anywhere and that your getting plenty of fuel to the carb from the gas tank. Kinda sounds like one of those things could be throwing you off. Good luck.

[cals400ex]

Originally posted by RACER G3
Cal when you say nailing rev limiter, are you referring to 3/4 to WOT, this is happening before I'm at max RPM for that gear. I'm not riding the bike any differently than before, and the rev lim never cut out like this. Also in the garage you can smell gas odor from tailpipe (rich). I saw a post for stock settings and it ref'd 2.25 pilot turns out. When I put the 148 MJ back in I reseated and turned it out 2.5 turns. Will this be a noticable difference in performance or will the bike be a little rich, also have you ever chgd needle with carb attached. I checked some prev. post and I noticed that you suggested to speedydog to run a 152 MJ w/2.75 turns out with a T-4 slip-on with lid on. would this be a good settings for the WB R4 full system w/lid off.


rev limiter is the max rpm the stock cdi box will enable you to go too. in your garage it is quite possible to smell exhaust. when your bike is running in your garage, you will smell burnt exhaust. i wouldn't necessarily say the jetting is rich just because you can smell it. with the slip on and air box lid off, i would try 3 turns out on fuel skrew, 155 keihin mainjet, and needle clip in the factory position. just remember, the stock needle and mainjets are both different from the dynojet needles and mainjets. so a 155 keihin is NOT the same as a 155 dynojet.

[F-16Guy]

The DJ jets seem to be numbered differently; the number is supposed to be the orafice diameter in thousandths of an inch, but it might not be with the DJ jets. Try the 142 main with the needle where the instructions say. You are using the DJ main jet adapter, right? Also, check to make sure your throttle cable is adjusted properly. It sounds stupid, but the slack sneeks up on you. Just turn the adjuster on the thumb throttle housing until almost all of the slack is out (should be about 1/8-3/16" play on the lever).

[dariusld]

Originally posted by RACER G3
Hey Riders, I have a another jetting question that has not been covered in previous forums. I'm running stock bore 400ex engine with K&N filter, no lid, & White Bros R4 full system. I rejetted the bike according to dynojet (stage 2) and installed new needle, 170 jet, & 3.5 turns out on pilot screw, 3 grooves down on needle. The bike starts fine, idles well, but when I took it out for test ride it bogged down right at high rev position before shifting into second gear. Is the bike running lean or rich, and also should I adjust turns on pilot screw, up or down 1 clip, or change jet. I was told by Mechanic to chg to 165 jet and I'll try that, but what effect does moving clip up or down have on performance. I also get a little backfire too. Also I'm having issue lately that after riding the engines does not cutoff after turning off ignition & switch, anyone ever had this problem? Alot of people in this site bad mouth Dynojet or blame their problems on their jet kit. I installed my exactly as you did and it ran strong without any other adjustments. It was probably a little rich, but I rather have that than lean because I do all desert riding. I have also bought the individual jets, that worked too and cheaper. I think people have a problem and the easy blame is the jet kit.

[RACER G3]

I really appreciate all the advice from members, I wanted to do it myself to have an idea of how to do it. I'm pretty much at the end of the line and will have to pay mech to complete. Last night I chgd needle back to stock (3rd groove), MJ back to stock (148), and 2.5 turns out. The bike runs better, but it starts to bog down in mid-throttle position, rich or lean got me. I by no means are trying to bad mouth DynoJet, I just need my bike running the way it was or better, it's hard for me to have confidence in taking a jump or hill when I can't blip throttle or WOT for steep hills. My only last adjustment I will try is turn pilot screw out 3 turns w/stock jets and needle. Thanks, I checked for air leaks, and when I chgd Dyno needle I noticed washer was not seated, but the stock one does not have washer and it still runs poorly. So I really don't know what the problems is.

[cals400ex]

i am wondering if the problem is something else. the bike should run fine.

[ewalker302]

Just FYI the pilot screw wont do anything for your problem it's just for fine tuning the pilot circuit which only affects idle to 1/8 throttle. The washer that comes with the DJ needle is for making 1/2 clip adjustments-----If you put the washer under the clip it raises it 1/2 of one position.


Just thinking here, but after going back to stock settings and still having probs, the only thing I can think of is that the engine may not be getting enough or too much air. I would check the intake tube going from the airbox to the carb for a restriction or a cut or tear in the rubber, I don't know if a leak in the intake seals or intake tube (too much air) would make it bog like that or not. I'm sure it's not, but if the filter is really dirty?????


Also, have you checked your spark plug since changing the 170?????
:bandit:

[RACER G3]

It's really weird, but It's not WOT that I have the problem it's around 1/2 throttle position. I putted around with my wife while she was riding and I noticed after 1/2 throttle is where I'm getting the bog, not sure if it's too much gas or air?. My buddy also suggest spraying WD40 to check for air leaks, we'll try that this weekend and listen to see if engine sputters. I'll also check for slack in throttle cable, didn't touch it but you never know. I beleive it to be something else causing problem, maybe boot is cracked due to the fact that I've removed the carb 5-6 times. Also to other riders, there are short cuts to removing plastic front every time you make a adjustment, the carb can be removed by taking gas tank cover, gas tank, and disconnect fuel/air lines and slide gas tank to the rear to remove, carb is accessible after those items remove, also you can take 17mm socket and unscrew screw under carb and remove MJ from bottom and replace. The one thing I would like to see is knob on the pilot that you can adjust by hand and fine engine easier. Saturday I have a racer/mech friend of mine coming over to help solve problem. Thanks once again to all of the suggestions. I'll keep you posted on Monday. What should I look for with spark plug, color, moisture, I didn't check it before changing to 170 MJ (Dyno), but I will this weekend and maybe chng that too.

[s-10s_rule]

Haha, I have an Idea, make sure that your accelerator pump is working properly. I fixed my buddies Warrior by freeing up his accelerator pump cylinder, and it was a really weird thing since they are only supposed to make a shot of fuel when you mash the throttle but on his you couldn't get it past 1/8th throttle without it bogging no matter what you did. So I would check that by making sure your getting a shot of fuel in the carb when you push the throttle. You can probly hear it with the machine off and putting you ear close to the carb. If you arent make sure all the passages are clean and the cylinder for the pump is moving freely.