can't get rid of the bog..

[darkzealot]

Ive been reading many post to help me and ive been rejetting/adjusting the a/f screw at least 5 times, but i can't get rid of the hesitation when i stab throttle from idle.

I just built my 416, JE 10.8:1, hotcam stg 2, a rev box, uni filter with lid off and yoshi slip-on. Elevation is about 150 feet and temp is around 20-25 degrees °C. I'm currently running a 170 dynojet with needle on 3rd clip and 42 pilot, a/f screw 2 turns out.

I started with 42 pilot, a/f screw 3 1/2 turns out. I though it wasnt getting enough fuel, so i went with a 45, a/f screw 2 turns out. No success. tried 1.5 turns out, no success. i went back on the 42 a/f screw 2 turns out but with the needle clip on the fourth notch. Engine was running like crap, jetted too rich. So now im back on the setting i wrote above.

With every setting : i got that hesitation from idle to full throttle. ( and i tried it in neutral, somtimes it will die from the throttle stab, sometimes it will bog a sec ) the exaust pops on deceleration,( with the 45 pilot, it seemed better when the engine was hot, didnt notice with the 42 ) Engine idled pretty good on every setting i tried . I have no other problems, just this anoying bog.

Plz help me, i really dont know wats the problem...is this a sign of lean or rich pilot circuit ? Thx !

Post is kinda long, but you should have everything to help me with that =P

[kilgoja]

stay with the 42 pilot...i haven't heard of anyone using the 45....too rich.....lower ur main jet to like a 165 or 160 and try that......i'd say set the a/f needle 2 1/2 turns out or 3 1/2 if that is too lean

[darkzealot]

hmmm..i could be wrong but i dont think main jet is causing the bog..? And ive tried 42 pilot with 2 turns out and 42 with 3 1/2 turns out...alway had that anoying hesitation. Thats what im trying to fix before i get into the main jet tuning.

You are probably right though, 170 dyno is probably rich.

Any1 else to help with the hesitation when i stab the throttle from idle ?

thx you =)

[darkzealot]

any1 else ?

[GPracer2500]

Is the accelerator pump working?

[darkzealot]

how can i check that ? =P

[dariusld]

Originally posted by darkzealot
how can i check that ? =P

I don't know the real way to check it but take off the filter side to the carb off and stab the throttle and see if its squirting out that tube inside the carb. I have the same main jet as yours, but a stock pilot jet and it runs fine. Maybe you just need a 450:devil:

Maybe its not the jetting. Maybe it has something to do with another part of the rebuild, like your timing.

[ex_freestyle]

when you re-built your engine you may have forgot a rag in the boot it sounds like your engine is not getting enough air or remove your choke it may help it out with the air flow i dont really know im just taking a stabe in the dark it happened to one of my buddys before

[GPracer2500]

What dariusld said. You've got to look into the throat of the carb (one way or another--you might have to remove the intake boot) and pump the throttle quickly. You should see a squirt of fuel come out of the little brass nipple towards the bottom of the throat.

Or, it can be checked with the carb off the bike as long as it is hooked up to a fuel source.

[darkzealot]

ok, ill have to check that.

oh and rebuilt was done by a mechanic, i dont think he forgot something, but who knows, if nothing else can solve the problem, maybe its the engine itself...i hope its not.

at first, i though the engine wasnt getting enough fuel when it was hesitating, then i though it was getting too much fuel cause it is an acceleration problem. But, from what ive read here, 42 pilot with 2 turns out shouldnt hurt my acceleration that much from idle with the mods i have and where i live.

Ill post after my accelerator pump check.

thx =)

[vett_09]

I have to ask this just to be sure, are you allowing the engine to warm before you're trying to run wide open throttle? The 400ex engine is tempermental when it's cold. You should always allow it to warm for a few minutes before running the engine hard.

If you are allowing it to warm, and I would imagine you are, go through and check to make sure there's nothing blocking air flow. Air is just as important as gas and if your snorkle or air filter is clogged, it could result in hesitation.

[darkzealot]

yes i let the engine warm up, let it idle in neutral for like 2 min, then ride it smootly for 3-4 mins. And i gotta clean my filter right now, but i had the bog when my filter was brand new ( i just bought it, im cleaning it for the first time today )

If that can help any, yesterday i noticed that my quad idle good, but still miss a little bit when its at operating temp.

thx for your help

[darkzealot]

i just checked my accelerator pump, its working, but part activating the pump is worn. Do you think this is the problem ?

here are some pic to help.

[darkzealot]

this shows worn lvl and normal lvl.

[honda6490]

Thats not worn, thats just a ridge to keep the throttle positioner thing in place, I just had to rejet today and saw this clearly because I accidently took the cover off the accelerator pump area instead of the jets cover.

[darkzealot]

i just went back on 42 pilot 3 1/2 turns out . i didnt remember what was the problem with that setting. Well, i have big loss of power under 1/4 throttle and the engine will just die if i pull the clutch for too long ( at operating temp ).

So this is too rich..right ? But i dont remember the engine dying like that when i pulled the clutch with the 45 pilot and 2 turns out ?! :confused:

Would that means i have to go richer on pilot but leaner on fuel screw ? ( and it is a fuel screw ? right ? just to make sure since nothing worked so far !)

Once i get on the right setting, i hope ill never have to rejet slow circuit again. NeVer !

Thx ! i still need your help ! lol
oh and btw, i put my stock CDI back on just to make sure its not a cdi issue...and its not =/

[GPracer2500]

THIS THREAD (http://www.exriders.com/vbb/showthread.php?s=&threadid=229923) might help with getting your pilot circuit sorted. Some of the pics aren't working at the moment.

And yes, it's a fuel screw. The fuel screw is essentially a fine tuning adjustment device for the pilot jet. The pilot jet, fuel screw (or air screw on two stroke carbs), and the mostly irrelevent pilot air jet (which is non-replaceable on the 400EX carb) all combine to create the pilot circuit.

What about the needle? I know you mentioned you're on the third groove. How does the the 2nd or 4th position affect the stumble?

Be aware that wacking the throttle open from idle creates conditions that carburetors have trouble dealing with. It's a fundamental deficency in the way carbs work. AP's were invented to combat the issue but they don't always get the job done. The 400EX's AP lacks the tuning features found on some other carbs which means you're mostly stuck with it as-is. In many cases a from-idle-throttle-wack will kill an engine when that's what you're trying to do. But under real world riding conditions it never comes up--in part because your brain learns which throttle inputs work and which ones don't. I'm not suggesting you should ignore the issue or "learn to ride around it"--if it's bad it should be addressed. But if it only occurs in the driveway when you're looking for it to happen and never comes up under actual riding conditions....

[darkzealot]

thx you very much for your reply ! I tried with the needle clip on fourth notch, it was oviously too rich. I will try with the second position. And i will go with 42 pilot 2 turns out on fuel screw, this pilot setting seemed to be the best so far.

thx :)