Keeps fouling spark plugs with lean jetting???

[400man]

my 400 has a problem of fouling the spark plug fairly often. the motor is stock (2000 model) with fresh rings and hone, valve seals and gaskets, ect., stock carb with uni foam filter and no lid, and an old style big gun full exhaust system. I just got through putting on my new clarke 5 gallon tank and new hand guards and went to go for a quick test ride and the thing wont hit a lick. I pull the spark plug and its dark black and a little wet from cranking on it for a few minutes.

the current jetting is:
needle clip -- 3rd from top
A/F screw --3 turns out
pilot -- 38
main-- 152

from all the reading ive done on here I should be very close to the right jetting with the mods I got. and one other problem its got is when you first start it up for the day, and cuts out and pops and back fires real bad from 1/8th throttle to full throttle, acts the same no matter what. it does this untill you ride it for a few minutes and get it to normal operating temps and then the poping and missing and back fireing stops and the bike runs good from then on.

[honda400ex2003]

to get it to stop popping a bit you can do two things, depending on if it is really bad or not. 1st you can try to go out to 3.5 turns out on the f/a if it is not too bad and see if it helps. otherwise you can put in a 42 pilot and that should clear it up. as for the plugs you sound like you are jetted really close to what you should be. i guess you could try to turn out the f/a and see if it helps but that will richen it up a very little bit. you could try to go to the 2nd clip position and see how that helps too. have you done any plug chops to see if your jetting is good up top then at different points? you can test any circuit with a plug chop also. just a few suggestions for you to try and see if they help. good luck. steve

[400man]

well I guess the pilot was my problem ;) . I put a 42 in it and at a cold start up it doesnt act near as bad with the back fireing and cutting out. it might pop or studder one or two times but thats it.

but about the fouling plugs deal, do you think a hotter coil would help me out? ive been reading about the AMR coil and it sounds like it would work perfect to fix my problem.

[tri5ron]

might want to check/verify your flywheel position and torque.
is it possible that it might be loose, or possibly a sheared key?
just a thought from "shooting in the dark".

[speedfreek]

How does the spark look? A weak spark could be coming from your stator or coil going bad.

[400man]

well im having trouble with fouling plugs again. mods are big gun full exhaust and uni filter and SRP +6 degree key, and today I just installed my amr coil and comparing the spark between it and the stock coil tells me something else is making it have a weak spark. could it be the stator?

[storms400ex]

sound like you need to richen it up too full exhaust and no lid you need more then a 152 main

[speedfreek]

Originally posted by speedfreek
How does the spark look? A weak spark could be coming from your stator or coil going bad. Exactly what I was thinking.

lol. I just quoted myself! lol

Like I said earlier. Look at your spark and compare it to someone elses bike.

[riggsracin]

make sure you choke is open all they way and stays open when riding

[tri5ron]

Originally posted by riggsracin
make sure you choke is closed all they way and stays closed when riding don't you mean "Open" all the way ???

[riggsracin]

thats what i said lol

[tri5ron]

Originally posted by riggsracin
thats what i said lol Yeah right,...
Try again,

but editing your post, after you are quoted, dosen't work in your favor. :huh

[riggsracin]

lol, nice try oh

[400man]

well, heres the best way I can describe the spark (with the gap set at .28) when I ground a spark plug againts the side of the motor and hit the starter button, the spark is very very small and eratic and jumping all around the electrode tip, and this is with a brand new plug.

and as far as jetting, it could be worse then it used to be since its like 15-20 degrees with snow on the ground. the current jetting is 152 main, 42 pilot, and needle clip in the middle slot. when its cold it back fires alot through the carb when I hold it like 1/8th throttle, and backfires out the pipe when I puch it past half throttle. but now after about 5 or 10 mins of riding around getting it warmed up, it all clears up and runs awesome with no pop or backfire at all.

[riggsracin]

What color is the spark red or blue

[400man]

Originally posted by riggsracin
What color is the spark red or blue

its so small its hard to tell. i'd say its more of a white/blue spark.

[riggsracin]

blue is got and hot spark if its red its not strong enough

[400man]

well just when I think my problem is solved, it does the same old crap. Im averaging about 1 good 2-3 hr ride before my bike fouls the plug out and wont start the next day that I want to ride. and whats funny is that its been pretty cold here, been below freezing mostly, and should have helped leaned out my jetting. same jetting as what I posted on the first post here. the thing will pop and back fire, if it does happen to start, so bad that its embarasing to be seen on :ermm: but clears up after about 5 mins of riding. and it does this in all throttle positions when its cold.

[JOHNDOE83]

when the motors cold take your filter and air box lid off start it and ride it and see if it still backfires or pops? if it clears it up you might be to rich....

[riggsracin]

you could have weak fire

[togup]

the plug wire assembly has a built in resistor you can actually take it apart by unscrewing it if memory serves me. I do not know why its there but I got rid of mine actually I threw it away and built a new one from a MSD 8mm wire and boot and some shrink wrap,its got plenty of heat now! I have been running that set up for a couple of years ill post a picture tomorrow

[400man]

yea please post some pics, i'd be very interested. I have a AMR coil on it right now, and when I compared it to the stock coil, the AMR coil made barely a stonger more noticable spark.

[togup]

the factory cable unscrews from the coil ,I found some shrink tubing that fit on a new sparkplug wire cut to the right length carefully screwed it on to the coil screw then slipped the heat shrink on for added protection against water and pulling off heated it up and voila your done

[togup]

bump

[dobber21]

i dont know if anybody said anything about fuel but are u running regular or premium fuel? i used to run mine on regular and fouled plugs really often in the winter, then i started running premium and i didnt have to touch my plug once during the winter i went through like 5 plugs one winter on regular. Its just a thought and dont know if anybody thought about it, figured i would throw it out there.

[400man]

yea im running premium in it