I know i know i know, this has been asked on many forums, and here mostly cuz when i search google this site keeps poppin up, but i can't find my answer..

so, i got a 02 400ex with a K&N, spark arrensor gone and i just put a 155 main, 40 slow, and dropped the needle 1 clip and iam out about 2 1/2 turns on the air screw. so it idles excellent but when i go to give it gas it bogs down unless i ease into the throttle then it revs right up.. i haven't had a chance to drive it yet due to rain..
what causes the bog? i tryed it before i dropped the needle and same thing. i ride no more then 2000 meters

thanks guys
VJ

 

anyone help me??? i even put the 38 slow back in and i think its worst/.

 

This is my opinion from fumbling with my jetting...
And if I am wrong it won't cost you much...

In my opinion, here are a few things to look at... but the carb will have to come completely off...

#1
This carb is equipped with an accellerator pump for throttle stabs. So with the carb off, point the engine side away from you and turn the throttle linkage fast... and look for the squirt of fuel. Is it there... and does it make it straight out without hitting anything?

#2
While fooling with the above, check to make sure that your throttle butterfly and slide are synchronized... moving at the same time? If not let me know and I will tell you how to fix it.

#3
I personally think you are WAY FAT on the main jet. Look at your plug, I bet it is wet and/or black (rich). Put the stock 148 back in and see what happens. If it's lean, pick up a 150 main and a 152 main.... and make sure they are the long hex jets like the stocker... carb mfg jets are the best choice...

 

ok, the pump squirts no problem... and everything works as it should...
but i added a k&n filter #40 slow and 155main and took out the spark arensor but put the big screen on the tip, so it has a 2"+ opening and drilled 4 1" holes in the box.

I would think that if i put the 148 back in won't that mean its too lean? i thought these were lean from the factory? won't doing what i have done make it even leaner?

 

If you are skeerd... step down to a 152 and run it... then a 150...

I am pretty certain a 155 is too rich.... look at your plug.

If you want to be patient I will tell you for sure as I am going to put the 40/155 combo in mine and run it... same filter, full Yoshimura exhaust, no sparky, at 1200 ft, with the lid on and off.

 

ya if you don't mind.. just write me back on here... only u have a pipe on so that probley makes a huge difference...

 

No I have more mods than you...

Same K&N as you + full exhaust + plus I can try it with no lid at all.

I will post results... and I am thinking it will be too rich for what I have.
Pretty sure you are too fat on the main.

 

ok, so i rode for a few hrs today and heres what my plug looks like, i have the 148 main 40 slow and the needle moved down 1 notch, k&n lid on no holes, and sparky out.



does this look ok?



hard to take a good pic.


and my bike.

 

It's hard to tell... because it the one pic the porceilan looks bone white and on the other one it looks brown which is good.

The base ring at the bottom of the threads looks rich.

Mine looks the same in mine... I can make the porceilan white and the base ring still looks rich. I am not sure if it is fuel quality or what... But as long as it does not expand the carbon and dry foul my plug I am OK with it.


The most important thing to consider right now is... how does it RUN?

Any improvement?
Any popping/cracking/backfiring?
Seem to be running any hotter?

 

seems better, doesn't backfire at all as thats what i was really listening for, takes every bit of gas i give it don't bog at all, kinda seems low on the low range of the throttle tho but that could be the needle position, as i stated before its lowered 1 notch. never noticed it running any hotter, i'd like to check that with a temp gun but.. don't have one.