More jetting problems. More help from you guys!

Ok, here we go again.


My kx125 2004.
it's broken and and been rejetted from stock

stock settings:
pilot- 40
clip pos-3
main jet-420
air screw-2 and half out

new settings:
pilot-37.5
clip pos-2 (from top)
main jet-410
air screw-2 and a half


so, i set the carb, banged in a new plug-
i started it up, second kick, sounded great. not as a dull a sound as it's had so far.
left it over night and took it out today.
i sarted her up and she sounded crap, it idled ok but when i revved high (almost full) it bogged and misfired.
i let it warm a little and i stucki it in first, the power just wasn't there, i got up to third and when ever i revved to just over half throttle it sounded really bad, like it was misfiring.
when i pull in the clutch and come to a halt then rev it hard it bogs really badly. the bike wasn't smoking a great deal, seemed about right to me.
but it was obvious the bike wasn't right so i killed the engine and took her home.

i took out the plug and the ceramic part was a nice tan colour (very light brown) the threads were wet and black and so was the outer edge of the plug but the ceramic part was tan brown.

so, i'm completely lost now.
all i could put it down to is my oil ratio.
i'm using fully synthetic silkolene race oil at 32:1.
when i mixed the fuel i did accidentally put in an extra 10-15 mls of oil to 3 litres of petrol.
so, i guess there was a good amount of oil in there.

so, i think i've covered everything there. the plug looked pretty good, the bike sounded and felt crap (especially in the mid to top end of the throttle) and i may been a little over-zealous with the oil.

any ideas?

Ok, cheers guys.
It definately wasn't the plug cap. i always double check that.

Like I said, the plug was in great condition, good tan colour and the first 3 or four threads of the plug were wet (which i have been told is a good sign)

what confuses me is that even though i was fouling the plugs on the factory settings the bike was quicker and didn't bog like it is now.

So, what could it be. the bike has been leaned out so surely it should be a little better than it was before, not worse.
I'm really confused on this one???

could it possibly be the abundance of oil in the fuel- 32:1 fully synthetic and could it also be down to the fact that the chamber is full of oil too and just isn't getting burnt off??
I ask that becuase the one thing I haven't sone since break in is clean out the chamber (i know thats pretty slack of me!) so could it be that. i'm also using a 9 plug- could that have anything to do with it??


I'm still confused with this one guys.

thanks again.
something did occur to me today though.
I had a look at my old plugs,, they are all obviously fouled (black) but when i looked deep inside the threads i noticed that the base of the ceramic part was a grey almost browny colour.
isn't this part of the plug the part which tells you how the main jet is running, if that is the case then wouldn't that mean that on the stock setting of 420 that the main jet was actually set up quite well for my riding and weather etc and that by me leaning it down to a 410 it has actually made the main jet too lean.
that would kind of make sense to me as the bike only began to bog on the mid to top end of the range.
should i try knocking the main jet back to a 420 and see how that goes?

Well, I figured it out and guess what...You were right, it wasn't the jetting at all.
it was the god damn floats in the carb.
it was only by chance that I noticed but when i pulled my bike up after a quick run, i killed the engine and forgot to turn off my fuel tap (i usually turn the tap off straight away) as i jumped off the bike i noticed fuel pouring out of my over flow tubes.
it hit me straight away. problems with the floats.
I stripped the carb down again and had a look. I couldn't find anything major in there and the floats themselves weren't punctured or anything but i did notice a very tiny piece of grit and grass that had lodged on the needle that the floats pivot on which i figured was stopping the floats falling and rising properly. So, i cleaned it out and so far so good, she sounds great. my plugs a good colour and i got my top end back.


cheers again people.