From my expierience from Tuning Nitro Motors ( These are the hardest to tune engines) it sounds to me like you are "loading up" a term referred to when you are to rich and drowning the plug

Ken

 

Here is what I would do. I am a certified yamaha mech and I have worked on just about everything out there. This is what I did with mine. I took and put in a 125 main and turned the air/fuel mix to 2.5+or- .15 turns. Ur best bet is to get a kuoba and do it that way if u dont have a small right angle screwdriver. Check that first and maybe pull it out and check it for debris in there cause that would make it not run and do weird things, Also check ur float bowl. with the carb off turn it upside down with the float bowl off and see where it is opening and closin. You might be starving it for fuel and no fuel is getting to the main. Also what main are u using cause I found that dg mains touch the bottom of the float bowl and if u dont cut a grove a little bigger in the jet it wont get fuel cause it touches the bottom. Check all of these and let me know. U can pm me if need be.

 

who's running dg main jets around here? I've never even heard them mentioned here. It's either oem keihin, dynojet/moose/fmf. He's too rich, 'nuff said. Too much gas, not enough air to burn it unless he's riding it thus why it was running well most of the day. Off idle it starts and that's when he's either not riding or just starting out.

 

what are DG jets?

 

Thanks again guys... i took the carb off last night and trying to fiqure out what i want to do with it as far as jetting goes.. but i guess i wont be able to do anything untill next week. my girlfriends parents are here. booo

the plug does look a little funny when i have had the problem the insulator looks half black and half tan. but after it seems to run ok. it looks ok again.

as i said before i was thinking to change:

put stock pilot back in (from 40)
128 main (from 132)
clip 3rd (from 4 from top)
klx snorkle
keep kouba 2.5 turns

you think thats horrible?

 

the settings you are going to, is how my bike is set up.... do you have an exhaust? just take the snorkel out.... leave the airbox lid on...... thats howmine is..... my klx and kdx snorkel are in a box in the garage. good luck, this is where you get good at removing the carb... lol

 

My 1979 KE250 is doing the exact same thing that your bike is doing, im trying to figure it out myself, i'll let you know what i did if i fix mine. I would like to know what you did also if you fix yours

 

Last week I went for a 100 fire road/ trail ride. One block from home I dumped it and the bike was laying upside down. Nothing hurt but my pride, took her home washed and filled the tank. Next day very hard to start, then it died

Fuel filter was full, had spark, pulled apart on off switch thinking water, changed spark plug. Nothing!!!!! Then I pulled the fuel line- Nothing!!!! full tank of gas, line was off before the filter???? Then I removed the gas cap flow city

I had put on one of those vent line check valves, and after I dumpped the bike it must have stuck closed.

Some times its the simple stuff.

 

HI,

Just an update for any of those having the same problem...

so i rejetted.

during the rejet. i cleaned the rubber tip attached to the float there seem to be a white residue on it ( i wonder if that was sticking and letting just enough fuel in to start the bike). Also when i rejetted i didnt read the instructions carefully and i only put one of the fmf jet kit washers on the clip and it specified two.

128 main
3rd clip
2 1/2 turns
kdx snorkle
stock pilot

test ride:
ran ok
poor idle
plug insulator was white indicating a lean mixture

then i chaned the 128 to 132
test ride:
ran ok
poor idle
plug insulator was white indicating a lean mixture

then i decide to go back to my orginal set up because the plug looked a little better:

132 main
4th clip
2 1/2 turns
kdx snorkle
40 pilot

while doing this i noticed the that the stock slide needle had a little more clearence in the diaphragm hole and that the fmf needle seem to be a little tighter so i opened that hole up justt a tad for some more clearence.

havent taken it for a test ride yet or pulled the plug but the idle seems to back to normal and isnt studdering.

will update

 

I am having the same exact problems you are and I have everything identical but the 40 pilot. It will run like a rocket for a while, then stumble and when you give it gas it will die. It will idle fine, but blip the throttle and it dies. I think it's this damn needle. I'll go in there to make sure it's straight up vertical and not in there at an angle. I swapped it from the 4th notch to the 3rd and I don't know if it dropped in the hole straight or got hung up before it went into the bottom hole in the carb. I am also going from the 132 to a 128 and putting my airbox lid back on that I did a 3x3 mod hole on. If that doesn't fix it, I am taking the dj kit out and putting the keihin N1TC and a 128 keihin mj in. This is probably what I should've done in the first place. I'm trying to get a hold of kouba to try and get a t-screw but they don't seem to want to sell me their t-screw, they want me to order something else too. Are there any alternatives to kouba as far as getting an adjutable fuel screw? they're kind of pissing me off with their minimum order crap.