i am having a real time of it trying to get my rig running right. i had it to the shop in feb. after another shop put in a new needle and seat. it ran bad before and after the the n&s was installed. the 2nd shop i took it to said there was a nozzle that was dirty so they cleaned it out and the atv ran like a top. after a few monthes the bike started doing the same thing. runs rich, black smoke and loads up. plug is covered with black. this is what i did so far: took carb apart cleaned out everything including pilot jet hole (with wire), main jet, air mixture valve, lowered needle valve one notch, checked float and air hosed every hole and crevice in the carb. air vent hoses are not plugged. new plug, new air filter, no air leaks that i can find. bike starts up and idles ok, but when i throttle it loads up. when i turn the idle adjustment screw in the bike will die. i can leave the screw about halfway and bike will idle. until i moved the needle valve you could turn the screw in or out and the idle would not change up or down. the choke seems to be working okay but the bike just loads up and runs rich. taking the air box lid off does not make bike run much better. bike has new gas and still no change. the only thing i found in the carb that i was not quite sure about was the position of the o-ring that goes on the air adjustment screw. the o-ring was positioned down in the hole with the spring. it was tilted and i had a time getting it out. what is the correct installation for these three items. air adjusment screw o-ring and spring? thanks a bunch for any help folks. D.T.

 

carb depiction
#29 is the mixture screw assembly.

Removing the air box lid, should make a bunch of difference. Is the choke staying on?
It runs better when cold, and then gets crappier as it warms up? This points to a rich mixture.
If you turn the valve on the gas tank to off...while running, eventually before it runs out of gas....does it clear up? If it does the float may be set too high, and that makes for rich mixtures.

 

thanks for info. the motor does speed up and smooth out when i turn off the gas. i have checked the float and set it but that has not helped. in the picture of the air adjustment screw it looks like there are 4 items. i have the the screw the spring and the o-ring. is there another item in the pic that i may be missing? it is hard to see the pic clearly. thanks D.T.

 

It is hard to see, even the parts catalog at the yamaha motors website is hard to see.
I know theres at least one o ring, and the other thing might be a second o ring. Does the motor idle quality change as the mixture screw is adjusted? If it does change , then id assume the mixture screw is put together correctly. Sometimes that inner oring doesnt come out with the screw, it stays in the carb,
Turning off the gas, and haveing it run better...sure points to the float level.
Have you put the needle back to the middle clip position? I know it wont effect idle mixture, but if its worn, and high, it may leak gas while at closed throttle.

 

In my manual it shows pilot screw,spring and what looks like [2] two O rings,on carb models with choke lever,looks the same on the other model One O ring could be a washer I can't tell from the pic. I was just helping a guy on the suzuki board and his rich problem was too much oil on the filter.

 

okay guys i will take the top off and raise the needle. that may help. i had the carb off again today and i can not see any problem with dirt or adjustments. the bike did have a bad problem leeking gas before the n&s was installed. it would leak into the crankcase and airbox. ouch! i don't think there is too much oil on the filter because there is not much change in the way the bike runs even with the air box lid off. i appreciate all the info. D.T.

 

my son's lt160 was leaking gas the same way amd it was the float,one bowl fell off and the gas flowed right through.