I can only speculate:

Atv rolled over or turned on end or side?
Float level too high (but you would have gas from the overflow tube as well)
Backfiring through carb due to bad timing etc?

Outside of that, I don't know...

 

i bought a 1999 breeze 125 and it suffered the same exact symptoms. i bought the jets new off ebay and now it idles smooth and runs like a top. i have rebuilt and cleaned many carbs over the years and this was a breeze for my breeze.

thanks for posting this info it really helped me out.

 

I went up to 85 and 15 jets. I still have to turn out my air/fuel to 7 turns to run best! I have teflon tape on the threads to hold it in. It is still turned in 9 full revolutions from all the way out so it is secure but 7 turns is not right.

What is wrong? I have a brand new intake boot. It has an M on the side of the carb so I think it is stock mikuni. But it looks too new to be original. 2001 breeze.

I am aware this thread has been dead for 10 years. But it has the best info I have found for my issue.

 

I would be suspecting a manifold leak. Yams are notorious for them, and it is most likely to affect air fuel ratio at idle speeds. I also got a 125 Grizzly with a suspiciously new looking carb and had endless problems getting it to run right, so I suspect someone had bought a new Chinese carb and been unable to set it up, so sold the bike on. Another thing could be the float level not set right, it is adjustable on that carb. The machine I worked on was dribbling.

 

I have a new manifold but I will double check gaskets or upsize gasket thickness.

I found manifold with big rip in rubber and figured I solved it.

What are the dangers of having the fuel/air screw out 7 turns if it is running smooth. Is the 7 turns compensating for another issue and balancing things to safe conditions. Or is there a bad condition and 7 turns make it run smooth but will burn up engine, burn hot?

I'm kinda fine with it at 7 turns or was going to try stepping up to 17.5 on pilot to see if that reduces turns. My daughters bday is on Saturday and I'm debating if it's good enough or should I keep grinding for perfect running and normal carb settings.

 

About the only way to be sure the air/fuel mix is about right is to take a look at the plug after it has been used for a while. Black and sooty means rich, white and glazed, lean.

I got a Yam 250 in which had stood for a long time. took carb off and it was full of green fuel from dissolving brass. Cleaned it out and noticed the idle mixture screw was missing altogether, and from the crud on the threads, had been missing for a long time. Anyway, thought, this thing is not going to idle, but it must have been running without it to get gum on the threads, so I will see if it actually starts. Tried it and it ran fine, idled fine. You could see the inlet tract through the hole, so would have thought it would have been getting too much air, but on the "if it aint broke" principle we gave it back to the owner who was quite happy that it ran.