Genuine Buddy 125 Running Issues--Please Help

[CynicalCinnamonRoll]

Ok, so I have a 2008 Genuine Buddy 125 scooter. It has been having a myriad of issues for a few months now. I've managed to repair most of them myself but now I'm stumped on what to do for this one.

Repairs done up to this point:
-Fuel line and filter replaced
-Air filter replaced
-Gear and engine oil replaced respectively
-Transmission parts cleaned, rollers replaced
-Stator plate replaced
-Carburetor cleaned twice

I recently replaced the stator plate as I had been having issues with the scooter suddenly cutting out and making popping noises. It had diminishing returns the more it ran. My research indicated that a faulty stator might be to blame and so I replaced it. After testing the scooter, it didn't experience the same issue of running continuously, but new issues came into being.

Now the scooter only runs normally at full throttle. If it is at half throttle, it struggles to run fully/smoothly. It sounds/feels like it's struggling to process fuel or air. At low speeds, the scooter threatens to cut out entirely. The scooter won't idle at all.

My first impression is that this is a carb issue, but I've cleaned the carb less than a month ago. A mechanic messed up the diaphragm and got some of the jets dirty, but after I finished with it the scooter ran perfectly. I'm unsure if that would suddenly be the issue again. I'm reasonably sure that this is a fuel issue but I have no idea what to replace/clean/check.

Have any of you experienced this issue? What do you guys think the problem is?

[scootERIK]

My first impression is that this is a carb issue, but I've cleaned the carb less than a month ago. A mechanic messed up the diaphragm and got some of the jets dirty, but after I finished with it the scooter ran perfectly. I'm unsure if that would suddenly be the issue again.

I would start with another carb cleaning. Really get in there and make sure it's clean and see what happens. You could also make sure the air/fuel screw is set correctly, I believe the stock setting is 2.5 turns out but not 100% sure if that is right.


Buddy 125 carb cleaning video-
https://www.youtube.com/watch?v=CD-nPIajHAQ&t

[tenders]

What you’re describing could be a spark problem - the engine has enough momentum at high RPMs to carry through a few missed sparks, but stumbles at low RPMs. How is the spark plug, plug wire (both ends), and connection to the coil?

The temperature variability also suggests a possible valve adjustment might be in order.

I agree with your carb suspicions too, but would not mess with the air/fuel adjustment screw. That only affects idle and very low speed operation, and gets misadjusted so often that some carburetor manufacturers make it exceedingly difficult to find or adjust. Diaphragm problems in my experience manifest themselves oppositely to what you’re experiencing - low speed OK, high speed struggling.

At some point in the troubleshooting journey, there are worse things than having an extra carb in reserve if you were to bolt on a brand new one and completely rule a carb problem in or out.

Is the fuel fresh and unadulterated?