Need Help with Surging 125
 

I picked up a 125 and it starts great but when I would increase the throttle the exhaust would get super hot and glow red and the governor would continually surge on and off.

Here is what I have done so far:

• Replaced Walbro carb with Kohler carb from 127
  
• Set timing and it was way off
  
• Checked and adjusted valve tappet clearances, they were off a bit
  
• New plug gapped appropriately
  
• Adjusted high idle with no luck of fully eliminating governor surge

Since all the changes the hot glowing exhaust has gone away and the surging isn't as bad but still continues.

Any suggestions on next steps??

Thanks

The Carb is running too lean.

Lean condition is the usual culprit. Usually the carb but it can be other things, such as intake leak.

Does the surging go away when you pull the choke out a little?

Good suggestion, I forgot about the choke trick.

I'll try that when I get home tonight.

Loose and sloppy throttle shaft in the bore?
Try a dab of thick grease smeared around the shaft whereb it goes into the carb. May need a bushing.

Ok, so this is performing the opposite of what expect it to do.

The more choke I give it the rougher it runs and the more the governor kicks in.

The same happens the more throttle I give it, rougher running and the more the governor kicks in.

Starts and idles like a dream and runs worse and worse the more gas you give it.

I even tried to adjust the carb and richen it up and the rougher it runs and more the governor kicks in.

I agree with a carb condition...I know you switched carbs, but you just are not sure that the one you swapped in is working fine.......Try using a propane torch....do not light it...just aim a low jet of gas from it at the point where the carb connects....if the roughness smooths out....you have a vacuum leak

Try resetting the governor if no change, give the carb a good cleaning.

I have never reset a governor but it doesn't look to complicated.

Probably good to check that off the list.

We will see tonight how everything comes together.

Thanks

Along with all that has been suggested, I would double check the timing/points again.
Make sure you are using the "S" mark.

https://www.onlycubcadets.net/forum/showthread.php?t=14