Reply To: Hello from Germany, work on it til it runs – GV125M E3 2007 Carby
Mikuni vacuum fuel pumps can be disassembled, cleaned and assembled. Most likely you will find some dirt inside. Nevertheless if the bike runs “okish” but sometimes fails to start on the first crank and holding open throttle over a long period of time triggers a progresive loss of power, you might try to add some clenaer to the fuel. It will most likely improve it to some degree, it might take a looooong time and many refuels and most likely it will never reach 100%. Otherwise you’ll have to do what M77 suggests you, carburetor cleaning off the bike and adjust them when reinstalling.