Bet & Win 125 losing power after pull away

[Marike]

When I pull away at a robot or stop street my Bet & Win 125 pull's away more or less normal but then loose it's power and slowly accellerate to max speed. I'm so frustrated and try not to slow down or stop anymore!!! We checked and cleaned the carborator, checked the drive belt, changed the oil and we still have to clean the oil filter. Please let me know if this sounds fimiliar!!! What can it be???

[zombie]

Hi Markie. Welcome to the forum.

There are lots of potential causes.
Off the top of my head... A worn out control spring on the rear pulleys will cause a sudden load, reducing acceleration. Low tire pressure, dirty air filter, worn belt (did you measure across the top width?) I believe 15mm is the minimum width, clogged or dirty air filter, worn spark plug, mis- adjusted valves, ect.
Stick around for more input from others but that's the short list of what I would look at.

[mrbios]

Could be other things but I suspect a fuel delivery is lean so check:
  Spark plug color - if you see a white tip = lean mixture.

If the mix is lean look for:
  vacuum leaks - missing or cracked or broken hose etc.  Check the diaphragm on the carb for leaks by pushing the slide up and down.  Often when people clean carbs they damage (bend) or loose parts like a jet needle spacer or shim etc.

If you suspect the carb you can buy and after market carb for $30 to $50 and possibly get rid of all of your performance problems. 

Review these videos but consider replacing the carb:

Carburetor Cleaning & Theory three part series: