Bike speeds up when out of gas

[Ajh413]

I've had my bike for a few weeks now bought it already broken in and in great shape is a 80 cc China girl engine. It used to be faster and run clean now all of a sudden the muffler sounds like it is sputtering when riding and it is alot slower. Just about when I am about to run out of gas all of a sudden it goes back to normal and speeds up quickly for a few seconds then does because it is out of gas. Was wondering wht could possibly be the problem

 

[YetiWoodz]

9 times out of 10, everytime I have a problem relating to power loss or difficulty starting, the spark plug is fouled and/or the cylinder head is loose. So I'd check that first.

 

[GreasyChris]

The engine speeding up when you run out of gas is because ther fuel mixture goes extra lean just before you run out of gas. The sputtering is most likely the cylinder head coming loose. They need retightening periodically. Make sure your exhaust isn't loose either and check for air leaks

 

[darwin]

WOW, if bike speeds up after running out of gas I need to quit putting gas into the tank! Zoom zoom.

 

[Chainlube]

If it's getting slower as of late, pull the carb and clean it out. Does it have a fuel filter on it?

 

[Ajh413]

Pulling the carb and air filter helped it quite alot also their is a bolt on top of the exhaust that I tightened that actually made a world of difference it's almost back to how it used to be. Next time I run out I will try to run it leaner and see if that fixes it fully.

 

[Greg58]

Pulling the carb and air filter helped it quite alot also their is a bolt on top of the exhaust that I tightened that actually made a world of difference it's almost back to how it used to be. Next time I run out I will try to run it leaner and see if that fixes it fully.

The leaning out Chris is talking about has nothing to do with gas to oil ratio, it's fuel to air ratio. Almost all I've built have improved with jetting, you'll learn a lot over time. Use a torque wrench to tighten the head nuts, 12-14 ft lbs is all it needs. You can warp the head if you tighten it unevenly.