I do not know much about this stuff but I would like to know what can cause a 50cc atv to rev up and down at high speed. It seems like at anything past a little under 3/4 and I hear a revving sound in short bursts. Is this redlining, or ???? All I can tell you is that the carb does leak gas, the bike is still new. The bike otherwise is fine. It fires up on the first try nine times out of ten (unless it is cold out) and never stalls. If you could give me a few ideas of what it could be so I can understand what is happening. Thanks

 

where is the carb leaking from. Maybe the float bowl is emptying faster than the needed amount of fuel by the carb, you need a steady amount of fuel in the float bowl.

 

The carb is leaking from the fuel line to the engine. The leak is slow. Maybe one drop every 5 seconds. Not that i would know but I doubt it is because of the leak, but i am thinking a couple of things. If the float is stuck maybe, depending on the position it is stuck, maybe the carb isn't able to get enough fuel in it to run that fast, or maybe the main jet ( i think that is the one that is for more than half throttle) could be clogged. I read on this website that chinese put gel packs that can tend to clog or make the float stick. Does this make any sense????

if the bike was redlining would it make the bike rev up and down quickly???

 

If it was tapping the rev limiter it would almost act like a miss or cutting out but it sure could be the rev box. Vindell is correct to make sure that you have enough fuel in the bowl to supply the motor at that RPM. You may want to check the petcock as well to make sure there is good flow.

 

the flow seems good to me. when i take the hose off the carb there is a steady flow of fuel coming out. i agree that the fuel doesn't seem to be enough at the higher rpm but do not know why. what can i do to increase the flow of fuel???

 

How does the plug look, you may need to jet up a little. Just a thought that maybe you need a little bigger jet in it?! You could also check the venturie to make sure it is working properly and the float is fnctioning correctly.

 

Sounds like it could be sucking air.
Spray carb cleaner around the intake to check for air leaks.
If not there, spray around the stator and the back of the front clutch to see if the main seal are leaking.

 

You say your fuel line is leaking before the carb. I would think that under higher rpm's the motor could suck air into the fuel line and might cause problems like that. also could be what was also stated as being an incorrect float bowl adjustment. Was their anything done to engine like big bore,high flow air filter etc. than from stock?

 

I'm with hotblooded..Sounds like it could be a rev limiter..

 

bike is 100% stock. The leak is on the way out of the carb by the way. How do you disable the rev limiter, or is it best to leave it? I have heard about cutting pink wires but not sure how universal that color coding is.