2 stroke topping out early

[JonathanC]

Hey guys I have the 66/80cc bikeberry engine with stock carb and expansion chamber. I’ve noticed that the engine seems to max out speed when I’m only at about 3/4 throttle and it will go about 25mph. Is this because I need to adjust the carb or is there another issue that I’m looking over. Any advice will help I’m still new in this hobby and I really respect all the feedback I get from you guys!

 

[JonathanC]

Also I don’t know if it’s related but if I’m going about 20mph and I pull the clutch the engine will start revving super high. Sometimes it’s so high I have to cut off the engine.

 

[Wrench]

Intake air leak

 

[DAMIEN1307]

You have an air leak or multiple air leaks somewhere along the line which also means your running very lean because of that air leak.

Your gonna need to troubleshoot things like if the carburetor is seated in properly to the intake tube and if that tube has loosened up at all.

Also check that the exhaust is still on tight.

The most overlooked thing to look for though that most newcomers to our little spot/hobby seem to always miss is the fact that you have to retorque the four head bolts on the top after every single heat cycle while your motor is breaking in...In many cases you might have to retorque things for the first two hundred miles or so.

This is a major cause of air leakage, running too lean, and poor performance.

Torque setting is 144 INCH pounds on a quarter inch drive torque wrench that you can buy at Harbor Freight for about 20 bucks.

It must be torqued down in an X pattern and MUST be done ONLY when fully cold or you will strip out the threads...Do not forcefully overtighten.

 

[ImpulseRocket]

Just to also say it. Definite air leak. Need to resolve that ASAP or real damage can occur to the engine.

 

[GW's Motorized]

Yup, air leak is rhe verdict.

 

[JonathanC]

You have an air leak or multiple air leaks somewhere along the line which also means your running very lean because of that air leak.

Your gonna need to troubleshoot things like if the carburetor is seated in properly to the intake tube and if that tube has loosened up at all.

Also check that the exhaust is still on tight.

The most overlooked thing to look for though that most newcomers to our little spot/hobby seem to always miss is the fact that you have to retorque the four head bolts on the top after every single heat cycle while your motor is breaking in...In many cases you might have to retorque things for the first two hundred miles or so.

This is a major cause of air leakage, running too lean, and poor performance.

Torque setting is 144 INCH pounds on a quarter inch drive torque wrench that you can buy at Harbor Freight for about 20 bucks.

It must be torqued down in an X pattern and MUST be done ONLY when fully cold or you will strip out the threads...Do not forcefully overtighten.

I have retorqued the head bolts several times. Maybe from riding it a lot the carb has backed off the seat a little I will try that first and I’ll let y’all know if it solves anything

 

[DAMIEN1307]

I have retorqued the head bolts several times. Maybe from riding it a lot the carb has backed off the seat a little I will try that first and I’ll let y’all know if it solves anything

Does your carb have the O ring installed inside it where the intake tube seats into the carb???...It needs to be there in order to make a proper seal.

 

[CENTURION]

Try a good quality bolt/nut on the carb intake, I could never get the supplied Chinese bolts to tighten enough without stripping.

 

[Whitewill1412]

Are you letting off the throttle before pulling the clutch?