NEED HELP 80cc bicycle build won't accelerate when pulling throttle

[Emathews100]

Me and my uncle recently put an 80cc bicycle motor kit on my mountain bike.

It ran for a few miles at first before I had to change the tire. Nothing seemed wrong with the engine.
Now when I pedal,engage the clutch,and pull throttle I'll get zero acceleration like I did the first time breaking it in.

Could it be a spark plug issue or do I need another engine?

 

[ImpulseRocket]

Me and my uncle recently put an 80cc bicycle motor kit on my mountain bike.

It ran for a few miles at first before I had to change the tire. Nothing seemed wrong with the engine.
Now when I pedal,engage the clutch,and pull throttle I'll get zero acceleration like I did the first time breaking it in.

Could it be a spark plug issue or do I need another engine?

Commonly overlooked aspect of breaking in these engines is the need to check and re-torque the fasteners on them. In particular the head and cylinder nuts, 144inch pounds, and the intake and exhaust bolts.

 

[Amwicr]

Me and my uncle recently put an 80cc bicycle motor kit on my
mountain bike.

It ran for a few miles at first before I had to change the tire. Nothing seemed wrong with the engine.
Now when I pedal,engage the clutch,and pull throttle I'll get zero acceleration like I did the first time breaking it in.

Could it be a spark plug issue or do I need another engine

Could be a number of things, but you might check if the spark plug is fouled.

And then while it's out, replace it with an NGK-BR6HS gapped to .025"

 

[Emathews100]

Could be a number of things, but you might check if the spark plug is fouled.

And then while it's out, replace it with an NGK-BR

What other things could it be besides the spark plug. Are the China made ones just generally bad

 

[Emathews100]

I actually changed one spark plug for a cleaner one because the first one I used was blackened at the tip. I'm wondering if it's a fuel combination issue

 

[Emathews100]

I also replaced the throttle and carburetor. The pin slides just fine. The handle snaps back and forth like it's supposed to.

 

[Amwicr]

What other things could it be besides the spark plug. Are the China made ones just generally bad

Yes, they are. Also, if you are running too rich, it will foul, and won't work good. I learned this by experiencing it. It may also be harder to start.

 

[Amwicr]

I also replaced the throttle and carburetor. The pin slides just fine. The handle snaps back and forth like it's supposed to.

What carb did you put on it?

 

[Amwicr]

Me and my uncle recently put an 80cc bicycle motor kit on my
mountain bike.

It ran for a few miles at first before I had to change the tire. Nothing seemed wrong with the engine.
Now when I pedal,engage the clutch,and pull throttle I'll get zero acceleration like I did the first time breaking it in.

Could it be a spark plug issue or do I need another engine

Pro tip: turn the choke off.

 

[Amwicr]

I actually changed one spark plug for a cleaner one because the first one I used was blackened at the tip. I'm wondering if it's a fuel combination issue

Show us the plug tip