Why does my bike sputter

[theguy2024]

66cc kit with NT carb everything is checked for air leaks there shouldn’t be any unless i’m somehow missing something.

My question is why does my bike sputter like **** when I let off the throttle?

it has great power and all that but no matter what speed, if I let off the throttle it starts to sputter like it’s choking to death or like i’m going 1km/hr in first gear in a manual car..

what’s up with this?

 

[Sidewinder Jerry]

66cc kit with NT carb everything is checked for air leaks there shouldn’t be any unless i’m somehow missing something.

My question is why does my bike sputter like **** when I let off the throttle?

it has great power and all that but no matter what speed, if I let off the throttle it starts to sputter like it’s choking to death or like i’m going 1km/hr in first gear in a manual car..

what’s up with this?

How did you check for air leaks?

 

[theguy2024]

How did you check for air leaks?

I sort of just tightened the intake and exhaust and made sure the gasket were good and everything was tight.

 

[wrench]

Maybe the choke lever is moving?
NT carb choke lever
UP - Closed
Down - Open

 

[Sidewinder Jerry]

I sort of just tightened the intake and exhaust and made sure the gasket were good and everything was tight.

There's 2 ways to test for air leaks.

1) Spray some soap water mist around conection points before starting the engine. Start the engine and then look for bubbles.

2) Lightly blow smoke around connection points and look for rapid movement in the smoke while the engine is running. If there's no leaks the smoke should just linger.

 

[Mossy]

I suspect that the surface of the cylinder and intake aren't flat.. most aren't... You can use a flat file wide enough to cover most of it or something flat wrapped in sand paper... Just take off the high spots and that's every surface with a gasket... Soak the gasket in oil and don't over tighten it 1/4 turn past snug

 

[Venice Motor Bikes]

66cc kit with NT carb everything is checked for air leaks there shouldn’t be any unless i’m somehow missing something.

My question is why does my bike sputter like **** when I let off the throttle?

it has great power and all that but no matter what speed, if I let off the throttle it starts to sputter like it’s choking to death or like i’m going 1km/hr in first gear in a manual car..

what’s up with this?

Does the engine idle nice & smooth at a low RPM?

 

[Greg58]

Is it sputtering or porpoising ? I’ve had a couple of higher compression engines that would sort of gallop when I let off the throttle. I never did find a cure, lower compression engines don’t do it as bad.

 

[theguy2024]

Is it sputtering or porpoising ? I’ve had a couple of higher compression engines that would sort of gallop when I let off the throttle. I never did find a cure, lower compression engines don’t do it as bad.

it’s interesting you bring up compression because I do have my squish gap set extremely tight I think it’s at .3-.4mm when I measured a piece of solder. and yes galloping is the perfect term, it does that exactly when I let off the throttle like i’m bouncing almost and everybody can hear it lol. I guess I just have to live with it. I find that when I begin to let off throttle if i’m coasting I immediately pull the clutch a little and it’s smooth.