Really stumped

[Shadow57x]

Ok.... I've been building stand up gas scooters for years and just got done building my 2nd 80cc bike. 1st one I did ran great but this one has me completely stumped. Runs great intil I let out the clutch. Re built the motor new carb new cdi box spark plug muffler etc. Finally I just broke down and bought a new motor and still the same thing. I work on 2 strokes for a living and I'm aware that vacuum leaks have a big effect on engine proformance. No leaks and chains not binding when peddling just dies under load. Is it possible that I got two junk motors in a row? The motor will not run with the choke on of half on.

 

[weefek]

More information please..

What engine kit?

What exactly do you mean by vacuum leaks? That's more a 4 stroke automotive engine thing.

What spark plug are you using?

What carb are you using?

What does Choke on of half on exactly mean?

This is the dumbest question of all but are you letting the clutch out from a dead stop? These types of MBs require a bit of speed before you engage the clutch. Just trying to cover all the bases.

 

[Shadow57x]

It's a 80cc 2 stroke kit. I'm using the standard carburetor that comes with it. Vacuum leak means a air leak. And I'm peddling while releasing the clutch while I throttle up. When I release the clutch it shakes and then dies. When I do get it going, it only wants to run with the throttle slightly open and peters out at half throttle and full throttle.

 

[weefek]

If it's a new engine , still during break in, it may take awhile to get going. Let it limp along at near idle until it gets warm.

 

[Chainlube]

Check your float, if it's too high, there will be too much fuel and it will bog and not run. If it's too low, it won't get enough fuel and run some but peter out. The float could be sinking, but I don't know if you used two different carbs or switched the one from engine to engine.

 

[Shadow57x]

Ok I adjusted the needle and tightened the head and still ran crappy intill I rode it for a mile then slowly started to straighten it self out. Now it's running decent but still feels like it's a little fuel starved.

 

[Chainlube]

Ok I adjusted the needle and tightened the head and still ran crappy intill I rode it for a mile then slowly started to straighten it self out. Now it's running decent but still feels like it's a little fuel starved.

Move the clip on the metering needle down one notch.

 

[gary55]

Ok I adjusted the needle and tightened the head and still ran crappy intill I rode it for a mile then slowly started to straighten it self out. Now it's running decent but still feels like it's a little fuel starved.

When you rode it for the mile was it initially showing excessive smoke and maybe spitting some raw fuel from the exhaust prior to it coming around?