Small Engine cuts out with throttle.

[colinrmitchell]

Hey, everyone.

I got a small-engine problem. I have a B&S 18HP twin-cylinder. It's got a new ignition, and I recently cleaned up the carburetor.

My question is, after it runs for 10-15 minutes (gets to operating temp), it starts to die when you give any throttle past idle. It idles great and starts at idle real quickly. I am sure that it is a lean/rich problem, as I have messed around with the jet screw on the carb without thinking about it.

Is it running rich? Lean? How should I go about messing with the mixture screw as a starting point?

Thanks for your help.

 

[BlackBII]

After it dies, pull the plugs and check 'em out. Black is rich, white is lean, also, if it's running rich, it'd probably blow black smoke.

If I remember right, those motors' air mixture screws were 1-1/2 turns out, and then you adjust from there.

I'm guessing lean.

 

[LearjetMinako]

The fuel mixture can be too both ways, too lean or too rich, and the engine will stall. A good starting is to get the engine to idle first (which is done). Find your high speed mixture (if there is one, there may be only 1 fuel mixture screw) and turn it clockwise till is seats. Do not tighten it down, only till it just stops turning. Then turn it counterclockwise 1 turn and try again. If the engine is able to get up to running speed, richen the mixture till the engine rpms just drop slightly. Then give it about a 1/4 turn leaner.

For 1 screw carbs. Basicly you set the mixture screw for the running speed and the idle stop screw for the idle rpms.

 

[Will]

It's going lean. Jam the choke on and see if it keep running. Needs a kit in the carb or the fuel pump investigated.