need desparate help with briggs 3.5 engine

[alexkarter]

ok, the engine starts. i start it with choke on, gradually move it to open/run and its idles ok. back fires sometimes. sometimes puffs of black smoke from the exhaust. here's the problem, , when i rev it/ open the throttle, it only works if i do it slowly. if u push the pedal fast it sputters and dies. also it only runs at half/low throttle, when u rev it all the way it dies. i dont know if the carb is adjustable. there seems to be a mixture srew but it makes no difference. the gas cap is ok, tank is new.

it has spark, clean gas. the engine is only months old! i dont know what is wrong.

 

[brendonv]

The mixture screw should be 2 1/2 turns out. Maybe your jets are dirty.

 

[Blazkowiez]

If you've cleaned the carb and replaced the diaphragm gasket, occasionally the spring in there gets compressed strangely, you can reposition it fairly easily, but when the spring is compressed like that you may have problems similar to what you've mentioned. I do agree you also must check your air/fuel mixture.

 

[HellSpawn]

Lots of black smoke like that on a 4 stroke generally means its running a bit rich, The fact that it kills out with you quickly snap the throttle open also tells me the same thing. bit rich.

 

[solomon]

I agree, sounds rich.Do a plug chop and check. To adjust it start the motor and while running turn the screw in slowly and try revving the engine until it runs fairly good, turn the opposite to richen it, although it does sound as if it is currently too rich. Let it idle for at least 10 minutes and then do a plug chop to determine what to do next..

 

[alexkarter]

k guys thanks for the help ill update on fri