Engine stumble off idle and need some human help. ChatGPT is leading me astray !

[Darren S]

exactly what I did with the O360 in my RV4

Thanks for the response. From my testing today, it took more than "slightly lean" to get the stumble to be reduced. I aggressively leaned to the point of engine roughness then enrichened slightly. This reduced the stumble quite a bit but it was still there.

 

[ve0kog]

1. The main jet is wrong. Causes the engine to be too rich at full throttle and idle ... hence the reason I lean out before takeoff because if I don't it's blubbering rich

this is probably by design though to help cool cylinders and prevent detonation at full power. do you have a way to measure fuel flow at take off? it should be in the specified range for the engine. our lycomings are liquid cooled at low airspeed.. despite what they say

 

[Finley Atherton]

You can see the carb fuel level if you screw a fitting with clear plastic tube into the drain hole and route it vertically up. AI says it should be just below the mating/parting surface of the bowl and casting.

 

[Darren S]

You can see the carb fuel level if you screw a fitting with clear plastic tube into the drain hole and route it vertically up. AI says it should be just below the mating/parting surface of the bowl and casting.

Ahhh. Good idea. Easy way to check. Thanks

 

[Darren S]

this is probably by design though to help cool cylinders and prevent detonation at full power. do you have a way to measure fuel flow at take off? it should be in the specified range for the engine. our lycomings are liquid cooled at low airspeed.. despite what they say

So you think the float level might need adjusting?