582 Decrease in RPM after take off

The first thing I would suggest is to remove the exhaust manifold and inspect the piston/cylinders. 

It sound like a marginal fuel starvation issue.

The carbs are not refilling as fast as need be and slowly run out of gas.

The engine slows to match the available fuel and runs at the lower speed.

If he were to reduce the throttle to a cruise setting for 30 seconds, the climb should return at least for 10 seconds or more.

You might have some crud in the carb fuel fitting or passage just before the Float Valve.

If a two stroke suffers restricted fuel supply while under full power it will most likely show some damage. I wouldn't suggest flying it until it has been inspected. If the plane is equipped with EGT guages there should have been a spike in the temps. 

Dennis Richardson wrote:

The first thing I would suggest is to remove the exhaust manifold and inspect the piston/cylinders. 

Hi Dennis

Thank you for the reply

I did this when I removed the manifold and checked the muffler, they look good

Bill Hertzel wrote:

It sound like a marginal fuel starvation issue.

The carbs are not refilling as fast as need be and slowly run out of gas.

The engine slows to match the available fuel and runs at the lower speed.

If he were to reduce the throttle to a cruise setting for 30 seconds, the climb should return at least for 10 seconds or more.

You might have some crud in the carb fuel fitting or passage just before the Float Valve.

 

 

 

Hi Bill

I ran an electrical pump to the carbs to ensure proper flow of fuel. I then removed the carb bowls and check to see how much fuel comes through the valves, and the flow is good. I went so far as to rebuild the carbs and I put new valves in. 

Everything points to a fuel starvation issue, and like you said, retard to cruise and then reapply throttle, the RPM returns a little for a few seconds then dies again. Fuel starvation was the most obvious thing so I took a look at that first and threw every idea at this, and I have had no luck.

Strange thing, if I overpitch the propeller so that max RPM on the ground is below 6000, say 5800 to 5500 at full throttle, the RPM stays constant.