I have a Blackhorse Cub. I have mounted my evolution .46 on it and I'm having a hard time to get it to run properly.
It seems to have a problem getting a constant fuel flow. I would have to plug the exhaust / crank the engine over to prime it and then it would run. all lines are good and can be blown through with ease.
I installed a one way valve to keep fuel pressure in the line ( helped a little)
I disassembled the muffler and pluged 2 of the several holes in the restrictor plate. (Helped more)
when it is running at WOT it may run good for a minuite or so, other times it surges and may die.
Idle is usually not a problem, but sometimes it will lean out, others it loads up.
It may be just luck of the draw, but when it is running and i lift the plane and run it upside down, nose up, nose down, ETC and then place it level it seems to run fine for quite a while.

I have noticed that the carb is 1/4 of an inch directly behind a small section of the cowl. It is open above and below this. Could this be screwing up the airflow into the carb ?

I dont want to cut the cowl to find out it was not the problem.

Any input or sujestions would be appreciated.

FRUSTRATED.

The problems people have with inverted engines are USUALLY caused by one of the following:

1. BIGGEST PROBLEM - make sure the outlet line (fuel supply line ) AT THE TANK is within 1/4" of the SPRAYBAR in the carb. Often, this requires modifications to the airframe in order to get the tank at the correct height.

If the tank is too high, the fuel tends to siphon out through the carb and MAY cause a rough idle and poor transition.

If the tank is too low, the engine will frequently exhibit symptoms similar to yours.

2. Flooding (and hydrolocking ) of the engine. This caused by excess fuel collecting in the head and not allowing the plug to heat up. Be sure not to over prime the engine when starting to minimize the flooding. Many people have the engine mounted at an angle to avoid this problem. 2 strokes are more suseptable to this than 4 strokes.

I HIGHLY suggest using a remote glow ignitor with an inverted engine. That stops you from having to reach under the plane to remove the glow ignitor (also saves the fingers and hands )

Thanks for your assistance.
I will compare the tank output to carb level.
With the evolution head being angled I can get the glow plug from behind.