Need some advice here guys.

Its a Seagull PC9 with a Thunder Tiger .46 mounted inverted.

When starting the engine, it idles fine with the glow plug ignitor. When I take off the ignitor, the RPMs go down quite a bit.

The first time taking up the plane..It ran fine.. The second time, I did a low fly by and heard the engine reving and going back down.. I figured it was getting hot and cooling down.. Brought it back in, took the cowling off. It ran fine for another flight.

Well, it dead sticked twice with the same symptoms.. Low fly by.. I heard the throttle gradually decrease on its own until it was dead stick. The 3rd time I heard the throttle decrease on it own, I put the throttle at 50% and it stablized so I could bring it in.

Well, yesterday, I decided to go back out. First flight was fine. Second flight, idle and throttle up were fine, but as soon as I took off the throttle started going down. Brought it back in. Put it on the ground and started it.. Put it at full throttle and had someone pick it up and point it upwards. Everytime it was pointed upwards, it wanted to die.

I adjusted the high mixture control, and no luck. Any ideas?? I've had people suggest I was getting air in the line, bad fuel, and all kinds of stuff (none of which I feel are the actual cause).

it might be too lean. Start up the engine. Have someone else pick up the plane, give it full throttle, then have the other person hold it veritcal up, then down. if it starts to die it is probably too lean

I realize all this may sound "Mickey Mouse". You have a lean condition. It can be caused by not having the high speed needle set properly, foaming, a pinhole/airleak in one of the lines, clunk hanging, etc.

If your low end is OK (idles and transitions to full throttle OK), peak the engine with the high speed needle, then back off 1/8 - 1/4 turn. Now try your nose up test - it should be OK. If it is still giving you problems, replace ALL the fuel lines both INSIDE and outside the tank. Also make sure your clunk can move freely and is not hitting the back of the tank. I am assuming you have the tank wrapped in foam to minimize/prevent foaming and you have the line from the pressure tap on the muffler connected to the tank.

One other thing - if you are running a Pitts style muffler, try blocking off ONE of the exhaust tubes. Many Pitts mufflers do not provide adequate pressure to the tank (JTec is well known for this.)

I messed with the high speed needle without much luck.. I did change the fuel lines to carb exhaust and filler because I was using large instead of medium hoses.. The hose inside the tank to the clunk is still large size. Could this cause problems?

Also, I noticed when I unplug the filler line, the fuel streams out.. Is this normal?

Also, the tank is quite a bit higher than the carb, can this cause problems.. Here is a photo:

The fuel running out is because the end of the fuel line is lower than the clunk inside the tank. It is siphoning out.

I would replace the line inside the tank with medium fuel line.

The tank being substantially higher than carb can cause flooding and "hydro locking" on inverted engines. Ideally, the fuel supply tube coming out of the stopper on the tank should be at the same height (withing 1/4" - 3/8" ) as the spraybar inside the carb.

Based on your initial post about the engine about the engine rps dropping quite a bit (about 200 rpm is normal) you may have a marginal gloe plug. Another possibility is that the engine may be overheating.

Is it worth, lowering the tank down and drilling another hole in the firewall to run the carb feed line so its straight out to the carb instead of down and then up?

You really want the center line of the tank even with the barrel in the carb.

If you can lower it, I would.
Dennis-

Did you try changing the plug?

A buddy of mine from the field figured it out.

We were getting bubbles in the fuel line to the carb.. I had an APC 11x6 on it and it was vibrating too much.. Put a Masterscrew 11x4 on it and no bubbles..

Make sure you balance those props! Manufacturer shouldn't matter. It sounds like the APC was way off balance, and the MA is closer. But you should still balance it. I've never seen a prop that didn't need a little bit of adjustment. Even the 10 inchers.

That was the odd thing.. We did balance the prop.. We took it off right before we put on the MA and it was balanced..

That is odd. Try a few drops of Armor All in your gallon of fuel. It stops the foaming, and might eliminate the bubbles.

Also just a bit of foam around the fuel tank works wonders.... I make sure to put a piece on the front of the tank as well where it contacts the firewall.

Andy