zetor

My Feedback: (2)

My engine runs good flying inverted. If I do a hard outside loop my engine will stall. If I do 2 in a row it will sometimes die. I can do all the inside loops I want and there is no change in how the engine runs. I thought it might be a clunk line problem at first, but it will do the same thing if the tank is full. My clunk line doesn't touch the back of the tank. It sounds like it is running rich or loading up when I exit an outside loop and give it throttle. The tank sits a little below the carb. The engine is side mounted. Hard turns do not cause this.
The engine is an irvine 53.

FHHuber

Your engine is mounted up right? You have it adjusted just a LITTLE on the rigch side. one or 2 clicks leaner and it should go away.

If the engine is relatively new... it may not be cureable until the engine fully breaks in. Some engines thats over 3 gallons of fuel. The 2 8-oz tank break-in is really just starting the brek-in process.

zetor

My Feedback: (2)

It is side mounted. I've put about 3/4 gal. through it.

Woodsy

My guess is the clunk is'nt flopping around in the tank properly, on the outside loop the fuel is being forced to a part of the tank that the clunk can't get to

Skribnod

I have a similar problem with my rossi engine. On a hard pull up it will cut out for a second and then come back to full throttle. It has appr. 3 gallons of fuel ran through it and runs like a champ except for the hard climbs. Fuel clunks ok and no air leaks. I was told by the distributor the "G" forces are pulling the fuel from the carb and maybe a check valve on the exhaust side may help. Gonna try it this weekend and see how it works. I will let you know if it helps my situation. Any other suggestions would be appreciated. BTW these steep climbs are at about 100mph then straight to vertical.

JohnW

My Feedback: (6)

Could be the clunk, or it could also be that you have a very tiny air leak that increases during negative G maneuvers. Being a side mounted engine I don't buy the fuel being pulled out of the carb by excess G's. Might have a pinhole tear somewhere, could even be in the tubing in the tank. Normally, the pinhole stays sealed becasue it is so small. Under negative g's, the tubing flexes the right way for the pinhole to expand and bingo, air in the fuel line. Seen it before. Just replace all your fuel line (including lines inside the tank) and try it again. If it doesn't solve your problem, at least you know all your lines are good.

zetor

My Feedback: (2)

I thought it could be a clunk line problem too but wouldn't the clunk be forced into it's normal attitude during an outside loop?(to the back and down) I also tested this by doing one while the tank was filled. It does the same thing. I said it was acting as if it was running rich but what it is actually doing is leaning out. I was expecting a few more hits than this, but I guess that means it is rare. I guess the only thing left to do is replace the lines as John said.

Skribnod

I was told that on a high "G" maneuver that the pressure inside the tank exceeds the pressure the muffler tap is supplying. Therefore the air pressure escapes back through the pressure hose and thus draws the fuel away from the carb. Got my check valve from towers today and I'm gonna try it tomorrow and not wait until the weekend. I too have seen a small hole in the fuel line that causes problems every now and then but most of the time a fuel leak is visible and can be detected early on.

CafeenMan

You can make a check valve by putting a BB in a fuel filter. Won't seal 100%, but it works pretty well. I'm not sure what would be better though - copper or steel (as far as corrosion goes). I would guess copper would be better.

Stick Jammer

No. The clunk would be in it's normal attitude during an inside loop. In a hard outside loop, centrifugal force would push the clunk to the top of the tank.

CafeenMan

The G's on the plane will pretty much force anything that can move in the same direction. That would include fuel and fuel tank clunks.