I have the Brison in a new Carden Extra 300 and has four or five flights on it. Engine runs great on the ground and when flying except when I do a vertical dive after a stall turn. The problem is when I pull out of the downline the engine will die or not respond to throttle input for 15 or 20 seconds. On one flight the engine wouldn't respond. When I landed the engine was still Idling and finally throttled up. The clunk in the tank is ok. Any thoughts on what might be causing this problem? Low end to lean or too much cowl pressure causing carb. to go rich?
Thanks
Carroll

Sounds like dirt in the carb to me. Any time you oopen the carb. if the engine gets the fuel it will speed up. if the carb is open and not speeding up then its not getting fuel.. "Ken....The "BALSA BANDIT"

If your engine only does this in a nose down position, chances are your clunk is staying at the back of the tank and is sucking air during the dive. Check the supply line in the tank, I bet you find it is too stiff.

Thanks Tommy, You are right, I pulled my tank and the klunk line was sticking straight up and wasn't falling down like it should but I really didn't think that the engine would burn out fuel that was still in the line that quick. I am using the Blue Line 1/8" fuel line for the klunk line. Is this too large a line?
Thanks for your feedback
Carroll

Carrol:

You got me interested so I did some math...with 1/8 inch ID fuel tubing that is 12 inches long the volume of fuel in the line would be .589 cubic inches, and that would be .326 ounces. If you had a burn rate of 2 ounces per minute, there would be 9.78 seconds worth of fuel in the supply line. Say 10 seconds give or take. Is that about how long it takes for the engine to start acting up? To me, that seems like a long time to be pointed down, but I don't know how high you are and how fast you are coming down.

Of course, if the line has less than 1/8 inch ID, then things go to hell in a hurry. If the line had an ID of 1/16, then you would have only 2.44 seconds of fuel in the line, since the volume of the fuel in the line is inversely proportional to the square of the diameter. If the line was swollen, then it could very well have a reduced ID.

See what happens when you ask an engineer a question?

WOW who was that masked man

? Are you using silicone on a Gasoline engine? That can be your problem as that happened on a P-51 I bought RTF Tygon on the outside of the tank and silicone on the inside. Just a Thought.
Lee

Tommy, My downlines are not more than 5 or 6 seconds at the most and a couple of times I thought the engine had died as I leveled the plane to horizontal flight, but as soon as I landed I noticed the engine was still Idling and throttled up and eveything was fine. But yesterday It simply quit. Thats the reason I thought that maybe the engine leaned out or loaded up during the downline. Could pressure in the cowl have caused the diaphram to load the engine up? The cowl is opened up quite a bit though and seems like if this was the problem, It would be the same at normal flight at full throttle. I did remove the klunk line from the tank and the line when out does fall on over as it should. So my doubts are in the fuel line setup. I guess trial and error will eventually tell all in this case.
Thanks for the feedback,
Carroll

Carroll:

Two thoughts:

1) If it is a clunk problem and the line is drawing air during the down line, then a longer line would give you more "reserve". You could just put in a fuel supply line with a couple of loops in it to give more length and see what happens. Even though the clunk line is moving, it may still not be moving forward far enough. The carb will draw through quite a length of line without any problem.

2) It may indeed be a pressure change on the carb diaphragm. One common cure for that is to vent the diaphragm chamber to the inside of the fuselage so it will see the same pressure all the time. You will have to solder a small tube or nipple on the cover either on top of the existing hole or plug that hole and make a new one for the nipple and run a line from the nipple into the fuselage.