@ Less hum thats interesting that air could go threw that way. I will try when i get time. I also have went threw an checked every bolt/screw on the engine to see if any was loose. The la engine after a few runs had several loose but this 55ax... had none that was loose. Gosh i hope i can figure this out soon. Well got to go am at work on my phone.. doubt i be able to post back tomorrow have baby doc appointment after work. Thx jo

First thing I'd do is get rid of the third fueling line. They are the source of lots of problems. Next make sure the pickup clunk is short of the end of tank, hangs to the bottom and moves freely. Pressure line from exhaust should vent to top of tank. Check for leaks. Hold it up to light and bend it around to look for hair line cracks. Leaks are common at hard line connections. mount the tank high enough and insulate with foam. When you prime it to start set at full throttle hold your thumb over the exhaust and flip the prop until you see fuel flow into carb with no bubbles. this will let you know the pressure side is good. To check your vacuum, hold your thumb over the carb and flip the prop, fuel should flow to carb almost immediately with no bubbles. Don't worry about anything else until you get solid fuel flow to carb without bubbles,
Scott

"Less hum thats interesting that air could go threw that way"

We got so that we would not even try out a new engine without doing that.

Les

Jo we'll hang here until we fix it......I build airplanes for people,and that's one of the things I do religeously,is different colored lines.
common sense tells us that you don't have to be concerned with the 'pressure'line from the muffler,because it's full of air any way ,and can't cause that problem.
Now you only have two lines to care about,and that's the 'fill' line..and the one to the carb.
The oldest trick in the book is to take the entire system and put it under water.
plug any two lines and blow through the open one, in rotation.once all the lines have no bubbles.that's not your source of trouble.
If your tank is full to the top,and you're getting bubbles,it'll be fuel foaming,most likely.....try a tank of someone else's fuel.
You can't get bubbles in a pickup line,unless that line has a hole,or the fuel is foaming.and it doesn't matter what's happening with the carb right now.

However,I have had the pressure line and the pickup line so close together,the incoming air ricocheted right into the pickup tube....no holes ,no foaming,but AIR.
you may just need to relocate one of the lines.

I JUST remembered another one. On one of the rubber stoppered tanks I had, if you tightened down the center screw holding the, plastic ends/rubber stopper sandwich stopper, assembly together, too tightly, it would distort the assembly, and cause leakage.

Les

Okay i replaced all lines put in bowl of water blew in (capped the other 2) no bubbles... I installed the tank tried to fuel an it was like a pressure can an blew fuel line off.. (i had fuel line clunk at bottom orientation, its like a triangle setup) moved it around an found it fueled up with the fuel line at the top (clunk still hits bottom) installed fueled started an ran... it will run fine till you get to 1/4 throttle an just dies. The needled valve has absolutely no effect in the way the engine runs it seems. (the LA engine was so easy to here the 2cycle sound then the 4 stroke then back it off a little an its ready to go... The 55AX was like that on the test stand just not now) anyhow 1/4 throttle it dies.... the fuel line I have is a little more blue an not as clear as I thought it would be so I can not really see fuel moving threw or if its still getting bubbles or not... back to square one again

schusterjo,

Take the caburetor apart and check it.

While taking it apart look for some dirt particle.

My suggestion is based on your statements.

It appears that the mixture becomes improper when you try to rev up.

You would not do any harm by having a good look.

Zor

If needle valve adjustment makes no difference to the engine running, I would say it's either blocked or leaking air badly. Like Zor says, take it apart and check it out, and clean it.

Originally Posted by Zor

schusterjo,

Take the caburetor apart and check it.

While taking it apart look for some dirt particle.

My suggestion is based on your statements.

It appears that the mixture becomes improper when you try to rev up.

You would not do any harm by having a good look.

Zor

Originally Posted by abenn

If needle valve adjustment makes no difference to the engine running, I would say it's either blocked or leaking air badly. Like Zor says, take it apart and check it out, and clean it.

Ya thats what OS tech support suggested as well.. Got it apart an will be heading to store soon to get some carb cleaner to clean it out...

While it's apart, check for wear or damage to the needle. It should go to a nice point, and the point shouldn't be bent. Replacement OS needle valve assemblies are readily available if you suspect anything's amiss there.

Originally Posted by schusterjo

The tank I replaced it with already had fuel lines on it thus "different" fuel lines... as mentioned the tank I used to replace the old one was the tank I used to break in the engine on the test stand... That means it at the time of testing had proven to be a good tank an good fuel lines, kinda eliminating both possibilities at the same time by using a "known good tank an fuel lines".......................

Coming from one who tests very large software applications... Just to note.... having a good tank and fuel lines on the test stand does not guarantee the same following install in a plane. the fuel lines more often than not get holes from running through the firewall.. tugging, etc..

Got it all together seems to run fine now... only issue I am having now is that i can't fill threw the fill line, I have to use the line to the carb to fuel the tank or it will not fill... if i use the fill line one of the lines will blow off, that pressure can effect again, strange... Anyways little windy for a "test" flight so i will try soon.

Sounds like you got your fill and exhaust line mixed up. Tank air should always vent freely out the exhaust line until full if installed correctly

Okay got it.... I just took it out for a flight (still a little windy but went for it anyways) an it flew great. 55AX has tons of power for this plane an was fun to fly in the wind with the extra power. I did however change the tank configuration around again this morning before the flight. After reading this nice long article I choose to go with the uniflow tank setup http://www.fraserker.com/heli/uniflo...flow_works.htm
2 clunks, one of lines about 1/4" shorter the the other in the tank, the shorter being the exhaust (pressure) an the longer being the fuel (carb) the vent is at the top of the tank an I ran the hose to the bottom of the plane for fuel to flow out during the fueling an it reaches full (overflow) of coarse keep this line plugged unless your fueling. I choose this because the lines are in the open an not under a cowl, seemed to be a better way for this planes setup (easy access to lines for furling).

Just wanted to say thanks to all who helped an im sure i will have other questions an problems soon for you all to help me with...
Thanks
Jo