lippitdoo

I am having an issue with tuning my .46 evolution engine. I have noticed that when I increase the throttle, bubbles develop between the needle valve and the carburator. Which when that occurs the engine will die. The needle valve assembly is brand new. I took it off and closed it and blew threw the hose and it is air tight in the closed position. When I open it it will begin to allow air through it, but unable to tell if it is leaking in the valve assembly. What else can cause this problem.

alfredbmor

One thing that comes to my mind is the fuel tank, some tanks promote bubbles as they get shaken by the airframe (as you increase throttle), and you may solve this (if this happen to be problem) by isolating the tank from the airframe with foam pads.

mscic-RCU

My Feedback: (6)

are there bubbles in the line from the tank to the needle valve? if so, try isolating the tank with foam rubber, replacing the line from the tank to the valve. if there are no bubbles in the line from tank to valve, try replacing the line from the valve to the carb.

weldercde

I had the same troubles . what we did is moved the needle valve to the carburetor. It fixed the problem. I also had to replace the o-ring on the needle valve.

turdfergerson

I also had the same prob, not sure if it was the tank or the fuel lines but I put foam under the tank and replaced the fuel lines, also another prob I had was the four cap screws on the back of the motor were backing themselfs out, so i removed them one at a time and put thread lock on. once all that was done she was a great running engine until the day that i put her into the ground!!! now shes in a new plane waiting to fly again... good luck.