Hi ALL,

I have set up a SuperTiger G.90 converted to gas using CH Ignition System and set up for crankcase pressure with Iron Bay Fuel Regulator with their one way valve, one tee for fuel overflow and using a Great Planes Gas Valve for filling tank.
Also have a fuel filter attached just behind the fuel regulator.

Engine is tuned in with High & low needle valves reasonably set....good idle , transition & high end all working fine.

The problem I am having is that after engines starts running, the fuel lines soon develop a lot of air bubbles which does not necessarily stop the engine from running but as soon as you move the plane from the horizontal position on the stand, and tilt the plane nose up it quickly dies.

Yesterday I took the wing off and removed the fuel tank & regulator, just letting them dangle away from the fuselage to see if excessive vibration from the fuse was the culprit. Still getting the same bubbles occuring....I even changed back to muffler pressure but same result.
All my fuel lines are new, fully engaged and secured with small fast ties. No fuel leaks in fuel lines or fitting observed and when overflow dot is removed, I get a wwhhossing sound which tells me I am getting good pressure.

What could be my problem??? I am totally baffled why the bubbles are occuring in a pressurized system like this?????

Any advice or suggestions at this stage would be most welocome.

DDriver.

What kinda carb are you using ???


Chad

Hi Chad,

I am using the SuperTiger G.90 standard carb (Twin needles for hi-speed/Mid range and low end/idle needle.

Although I am using the CH ignition, back in Nov 99, Gerry Yarrish of Model Airplane news did a preview of the Pro Soark Ignition on a SuperTiger 90 and it seems that the SuperTiger engines from .90 & up have twin needle carbs that work very well with the gas conversions.

I origionally had some fine bubble leaks around the hi speed needle, but teflon tape wrapped around the threads fixed that completely.

DDriver.

if you have bubbles in the fuel line this bublles come inside from two possibles sourses. one is the atmosphere an other is the presurized tank, the first can take place from lines or valves, the second from the line inside the tank, not more to think, bubbles come in in low pressure lines only. You can take the the complete system tank and lines to sink it in water and to give pressure him.