The difference is aluminum vs brass. The alum. in the plane is clearly a smaller ID than the brass that comes with the DuBro stopper kit. The brass fits tighter in the stopper and the fuel line is snugger on the tubes.

Guys,
Be sure to check and make sure that the fittings that hold the fuel line between the remote needle valve and the carb are both tight. On both a .61fx and a .40fx that I own these fittings were loose causing air to be drawn in resulting in similar problems that you are experiencing.

Good Luck.

Hi,

Just another opinion??? If you are sure there are no air leaks and no splits in the tubing try this method to "get in the ball park" with low speed jet tuning.

Connect a piece of fuel tubing to the needle valve about 18" long and open the throttle. Have a small screwdriver in the slot of the slow speed adjust and blow into the tubing. Yes air from your mouth. Adjust the screw until the setting is such that you can just blow through it. Then follow the tuning tips covered in great detial in this thread, (bruce88213 for example). I had a new in box motor that was more than 1.5 turns out!!!!

Cheers,

Colin

Thanks for the info Colin. When I change the needle valve and inspect the one that's in there now I will check that line. And, I will start with your suggestion on setting up the low end. I won't be home until week after next so am getting anxious to get back to it.