Im hoping for a bit of advice on a new project I have. I reciently purchased an AT-6 and a new TT .46 pro. I ran a tank full through per instructions and then another for good measure. at the 2.5 turns out of the needle which is supposed to be the starting point, the engine starts well but dies abruptly at about 2/3 throttle(lean I guess). Turning the needle out a couple more full turns allows it to get to full open but when I tip the nose up it dies. If i turn the needle out until it almost falls out I can get it to keep running with the nose up but it sags a bit. It wont run at all nose up unless the fuel tank pressure line is disconnected from the muffler. Im baffeled. The tank is installed per instructions. I have a reliable idle and good transition. Please let me know if you have any ideas. I am getting back into the hobby after a ten year abscence. Thanks everyone. Randy

Could it be tank placement? I know it's not as much of a problem as it used to be, but make sure the tank is aligned correctly with the needle valve.

Mike

It almost seems like you've got two problems there. The first being that the engine seems to be richer without muffler pressure (which is opposite to what it should be) which could only be a blockage in the muffler fitting, as if it's only got a pin hole to allow air into the tank. But going by what you need to do with the needle it seems there could be a blockage somewhere in the line. This could be anything from the clunk touching the back of the tank, a kinked fuel line or too small a hole drilled in the carb nipple.

I think Downunder has it. Sounds like an obstruction in the pressure system is causing a vacuum in the tank. The clue is it runs well? with muffler pressure disconnected. I'd look there first.
Good Luck.

Yea, put a clean piece of fuel tubing on the muffler fitting and blow in it to see if it's clear. Do the same with the Tank vent. Check the clunk in the tank to make sure it moves freely. And make sure the tank is protected with foam rubber to prevent fuel foaming.

Thanks everyone for your advice , Ill give your ideas a try as soon as I get a chance and Ill let you know what I find.

Randy

Watch your fuel line and look for bubbles flowing along with the fuel. I had the exaxct problem with a new 50SX, and it turned out to be a hole in my pickup line.

Jet

Did you figure out what the problem is? I am a fair newbie, but could it be a leak in the tank?

Zee

I havent had much time to get back to my problem yet but it looks like I am having problems with pressurizing the tank. Poor placement of the fitting on an aftermarket in-cowl muffler seems to be causing a possible vacume instead of pressure? Does that sound like it makes sense? Thanks for your interest. Randy

Rkrig,

I've heard that the pressure fitting should be close to manifold. My Mac's pipe has the fitting right after the bend.

Another thought is to start over with the installation. Many times just starting from scratch will allow you to stumble onto the solution. Double check everything. Make sure there is nothing blocking the fuel flow AND nothing blocking the pressurization (sp?). Make sure there is nothing in the fitting on the pipe that is blocking the air flow. i.e. piece of metal, glue, whatever.

Good luck.