O.K.-Question on fuel tank set up for aerobatic planes such as G-202, Extra,etc. Has anyone experimented with longer clunk lines so that the clunk will travel to all four corners of the tank? Longer meaning approx. five inches in length to allow the cluck to freely travel in the tank. I am currently flying a Great Planes G-202 with a Saito .91, I have a good tune up on the engine, yet every once in a while during a long verticle drop, the engine will flame out. This only happens during verticle drops. This set up will idle at 1950-2100rpm for more than three minutes then throttle up with no issues.

i would split the line in 1/2 and intall a piece of metal tubing in between the 2 halves to make it move better. I have never had to do this as all of my glow will not flame out in loops. So this is just a guess suggestion.

Not An issue during the beginning of the flight, only when its getting past eight minutes or so and the fuel is about 1/3 to 1/4 tank.

how large is the tank?

Tank is 16 oz.

Some people use a very flexible line to the clunk so that the clunk will follow the fuel into the front of the tank. If you do this, make sure that it won't get stuck inh this position.

Gulliver-Thanks I haven't bee able to find any really pliable tubing-FYI I learned to fly in Boulder back in the late 90's at the Res. Had a great while flying there.

Try a small hearder tank. That should solve your problem.

I do not know what a hearder tank is!! Care to offer an explanation??

Sure, A header tank is a second small fuel tank (perhaps 3 oz in your case) that you plumb in between your engine and regular fuel tank. The purpose in your case is to keep one of the tanks (header tank) completely filled with fuel at all times, thus less likely to suck air. Do a search on here for "header tanks" and you should find some photos of set ups.

Here's how you plumb it:

>Run the fuel line from the carb to klunk line of the header tank.

>Run the vent line from the header tank to the klunk line of your regular tank.

>Run the vent line of the regular tank to the exhaust nipple.

What will happen is the header tank will stay almost completely full at all times as that header tank will not fill with air till the regular tank is dry.

Notes:
Since you are running a glow motor, try to keep this header tank (and the regular tank) as close to the center line of the carb if possible. Also, keep in mind the header tank will give you usable capacity so you can also decrease the size of your regular tank by 3oz if desired to save weight/space.

Also, place this header tank in front of the regular tank and keep the lines as short as possible. You want to try to avoid any lean situations caused by fuel draw restrictions (as on any glow motor without a pump)

Hope this helps..............Mark

I recently had a situation on my Moki 1.8 glow where after buring a half tank the engine would go lean on uplines and want to flame out if I didn't come out of the power.
I found a very slight crack in the mold line near the rubber stopper that would weep the fuel out (barely)when full (no chance to lose tank pressure) but then begin sucking air at some point where the flame outs woud occurr or want to.
I am not saying it will fix your problem, just FYI info while you are troubleshooting. This fuel tank is only 3 inches from the needle valve and it runs flawlessly now.

I run a 16oz Benett tank on a 88" Yak with a 50cc motor. I find this to be the best 16oz tank on the market right now.
Granted it's not a glow engine, but keeping the same sound principles, will save you a lot of hassle.

All your metal tubes should be sanded so they have no sharp edges. They should be brabed as well so the tubing has something to hold on to. After installing the appropriate tubing, I use very small zip ties to secure each tube behind the barb.

The line going to the carb need to reach inside about half an inch of the end of the tank (when suspended). If the tank has a funny shape, use common sense. Do not use ARF tanks as they are ofter low quality (though some are provided with high quality tanks).

For a clunk, I use a ceramic filter that works really well (Don's Hobbies). The little cluks provided with ARF tanks someting do not have enough weight to bend the tube.

After installing the stopper properly, I put a bead of silicon around the base.

Do not use the various fuelers provided, they tend to develop issues over time. Nothing beats a proper fuel button that has a tube that connects to the carb line using a proper T fitting (2 line system) and properly secured.

I have run several 4 stroke, non-pressurized engines this way with no issues...

I run a Saito 180 and don't have this problem. I think you have another issue somewhere and I would replumb the whole tank and probably replace the tank. Are you too rich on the low end which would burn a lot of fuel? Also, try replumbing with the large tubing which would give you move of a reserve on the downlines.

I would check the fuil line it mite have A hole in it when fuil level is high no problems as the fuil goes down during the flight the hole suck air you lean out and the motor dyes. I also like to use A large clunk it follows the fuil better. Most 4 stroks like to run rich at least my YS 63 and my YS 140 that is and they love 30% heli fuil. I hope this helps good luck.