Another gas tank question
 

I was flying yesterday and the plane would die just about every time I stayed completely vertical more than a few seconds. My freind and I tuned on it, took the carb off, checked eveything. We ran it a litte lean, ran it a litte rich, and it still kept dying.

When I got it home I removed the gas take and that little clunker was stuck at the top of the tank. The tubing was bent around and I had to take it apart to get it un bent. I shortened a little.

Has any one else every had this problem? If so, is there anything I can do to prevent it from happening again? Is shortening the tube a good idea as I did?

Thanks,


Wings

RE: Another gas tank question
 

a couple things. one, when you have a problem, NEVER absolutely NEVER run it a little lean. you have probably worn the engine a lot by doing that, and there is a chance it will never run nearly as well again. second, DON'T SHORTEN THE TUBING. you want to get regular fuel tubing, get a ighter clunk, and have it hang about 1/4 inch from the bottom. unless it is a trainer, you never want the clunk to go up front because it it is pointed down enough to have ALL the fuel move forward, you are pulling enough negative gs that all the fuel is at the back of the tank.

RE: Another gas tank question
 

Thanks for you reply. I am not completely sure I explained the problem very well.

It is a trainer, but I installed the tubing exactly as the directions said. This puts the clunker where it can move up and down and back and forth at the back of the tank barely clearing the back wall. What happend with mine is some how the clunker made it to the front of the tank and got stuck. I shortend the tubing about 1/8" of an inch. It still goes almost all the way to the back corners. Its just a litte more than 1/8" from the back wall. So it may die a few seconds earlier when running out of fuel, and thats about it.

A lighter clunker may be a good idea. If the problem continues I may try that.

I do have a question about running it lean. I will admit I need to learn more about how to tune the engine. My freind flies all the time, so he kinda makes the adjustments and I ask questions. He told me it was a little lean, however there was still oil blowing out of the exhaust.

Is it possible to have the engine running too lean and still have oil coming out of the exhaust? Educate me please, lol.

I understand the book that comes with it. So, I am not completey ingorant. But like all things, experience is much more useful than reading the manual.

Wings,

RE: Another gas tank question
 

there is a point where it is too lean beyond question, and where it is a little on the lean side of acceptable. not hearing it run or putting it on a tach i dont know what it is. it could be that it is still fine and getting a good exhaust trail and oil etc. but should be richened up a bit, just to be on the safe side. getting the clunk back where it belongs should fix the problem you were having.

RE: Another gas tank question
 

Wrap a coil or three of solder around the base of the clunk where it has the fuel line around it. Use a small wire tie to keep it in place. Your clunk was light enough to drop forward in the tank. It's a relatively common problem in aerobatic planes, but not usually noted in trainers. Another way to add weight to the clunk is to slide a 1/4-20 nut over the fuel line at the clunk. Keep it place the same way.

Tune your engine to get peak rpm on the ground, then richen the needle 1/2 turn or so to lose a couple of hundred rpm. You want to be able to point the nose of the plane straight up and gain rpm without slowly decreasing rpm as the engine leans out. When you point the nose down, you want to maintain the same rpm as in a level position. The oil trail is not a sure fire indicator of proper mixture setting, but it's a start. Castor oil makes a smoke trail both rich and lean.

Set your engines' mixture when the tank is only 1/2 full, not completely full.

RE: Another gas tank question
 

Thanks for the info, I will try it if the problem continues.


You say castor oil leaves a smoke trail when the engine is both lean and rich. How about oil. When you see oil dripping out of the exhaust, does this happen both when its lean and rich also?

Wings,

RE: Another gas tank question
 

No no NOOOOO!

The problem that you had is not uncommon. It can happen as a result of an abrupt stop where the clunk get's slung forward, then gets stuck there. Adding solder to the clunk will just make it happen more often.

The way to prevent it from happening, is to cut the tubing between the tank stopper and the clunk and add a piece of stiff tubing (Plastic, brass, whatever).

Now, the clunk can still swivel around at the back of the tank like it's supposed to, but it can no longer swing forward.

RE: Another gas tank question
 

Cut the fuel tube in the tank in halve and insert a short length of brass tube (2-3cm) ensure it is a snug fit. This will allow the tube to move up and down yet prevent it tying itself in knots. The clunk should hang 1-2 cm off the back wall ( short of touching )
Yes there will be oil on a lean run ( though not for long!! ) this is why large numbers of people have converted to electric ( no mess) The methanol burns away and all you are left with is the unburnt oil and gunk.
Regards Steve

RE: Another gas tank question
 

Interesting point about shortning the line in the tank. I would have said to lengthing it so that it reachs the far bottom corner of the tank. I have done this with great success.

RE: Another gas tank question
 

A 1/2 turn open from peak rpm is a bit much for most engines. 2 or 3 clicks will usually drop the rpm 200 - 300.

RE: Another gas tank question
 

Thanks for the heads up. But for me, now that I've gone glow, I will never go back, lol. There is nothing at all wrong with electric, but the few I have seen/ flown are weak and flights don't last long. The power slowly peters out of the flight. I guess it probably gets much better if you buy all the higher end stuff like a brushless motor and top of the line batteries, but that really doesn't interest me. I love how my new glow trainer can just pull its self through any thing and you can fly about 20 mins. Refuel in 5 minutes and up you go again. Twenty minutes at the end of the day wiping it down is not a problem for me. Well worth it in my opinion. I just like the whole effect. It sounds like a real plane, lol. Stupid reason I know, but I guess thats what floats my boat.


Wings

RE: Another gas tank question
 

on a trainer the exhaust color should be pink. that means it is rich and you are on the safe side, but if it gurgles and sputters and trails smoke all the time it is too rich. tan oil is the best color for performance, but i assume you are not trying to extract the most power out you can. if the oil color is dark or even worse black, you have probably ruined your engine running the tank through that way.

RE: Another gas tank question
 

My oil color is dark, But I'm fairly certain my engine is not ruined, lol. It still screams through the air with authority. Do ruined engines do that?

I do appreciate advice, I sincerely do. But I can tell when someone may be offering words that aren't that dependable. For example a trainer's exhaust should be a certain color. Last time I checked there is no way to distiguish between a trainer engine and a non trainer engine, lol. I am just annoyed because you've implied several times that my engine may be ruined and it is definely not. If it were ruined I would be asking questions like why is it so sluggish etc. Not about the gas tank. I'm not trying to be nasty but please stop being so negative, its unreal.

I'm not an expert on these engines as I stated before. However, I am a mechanical engineer. I can't really see how running the engine out of fuel because of my tank being as I stated before, that this could "ruin" the engine. How do you kill your engine when you are finished flying? I bet you cut the fuel beings that is the only way to stop it short of physically stopping the prop. Well, this is the same as what was happening to me, I would go to vertical, the engine stopped getting fuel, it died.


Wings,

RE: Another gas tank question
 

Back to the tank question. Here's a pic of what I described earlier:

RE: Another gas tank question
 

Thanks Minnflyer,

That looks like the perfect solution. I already have my tank back in my plane now, and I had to glue the back stop in. So I will leave it alone for now, but next time it happens that's exactly what I will do.


Thanks a billion,

Wings,

RE: Another gas tank question
 

It wasn't running it out of fuel that could ruin it, but running it too lean, which is of course quite correct.

How he knows the exhaust color for trainers is another question entirely. I'm completely baffled by that remark.

RE: Another gas tank question
 

Ya, I guess you have a point. But it was running great till it went nose up, then died immediately each time. So I just flew it around level for the rest of the day. Loops and rolls didn't hurt either, it was only when I was nose up for an extended time. Either way, I appreciate the advice. My engine is ok thankfully.


Wings,

RE: Another gas tank question
 

I know others that have used MinnFlyer's clunk suggestion with success. Sometimes hard landings/shorts stops forces the clunk forward. Then you don't know until the next flight. So, the clunk position is usually the culprit. Other things to check if the problem persists;
Confirm that the pressure line tube (from the muffler) is positioned correctly. It should be bent upward to almost touching the top of the tank.
And, probably more important, confirm that you have no leaks especially around the metal tubings where they pass thru the rubber stopper....and leaks around the stopper.

RE: Another gas tank question
 

the oil color for trainers is a suggestion. pink oil means a litle on the rich side of acceptable. it is safer that way. i suggest it for a trainer because we are in the beginners forum andi suspect the guy hasn't been flying for years and years so it is just a precaution. when i became comfortable with my trainer, i leaned it out to top performance and it was just perfectly fine (about 300 below peak)

RE: Another gas tank question
 

Thanks for the info.

I flew it today. I read the instructions. I kept adjusting it so that when pinching the fuel line at fuel throttle the rmp's rose a little then quit. Thats what the book says to do so I should be ok.


Wings,

RE: Another gas tank question
 

What if your residue is blue/green?

Too rich? Too lean? Or just using Cool Power? :D

RE: Another gas tank question
 

The tank modification that Minn showed is the way to fix the problem. I've heard it referred to as a "clank" system compared to the normal "clunk". Don't ask me why it's named what way, but it does work.

However, most of us just keep in mind that the clunk can, and does, go to the front of the tank farily easily on some tanks. If you have a rough landing or hard stop for any reason, just pick up the plane and hold it nose-up. Then gently shake the plane back and forth. You should be able to hear the clunk rattling around. If you don't, give the plane a few hard shakes downwards and you can get the cluck to fall back in it's proper location. Since you have it fixed at the moment, you might consider just giving the plane a shake to see what the clunk sounds like when it's OK. Anyway, this happens all the time, most of us just live with it.

Minn, good one about the exhaust color :D. And then there is Byron and some other fuel blends that aren't colored at all. Obviously, that doesn't work very well.

However, the point that dark brown colored oil is usually a sign of running lean is valid. And black gunk is usually caused by metal being rubbed off somewhere, and if it's inside the engine it's bad news. (I most often see black gunk coming from a loose muffler or muffler tail cone). And if you do have a lot of unburnt fuel in the exhaust, you are almost certainly rich. However, I wouldn't set my engine by the exhaust color by itself, I don't think it's accurate enough.

A lean run now and again won't hurt an ABC/ABN engine. The liner expands faster than the piston with higher temps, resulting in a slow loss of power. However, a lean run on an iron pitson or ringed engine can cause damage, as the piston or ring expands faster than the liner with heat. If you run one of these lean enough, you can, in fact, trash it in one run, I've seen it done. But you have to work at it.

Oh, as far as killing the engine, I set my carbs so I can kill the engine from the TX. I think it's safer that way. Many engines come with a stop screw that you have to back out a bit to allow the barrel to close all the way. Oh, and if you close the barrel all the way, and the engine keeps running, you know you have an airleak in the carb somewhere. :)

RE: Another gas tank question
 

i wouldn't set my engine by exhaust color either. it isn't accurate, but if it is dark brown it is most likely lean. if it is pink, it is either rich or on the rich side of acceptable. tan is a good color. the black gunk is usually as montague said metal flakes, but if the exhaust is black as i said you may as well buy a new engine. that isn't just lean. you may as well be running regular gas.

RE: Another gas tank question
 

My engine still works! Its all good!:D

RE: Another gas tank question
 

My thoughs exactly!!!!!! [sm=lol.gif]