Hello guys,

I have a tower hobbies .75 and I can not get it to do a whole flight without shuting off in mid flight. So far I was able to proof that it was not the fuel tank. I have an Phoneix model Extra 330. I have a problem with the idle needle. I do not know the number of turns that it takes to set it to factory. So far what I have is in the Idle mix I have it a 4 turns out from close with the carb wide open. This is the only setting where i was able to turn on the engine and the engine was able to hold the idle but it is not smooth. If I close it 1/8 like the instructions say the engine will die after a few seconds of idelng I have the High mix at 2 1/2 turns out from close, and it is the same thing. The high is not smooth and I hear the engine getting Reach and Lean with out moving the throtle. If I close it 1/8 to 1/4 of a turn it dies after like 30 second. This is a replacement engine from TH and it has a brand new piston and slave. I used 1/2 gallon on the break in. I hope that you guys can help me.

Thank you in advanced
Carlos

If it is shutting off in MID flight, or at cetain attitudes of the plane, then either the engine is leaning out too much in flight, or you have a plumbing problem.

Once the engine is tuned properly there is no reason why it should die out when the tank hits mid level.

You should tune your engine with only 1/2 of tank of fuel or less, and also do a nose up and nose down test this way.

Even at 30 degrees nose down, the engine should continue to run ( test for 30+ seconds ) albeit a bit slower, and at 90 degrees nose up ( test for 30+ seconds ) a bit faster.

In every situation I've seen like this, the problem has always been plumbing.

In turn that can mean, an uncovered clunk, insufficient tank pressure, or too much flow restriction.

Insufficient tank pressure can occur because the muffler nipple will get clogged with debris, but this also manifests on the ground and usually at all tank levels.

Don't try and tune to max an engine that doesn't have 10 or 15 flights on it.....the engine maybe so out of tune that you would almost have to be there to see/hear it to tune it......shutting off in the air is a sign of too lean...or fuel line/tank problem......
I'll tell you the best way to tune.....low end first....pinch the line to the carb with the engine at idle.....it should run for about 5 seconds or so before you hear a pick up in rpm (leaning out due to the line pinched) and start to die...release the line......and the engine runs as before....if it revs up too soon you're too lean and you need to richen the low end...if it runs forever then your too rich and will cause coughing and burble going to high power......once set go to the high end...go to high power and what ever you do watch that PROP.....richen first , you want lots of smoke and may even be spitting oil....lean it out and you will hear an increase in rpm...as you lean, rpm will increse until it maxes out....from there either way you go is less rpm...now richen it a 1/8 to a 1/4 turn......retard power to idle and re check the low end........once good let it set at idle for a couple of minutes...don't jam the throttle to max..but advance the the throttle firmly to max...the engine should transition smoothly to high power.....all done...
make sure there are no fuel issues.....find out the factory settings by calling tower...and tune from there.....good luck

I have a few TH 75's and a TH 60. They do not like to be run rich. Tuned correctly, they run like clockwork.

I am afraid that you are too far off and it is time to start over.
http://www.towerhobbies.com/products...owg0175mnl.pdf

Pull the carburator off and adjust the low end needle per Tower's instruction by looking up through the throat from the engine side. There you will see the mixture needle and spray bar. Adjust these per the instructions. Don't leave a gap though, Tower has posted on their webpage that there is no gap.

Another good trick is to pull the carb and hook up a clean fuel line to the fuel inlet. Fully close the idle needle screw  by turning it clockwise until it stops. Now slowly open the needle screw while blowing air into the fule line with your mouth. As soon as air starts to pass through, stop. This is a good starting point.  Reassemble the carburator onto the engine. Start with the high speed needle at  2 turns out. Fuel up and make sure you are not flooded before starting up. Your needles are set very rich and the engine should start quickly.

Set the high end needle first. Turn it a few clicks at a time listening for the engine to gain rpm. When you think you are close, pinch the fuel line. If it dies quickly you are too lean, richen a little and try again. If it picks up rpm you are too rich, lean it a few clicks and try again. When you have this set shut off the engine and let it cool. If you have a tach, use it. They make tuning much easier since you can watch the numbers climb or drop.

Start it up again and run it up to warm it up some. Lower the throttle and let it idle for a full minute. If it slows down and dies then lean out the idle screw 1/8 turn. You can also pinch the fuel line at idle. It will take longer for the engine to be affected, but you will tell if you are rich. Keep leaning the low end until it maintains idle for a minute or more. Now run it up and drop it back to idle. Let it idle for a few seconds and then go wide open. The engine will stumble if too lean. Richen it up a little and try again.

Now have someone hold your plane pointed up at full throttle. The engine should not slow down or die. It is ok if it speeds up, a little. If it dies or slows down richen the high speed needle three clicks and try again.

You should be set to fly. Remember that the low end only needs to be turned in 1/8 turn increments or less. Once the low end is set you should not have to change it again unless you change nitro blends. Even then it will only be a small adjustment.  Those are the basics of glow engine tuning.

Thnak you  playntraffic the thing is that as you know the carbs in the TH 75 have a spray bar that goes from wall to wall in the carb with a little hole in the middle. Inside that spray bar is where the Idle needle goes and you can see it when you screw it in. All the instructions from tower are wrong and I can not belive that they have not update it after so many years. I  am looking to get the settings in turns. I do not like to guess the initial setting and that is what I am doing now. I did the tunning as per their page but when they say there is no gap I can tell you that either I am not understanding what they mean or that they are wrong. Also the instructions that say that the gap is 3/32 to 1/8 is also wrong because the little hole is not that big so that setting can not be used. That is a setting that can be used in an OS engine where you can see the gap and from the top but not in this one. 
I will keep playing with it but if someone can give me the starting set up in turns I will really appreciate it.

Thank you
CC

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I don&rsquo;t have tower hobbies motor yet but I had dead sticks because of a clunk that was bent and held against the tank wall.
I figured it by shaking the airplane and not hearing the clunk, try to see if that is the case.
I shacked the airplane more to release it and no problem any more.

Alex

Turn the throttle all the way closed as far as it will go, then back out the needle to more, and see if you can close the throttle still more.

Don't force anything.

Once the throttle will not turn close any more, turn the LS needle in up to the point that it stops. Again be gentle. You do not want to score the needle itself.

Now turn it back out about 3.5 - 4 turns. This should leave the low end rich and you should be able to start the engine using a HIGH idle.

Then adjust the HS and finally the LS to get a more reliable lower idle.

I have seen them leak air around the carb draw bar. I take a small amout of clear silocone on my finger and force it into the side of the bar with out the nut. Good luck..

I i have a second TH.75 that  I installed a new Piston and sleeve. I can not get that engine to run. I am 4 turns out on the low end needle and 2 turns out on the High speed needle. It is super tight and I have tried the heat gun to the head of the engine and still very hard to turn. Once I got it to run for like 3 second and it turned off. I haven't been able to get to run again. I checked the plug and it is getting heat. Help!!!! I have a P51 waiting for this engine!

Thanks in advanced

Is it tight because of piston to sleeve friction?
is it also tight when the glow plug is out?

Set the LS needle about 3 turns and the high speed needle about 3 as well.

Prime the engine well, and make sure that fuel is hitting the carb not just the remote HS.

Keep your lines as short as possible and be sure that the muffler nipple is clear and pressure is getting to the tank.

Did your engine run and speed up during those three seconds and then abruptly stop?

Or did it run sluggishly and slowed down to a stop?

I would bet that it got a bit of fuel ( which is why it started ) but not enough flow to sustain the run, so it shut down.

Lack of pressure, air in the lines, a misplaced clunk, etc. can all account for this.