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Old May 04, 2012, 09:41 PM
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Black Hawk Renegade engine problem

Hi,

I have the above with a 18 Month old Thunder Tiger 46 pro. The engine has been really reliable in 2 other planes it has been in; a calmato 40 high wing and Alex Wittaker Jitterbug.

With the renegade I am having enormous trouble with it. It runs up, doesn't appear to have any problems but cuts out about 3 foot up after take off 8). Not nice . When it opens up on full it does seem to holding back slightly.

I did find some small particules in the fuel tank, and on the needle valve so I have taken that out and cleaned it, washed the tank out with clean fuel , replaced the fuel pipes.

I have to admit I am stumped now - my crazy theories and rantings in no particular order are.

1/ Engine is getting too hot and choking though no visible signs of burn off from cylinder. It is in a cowl but think I have enough of the cylinder exposed. Pictures on blog were before cut another chunk out of the cowl to allow airflow on to the engine.

2/Still bits in engine or pipes but have taken needle valve off again and seemed ok.

3/Air getting into the mixture somehow. I have seem some bubbles in the carb line. Admit to not liking the the tank on the renegade, its one of those bottle ones with the screw in the middle. Have not put silicon around the neck to seal it, and the fuel tube that goes to the carb does seem to have some play in it in that it can slide a bit forward and backward albeit stiffly.

So have to admit am not chuffed at the moment , the Renegade is a nice looking plane but cannot seem to get it in the air at the moment. It has a weak undercarriage block which I seem to be forever mending as deadstick just on take off climb is not ideal ...

Any thoughts and solution mucho appreciatedo..

Definately Mystifired
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Old May 05, 2012, 06:51 AM
WCB
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Very important on cowled installations: Make sure you have an air exit hole on the cowl that is 2~3 times bigger than the inlet. If not hot air gets trapped and the engine overheats. Also the fuel could be foaming in the tank from vibration causing the engine to lean out and overheat. Put foam around it to cushion it if you can. You shouldn't be seeing bubbles in the line.
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Old May 06, 2012, 02:53 AM
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...many thanks for the reply.

I don't think I have an exit hole, so I can do that immediately. When you say bigger then then the opening, not quite sure what you mean. I have a cut out around the cylinder head, and a hole around the the prop shaft. Is it the prob shaft hole the one you use for entrance hole measurement? On the bottom of the cowl there is a vent that I haven't opened up but will do.

The trouble with the black horse fuel tank is that it is inserted from the back of the compartment. It will be very difficult to place foam around it to cusion the vibration, as once I place the foam inside the tank will probably not fit. If I fit foam in so the tank still slides in then the foam is proabably not touching the foam and there the foam will not be doing its job of damping down of vibrations....

Still these are useful comments and my gut feeling is that the issues happen once the engine has been running for a bit, and also when the engine is at full power.

Well I will try these suggestions after mending the under carriage - Have to put supports underneath the under carriage plate as it is very weak...

Cheers

Mystifried
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Old May 06, 2012, 03:43 AM
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..actually I was talking a load of b****cks . There is no vent at the back. I have taken a few photos so you can see what the current cowl cowl set up is.

.... Also tank shots of the tubes and where and how it has to fit in ...... I did when putting the plane together shave down the foam collar that fitted over the head of the tank bottle. This thinking about it would potentially increase the vibration.

It seems to me there is some room for hot air to exit though not a clean air flow path.. Any suggestions ? (Both other planes had engine completely exposed so this issue did not arise...)

Mystifried
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Old May 06, 2012, 04:41 AM
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Mystifried

Is this nipple free, no dust inside?
Take a new,clean piece of fuel line and blow through it!!

Paint scheme is alright, cannot be the problem see second picture. I am thinking for a while about lack of exhaust pressure in the fuel tank, maybe something is blocking the route!

TF
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Old May 06, 2012, 07:24 AM
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Taurus and WCB,

Thanks for suggestions. Just taken it to club meet and we feel it is possible problems with the tank, (some of the plugs into the bung have movement). I have an older tank and the bung from that that might fit. Will also try to but some foam at the front to take out some vibration.

All lines not kinked where go into bung , have checked...

Will blow out exhaust nipple just in case then report back....

M
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Old May 06, 2012, 09:13 AM
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I see no cooling airflow over the base of the cylinder.
I have used the tank like yours alot with no probs...but you have to leak check it....to do that build the tank as if your ready to install it in the plane. get your fuel lines to the muffer and carb on as well. now submerge the tank in water keeping the end of the lines out of the water. put your finger over one line and blow in the other and watch for bubbles.
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Old May 06, 2012, 09:18 AM
WCB
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After seeing the pictures I see what you are saying. I was thinking that the engine was completely concealed inside the cowl when I said the exit needs to be 2 times bigger than inlet. Your setup looks fine. Tank position is a consideration. The center line of the tank needs to be in line with the needle valve or as close to it as you can get. This can be a real pain in an inverted engine installation. If the carb is too low, which is common in an inverted install, it will be hard to get the carb tuned properly. It has been my experience that 2 stroke glo engines are especially sensitive to the carb/tank placement. Others may disagree.
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Old May 06, 2012, 01:37 PM
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..well have put foam collar around front of tank, blow through exhaust nipple , and put extension on inside tank end of exhaust . Hope to fly tomorrow and see if makes any difference..

thanks for your replies

M
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Old May 07, 2012, 08:11 AM
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..how long can you run an IC engine on full thottle ?

Rained off today. But thinking about it, is there a rule of thumb. 30 secs , 1 minute longer. This is on the ground ........ thinking about the test to see if eventually fades ...

M
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Old May 08, 2012, 07:43 AM
WCB
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I don't like to run mine at full throttle on the ground for extended periods of time...not more than maybe a minute. The only air movement the engine gets is what the prop makes and will get hot pretty quick. A good test is to have someone hold the plane with the nose straight up at a 90 degree angle and run the engine at full throttle for a few seconds. If the engines starts losing rpm's or dies it is lean.
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Old May 08, 2012, 02:35 PM
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.. problem still there , not running up to full, choking then recovers when thottles back. changed needle value settings , borrowed a tachometer and detected no changes . Feeling is that dirt in Carb ...

M
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Old May 08, 2012, 07:35 PM
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I keep a can of WD40 with me in my pitt box. I'd suggest pulling the HS needle valve out and spraying some WD40 through the spray bar. If any scum is in there, it should blow it out. You said something about black bits, do you have a filter on your fill can of fuel? Since this engine has run before, I'm inclinded to think its the install. But I didnt see anything obvious in your picture unless there is a hole in your klunk line. As for bubbles, small amounts shouldnt be a problem, big bubbles are a problem. I had two TT.46 pro's used in a twin and they were great strong runners inverted. How about your fuel? How old is it, could it have absorbed any moisture? That will play hell with engine tuning.
Edwin
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Old May 09, 2012, 04:12 PM
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DON'T DO WD 40 ON AN ENGINE EVER!! It knocks the carbon loose, which then rattles areound, scores the piston, etc.

howell
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Old May 09, 2012, 05:16 PM
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I've done it often enough and never had a problem.
Edwin

2-stroke and 4-stroke
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