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Thunder tiger 91 mounted at 225 deg. dies

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Thunder tiger 91 mounted at 225 deg. dies

Old 07-11-2012, 02:15 AM
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ABORH
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Default Thunder tiger 91 mounted at 225 deg. dies

I have a relatively new thunder tiger 91 pro 2c mounted at 45 degrees off of inverted midline that stalls especially when in the mid range of throttle travel. I have had 3 dead stick landings out of four flights. The engine is run on 15% nitro with a castor/ synthetic blend. It was broken in carefully on the bench. It has about 1.5 gallons of fuel through it. Prop is 15x4w. Plug is an OS #8. I have mounted .46 2c engines like this w/o difficulty in the past. I have leaned out the low end with some improvement in that it seems to take longer to die. Perhaps I need to lean it out further? I do not believe it is over heating. It will idle all day at 2600rpm. It will run at full throttle 10000rpm, completely draining the 16 oz fuel tank. I have read that a 4c plug can help but have not yet tried that. Are there other suggestions? I have a friend with the identical problem with a similarly mounted .30 4 stroke and OS 91 FX. Is it the 225 degree mounting position?
Old 07-11-2012, 05:42 AM
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cymaz
 
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Default RE: Thunder tiger 91 mounted at 225 deg. dies

Try an f type......it won't hurt. If it coughs, splutters and dies it will be rich. If it just cuts will be hot. Make sure you can see a small trail of smoke (not too much), smoke out heat out.

If it at idle on the ground for 10 secs and then immediately WOT if it coughs and splutters too rich, lean the low speed needle JUST A 1/16 OF A TURN. Then readjust the high end to 2 clicks off max revs.....keep doing this until it picks up well when you kick open the throttle.

If on the other hand after 10 secs idle it cuts at immediately WOT then richen low end needle and adjust the high speed needle as before.
The twin needle set up is a balancing act between the 2.
Old 07-11-2012, 05:53 AM
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Default RE: Thunder tiger 91 mounted at 225 deg. dies

Try a hotter plug or more nitro in the fuel. The Tunderbolt plugs from Hobby People are extra hot. Or an Enya #3. No need for 4 cycle plugs extra hot 2 stroke plugs work better and are cheaper.
Old 07-11-2012, 07:13 AM
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SeamusG
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Default RE: Thunder tiger 91 mounted at 225 deg. dies

Where is the fuel tank mid-line relative to the carb's spray bar?
Old 07-11-2012, 07:42 AM
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Default RE: Thunder tiger 91 mounted at 225 deg. dies

I know where you are going with that, but he is not having trouble restarting the engine. My experiance is that you can set up an engine in the inverted position with a too high tank level, but it drowns in fuel when shut down and is flooded when restarted. Runs fine but restart is bad unless you clamp off the fuel line when off as the fuel will siphon through the engine.
Old 07-11-2012, 11:06 AM
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Default RE: Thunder tiger 91 mounted at 225 deg. dies

Thank you all for your suggestions...It seems as though I need to spend more time with the engine fiddling with the needle valves.... I will try that first. The engine has the "sputter and die" action so I will lean it out little by little. Idling on the ground fore about 10 sec and going to wide open throttle produces a very nice transition, actually. That is why I am at a loss... any way, I just don't have it right yet.

If that does not work, I will go to the hotter plug. I usually fly 4c so I have many 4c glow plugs.

I understand about the fuel tank location. I forgot to mention in my description of the problem that the carb is just slightly below the mid line of the fuel tank. I have not had a problem with flooding.

I will post the results of my further futzing. The engine is in an old VectorFlight Sukohi that flies beautifully when the engine is running
Old 07-12-2012, 08:16 AM
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Default RE: Thunder tiger 91 mounted at 225 deg. dies

Hi!
There is your problem! Tank is to high ...or carb to low!

But why on earth use 15% nitro when all it takes to have nice throttleing /running engine is 5% nitro.
Do not use a warmer plug!
If you use as much nitro as 15% you could use a colder plug than the OS 8,but not a warmer plug and certainly not a an OS F plug. Warmer plugs are used when you run less nitro or no nitro at all...or have less compression.
The OS 8 or Enya 3 or 4 plug will work good with 5% as well as 15% nitro.
So...Lower the tank and set the low speed needle and you will see that your engine will work just perfect.


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