Have a Thunder Tiger 42 GP with a 10x6 APC and using 15% fuel.

Engine was broken in according to instructions and has about 7 tanks though it.

Here is the interesting part, the high speed needle leans out at peak rpm about 3/8 of a turn from being fully closed.

Seems a bit much????

Also, cannot get the engine to idle steady. It speeds up, slows down and when I raise the nose of the plane at idle it dies.

Have tried all different setting on the low speed screw adjustment and it runs better with the low speed adj screw turned all the way in clockwise.

When at idle I push the nose down and it seems somewhat better.

I replaced the tank and fuel tubing and still have the same problem.

Also replace the glowplug, same problem.

Tried different fuel, same problem.

Tried different tank heights/locations, same problem.

Seems as if the engine is sucking air from somewhere, but yet it has excellent compression.

I tightened all screws/bolts on the engine as well.

I washed the carb and high speed needle too.

ANY HELP WILL BE GREATLY APPRECIATED IN MY DILEMA.

Dave
from PA.

Dave,


You are using the maximum recommended nitro percentage. If you don't need this much power and 200-400 RPM less can be spared, get some 5-10% nitro fuel. Your engine will run cooler.

The instructions are not perfect; it shouldn't be broken-in very rich.

For an ABN engine, [link=http://www.rcuniverse.com/forum/Tapered%2DBore_Engine_Break%2Din_%2D_Upgraded/m_1850473/tm.htm]this RCU thread[/link] describes and explains the break-in.

Two tanks are enough to make this engine usable and with a reasonable idle and transition.

Most engines I have run with the high-speed needle at 1.25-2.5 turns open.
3/8 of a turn open should be too closed, if anything; not too open.

The engine isn't meant to idle with the nose up.
It will never see this condition in flight (because it will be decelerating when you raise its nose in flight) and from the looks of it, this engine is not installed in a 3-D model as of yet. The idle should be adjusted in level attitude, to operate in a landing configuration and when going around.

A good starting position for the idle mixture, is with the air-bleed hole half-blocked by the adjustment screw. And back-out the idle-stop-screw enough, so you can shut the engine down with the throttle trim.

And the engine should die when you raise its nose on the ground...


Return the tank to center-line level = carburettor jet level and isolate it from all parts of the airframe with latex foam.

If the gasket below the carburettor is in one piece, any air sucked in is something you (and this engine) will have to live with.

I have the same engine as you.As Dar said idle should be on level not a raised position.My engine(inverted mounted) tends to leak from high speed needle so I have to put some fuel tubing to isolate(not so easy).I am using self mixed 80/20 full castor no nitro fuel.With OS 8 mine turns 11800 RPM with APC 10-6.High speed needle is about 2-2.5 turns(no nitro fuel).The engine is very reliable and never a deadstick.

Thank you both for your advise.

Think I was bringing the nose up/down a bit too high for the test.

The instruction manual says 15 deg's or so.

BTW, the engine will be installed into a Tower Hobbies Uproar 40.

Thanks again for the comments.

Dave

I just forgot to mention that, I removed the buffle inside the muffler(and recommend it too) and have an exhaust extension elbow.