Can anyone tell me if I install an engine in an aircraft upside down on the mount would I have any problems with it running correct? The engine is an OS .61.
Thanks

Inverted engines are very common. Some installations can have problems with flooding if the tank is mounted too high but it is otherwise no big deal.

It all depends if it is a 2 stroke or a 4 stroke. I have an OS .61 4 st and it runs very well inverted. Whereas, any 2 stroke that I put in inverted ran like crap. I only install my 2 strokes horizontal or upright now and they all run great.

Where I live every engine is upside down by most of the world. Running an engine inverted is no problem as long as you still setup the aircraft correctly, Tank height, fuel lines ect. Just remember that with an engine inverted it will flood easy if you over prime.

Cheers

2 strokers, 4 strokers, they both run upside down just fine.

Those who think not, have not eliminated the "other" problems they are having first.

Almost all of my planes have inverted engines, and it is no more difficult to set up and tune an inverted mount engine than it is to deal with an upright or side mount engine.

2 st and 4 st may run the same inverted but that is the trick, to get the 2 st started without flooding. When inverted, the fuel has a tendancie to pool on the glow plug in a 2 st making it hard to start. Whereas, a 4 strokes' glow plug is on an angle so fuel has little chance of pooling thus making a 4 st a better inverted choice.. That being said, it is also more difficult to install and remove your glow ignitor from an inverted 2 st so a remote glow ignitor may have to be installed. Tank height will also be very imortant. In a lot of 40 size planes it may be very difficult to get the tank down low enough when trying to invert a 2 st. Another viable install option for an inverted 2st, is to install it about 5-10 degrees tilted to one side as this will greatly decrease the chance of fuel pooling on the glow plug and make starts easier. Like I stated earlier, I prefer a horizontal or upright 2 st for simplicity and less fuss. Each to their own!!!!!

Curt

I use a fuel filler valve for inverted applications. I just leave the connector plugged in the filler valve until I,m ready to start the engine. Radio on, plane on, glow on, pull fuel fitting and start. After I land and taxi in I shut down engine and plug filler in to keep fuel from flooding carb.

Eh, with all due respect...

A properly tuned idle will help eliminate or reduce siphoning caused by tank height differences to almost nil. At idle the siphoning flow should drop to a very slow drip which is not problematic.

The tank height is not as crucial as made out to be, while it helps to eliminate siphoning in either direction, on a normal arf flipping the engine inverted will produce almost no difference in runs... even if the tank is left as designed. Quite often this is overstated here as a problem, when it is not. We would all have nothing but deadsticks the second we point our engines nose up in flight... if tank height was as problematic as it is made out to be.

As far as starting, an inverted 2 stroker may only need a bit less or more priming and it is advisable to run the engine up for 10-20 seconds when it is cold to help bring up the head temperature.

As far as pooling, you are advised to use a "long" plug on inverted engines to keep the element out of any fuel in case it occurs. This is something not often tried by those who are having problems with inverted mount engines.

If ignitor clearance is an issue inverted then it is usually an issue upright as well, however I've seen people become very apprehensive about reaching down to grab an ignitor...

I've no problem with this, but as said to each their own... in this case a remote ignitor is easy to install and use, and it brings your hands safely away from the spinning prop, much more so than an upright or side mount engine.

I've never had to resort to any measures to keep the carb from flooding on inverted mounts, and I've never had to change the position of a tank to get an engine to run or idle properly.

I have seen people complain about an inverted engine which they could not get running... especially when the engine is new...

I change out their plug for a long one, and get them to put on a slightly heavier APC prop during break-in... I then show them how to start their engine... no problems thereafter.

Thanks moto x,that was the missing link for me re starting/priming an engine consistently after i took it off the test bench and installed it upside down in my decathlon.Thank you mate

Heavy props are good on fourstrokes

cheers guys

set them up right and tune them they run perfect

For that engine........
Depends on where the tank is in relationship to the carb, and how wild you fly.

Most times, the decision is based simply on where the carb lines up with the fuel tank. However, it also depends on the engine itself. Some of the 4strokes really get out of sorts when inverted. I watched one of our 4stroke fanboys "wreck" one of his best a few weeks back. And I've sent back and had replaced a design that didn't work inverted with the first and it's replacement. I'm told it had to be something with the plane. But when I stuck in a two stroke it worked excellently. And had same carb orientation. So it wasn't the plane.

Re: Carb relationship...

Invert the engine and you tend to IMPROVE the carb/tank line on most tail draggers.

Tail draggers tend to sit nose high.

By inverting the engine you tend to lower the carb.

With the nose high attitude, the tank height is more in line with the carb, at least while the plane is at rest.

Of course there are exceptions....


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NOT that the tank height relationship has all that much impact on the running and starting of an engine...

blackhack

For what it's worth, this is how I treat my "inverted engine" applications. I invert the whole airplane, and rest it in a cradle built for the plane. I usually have to do this anyway in order to bolt the wing on. Then I start the engine while the plane is still inverted (engine is now right way up). Easy to put glow starter on and off. After enging is running, I flip plane over, and off I go. After my flight, I again rest the plane upside down in it's cradle until I am ready for the next flight.

Lm

For what it's worth, I now mount my (2 stroke) engines at 135* angle, so the muffler comes out the bottom center of the plane, and the engine is not fully inverted which eliminates any hardship of a soaked plug trying to glow. Works well and looks great.

You are welcome Old Fart.