How to get inverted 4 stroke to run.
 

All this engine needs is more breakin time and to be tuned correctly. The idle will get better as the engine breaks in. I would fly the plane instead of just setting on the ground. The extra cooling of the plane in flight is good for the engine and plus you get to enjoy it too. Do not expect perfection until you have burned couple of gallons of fuel through the engine. These engines take a couple of gallons to completely seat and the black residue is evidence of it.

How to get inverted 4 stroke to run.
 

No i don't have an OS. I fly Saito and that's it. I'll restate myself.....The Saito 1.00 was nearly borken in after 20 minutes of bench time. I've barely touched the needles and the gaps haven't needed adjusted. It will slowly continue to break in, but in no way should a enigne have over a gallon of fuel through it and "NOT" be broken in to the point where it won't run inverted.



Neo

How to get inverted 4 stroke to run.
 

Here's a new thought........running on the ground with cowling on or off? Could it possible be overheating. That would give off the dark exhaust residue that yor talking about.



Neo

How to get inverted 4 stroke to run.
 

Running slightly rich cools the plug down so the longer you run the wetter the plug gets until it finally blinks out!

Truth is said above about breakin. You should not attempt to run inverted until the motors broken in.
So put the motor on something else upright and fly it for a couple of gallons. Then come back and try again! Everyone here has made some very good points. Breakin, tank height .....etc. The only thing I WOULD NOT do is fly it. A triplane deadstick is just another name for a "pile O balsa!" And we wouldnt want that to happen.

How to get inverted 4 stroke to run.
 

Hi everyone.
I have a Saito 91 and an OS 120 Surpass 3 and they all run perfectly inverted. Great idle (about 2000 rpm or less on both) and they are still in the running in period.
I use on both OS type F plug and the fuel is 18% Klotz super techniplate oil and 10% modeltechnics nitro.
They also start great without any problems.

How to get inverted 4 stroke to run.
 

Well now I can get just under two minutes. Actually if I adjust it for a perfect transition I can only get about 45 seconds, if I adjust it so lean it quits when i go full throttle it will idle longer than I care to wait on. I settled for a slight hesitation to full throttle and it would idle from a minute 45 seconds to over two minutes. In fact I flew the plane for the first time. Flew it twice, on the third time the idle acted up again and after I took the cowl off I noticed some Monocote lifting off around the cowl so I put it away for the day. Fun plane to fly. I thought taxing without a tail-wheel would be more difficult but it wasn't. Both landings were long. I kept thinking the plane would fall out of the sky but instead it floated to the end of the runway. Course If I had it idling below 2800 would help. The first landing was long but a perfect touchdown. The I used the wing tip skids on the second one! With that narrow landing gear and top heavy with wings It doesn't take much to dip a wing tip. Wants to snap on the second loop, very small loops if using full elevator, I will reduce elevator travel for the next flight. Easy plane to takeoff, with hardly any up elevator it will climb steep and slow.

I am thinking maybe the manufacture put an extra head gasket in the engine? With 10% fuel you get an RPM drop off even with OS F or ThunderBolt plug, no matter how lean you set it. Not so with 15%, unless inverted. I'm going to check on this tonight, if there is no second gasket I'm gonna buy an on board glow igniter.

How to get inverted 4 stroke to run.
 

Nix that, I stripped the head of the screw holding the rocker cradel, I didn't check the allen wrench that was rounded.

Also noticed that the midrange is rich, bet if I lower the tank the midrange will lean out a bit and allow a transition from a leaner idle setting. I know this is what some recommended from the beginning, but the engine just wouldn't idle for any length of time at any mixture setting. Now that it has broken in some and would idle continously at a lean idle, and the midrange seems rich while flying, but lean inverted, I think lowering the tank is in order. I'm going to try shaving some wood off the former that holds the tank and tilt the back end of the tank down some more for starters.

How to get inverted 4 stroke to run.
 

I have read where others claim its the tank location, well not sure about that as I have a Satio 100 inverted on the WM SSS, the tank center line is 1" higher then the carburetor and it idles just fine. I voted its all in the settings although it was ran on an AW Edge mounted sideways, for a good two seasons.

I have a good friend that is a master mechanic which has taken me under his wing and is showing me the ropes, things to look for and how the mixture works.

The Saito low end is very, very picky all it needs is just a touch in order to make a difference in your idle.

Blackie

How to get inverted 4 stroke to run.
 

My Saito 56 is mounted inverted. It starts and runs as well as any upright engine. It is very reliable.

BUT, I had to reposition the tank in the model.

The plan had it higher. (upright engine in the plan) The inverted engine mounting altered the carby height in relation to the tank.

So I lowered the tank about 5/8 of an inch. No problems.

Upside down Saito
 

I'm running a Saito .30 inverted in a ModelTech Cub, Fox Miracle Plug, WildCat 15% premium and a 10x5 or 9x7 depending on the grass length.

How to get inverted 4 stroke to run.
 

Thats nice about the engines you are running inverted, but I don't know how that helps?

Basic
 

It's basic and simple, I merely explained what works.

How to get inverted 4 stroke to run.
 

And at least four people have said that their TT .91's work inverted also. At least one in the same ARF. So what? Doesn't tell me why this engine doesn't work.

Safe saying
 

If it was a Saito I'd feel very safe in saying the low speed needle is still rich but very close or that you're trying to get it to idle too slow. A TT should be the same.

How to get inverted 4 stroke to run.
 

When I flew it the idle was 2,800 which is too fast for landings. It will now idle more than I care to wait on if I lean it enough. It wouldn't do that before. But rich enough for a good transition and it will only idle for about 45 seconds. Hopefully lowering the back of the tank another 1/2 inch will do the trick.

How to get inverted 4 stroke to run.
 

Sport_Pilot, have you tried seeing what your engine would do on a test stand, inverted? the reason I ask, is that I wonder if its your throttle servo not transiting properly? I have this problem on mine and plan to swap out my Hitec standard 422 for a more reliable servo.


Blackie

How to get inverted 4 stroke to run.
 

Yes and same thing, though I couldn't time it.

RE: How to get inverted 4 stroke to run.
 

in my experience with OS FS-52 Heli engine on a Nexus helicopter, inverted 120 degrees.
not 90 or 180.
I had a lot of trouble at first, try using different plugs etc.
but it seems that FS don't like castor when inverted.
once I changed to 100% synthetic lube fuel, everything was well.

also, for some reason synthetic was able to remove brown black varnish that built up on engine
and muffler by castor residue.

RE: How to get inverted 4 stroke to run.
 

Actually switching to Coolpower helped a lot. I was getting reliable flights before I crashed the DR-1. About a dozen reliable flights. It never idleded as low as I wanted. The three most helpfull things in order of most to least helpfull was more run time, getting a plug that was hotter than OS-F, and switching to an all synthetic fuel. Still I got more revs with a cooler plug but could not get a low idle with them. I may add a simple home made on board glow with a micro switch when I rebuild the model.