Please can anyone tell me if inverted engines are trouble or not i have put one in a
piper cub , i "ve been told that they are trouble ,can anyone give me advice please
Windowman

what size and type of motor is it

Hi:
Inverted engines can be difficult to start unless you follow a few basic steps. The problem comes from getting fuel into the glow plug and putting the fire out before you even get started! Most people have a helper hold the plane inverted when it gets really nasty.

Be sure that the tank is a bit on the low side so the fuel will not syphon into the carb. When fueling up clamp the line to the carb - or better yet fuel up using that line. Once fueled, do not prime or choke the engine. Use a starter and just crank it until the fuel flows in a normal fashion and it should fire up right away. A HOT glow driver is a must.

If all this fails, then get a buddy to hold the plane inverted.

If you follow these steps you should have no trouble and will have a clean installation.

Phil

The biggest problem with an inverted engine is taking off the glow starter once the engine is running . The second biggest problem is learning how to prime the engine because you're trying to get fuel to run uphill from the carb. This means that even if you let it sit so long it syphons all the fuel out of the tank then that fuel falls down onto the ground. All engines (upright or inverted) should be primed first before using the starter. The brute force method (grind it over until it fires) can work but I've seen an engine destroyed by using that method. Blocking the muffler outlet to force fuel from the tank is an acceptable compromise but then you have two hands close to the prop so be careful. If you overprime and flood the engine then you run the risk of damaging the conrod from a hydraulic lock.

I keep emphasising the prime because that's the only trick to it. Once you know what the engine needs then it's usually a one flick start every time. Or one bump from the starter.

Making sure the fuel tank is lowered at or below the carb line should be fine.

I've also found a glow plug with an "idle bar" can be helpful with inverted 2 strokes. An inverted 4 stroke is no sweat... just do it

I run os engines and 90% of my planes are a iverted engines they just need to be tuned to run inverted and have the fuel tank a little lower

HI Lannybob
thanks for the reply ,,its a 46 os engine,
keep on flying..
windowman

I found pretty much the same problems with my Excelleron 90 and it's inverted OS 1.20. You just can't get to the carb to choke it off to get fuel running, then once you do get it running, then you chance on loading the thing up with fuel. But, in this case, the OS 1.20 starts easy and runs well, so I probably figured out the best method of getting it started. One big thing is to make sure you keep the throttle closed all the way until you are ready to start the engine or you will find that your fuel will run all over the place.

Tank positioning becomes a problem... needs to be centered on the center line of the carb. Pain in the butt because many planes have you put the tank in a pre-determined spot which makes it tough to relocate (up or down).

I had an Evolution 100 in that plane when I first got it built. That engine was a nightmare to get started and keep running. It was so darned tempermental with tank position. That's when I invested in the OS 1.20 and most... most... of my troubles went away. It's still a bit of a pain but it does start and run much better than the 100 did.

To help alleviate the problem of the glow starter, consider putting in an on-board glow driver.

http://www2.towerhobbies.com/cgi-bin...&I=LXDZ82&P=ML

This is an example of what I am talking about. Not cheap at $42.00 but it will certainly do the job.

DS.

an o.s. 46 should run just fine inverted if tuned properly. what i do with mine is use a idle bar glow plug so not to quench the plug with excess oil and fuel and make sure your tank isnt higher than the carb. this will allow the fuel to syphon into the carb and allow more fuel into the motor than is required. if you cant lower your tank then put a loop in your fuel line leading to the carb. if it still doesnt run properly then try a glow driver. all of this in-which im telling you worked for me. glow driver is the last resort and sometimes required. let us know will ya.

CGRetired,

I have found that running a long fuel line from the tank to the carb and making sure it rises above the level of the top of the tank will help with siphon problems a bit. All of my glow suff is Saito, but I think most 4 strokes would behave in a similar fashion.

I know it won't help much, but it has allowed me to avoid some tuning problems and siphon issues. I flat-out refuse to run OBG or anything else that may add weight.

Just a side note, I guess.

(We now return you to your regularly sheduled thread, already in progress.)

Flooding is the most common problem with inverted engines and each installation will give different results.

I think the main reason for inverting an engine is to maintain a scale profile, no one wants a cylinder head sticking out the top of a cowl or a huge muffler hanging out the bottom.

If your inverted engine setup is prone to flooding, siphoning through the carb on its own, you can do two things.

1. Do not fuel up until your ready to fly.
2. Clamp off the carb feed line with a hemostat until your ready to fly.

As far as idle -bar glow plugs go, I've used all types and can see no difference, just use a good plug like a Enya #3, OS 7, or and number of quality plug, I've found the cheaper the plug the shorter it's life.

My inverted Super Tiger 90 powered World Spitfire has NO bad habits, no fueling problems.

My inverted MDS 148 powered World Funworld siphons, fuel drips out of the carb after fueling so I have to clamp the line.

I would just mount sideways and use the pitts muffler myself. This will put the exhaust straight down below the plane. Almost completly eliminates having any fuel spray to clean off the plane. You can also look at a slight downward angle mounting which will use your standard muffler and still put the exhaust below the plane. You may have to shave a part of the fuselage to make the muffler clear depending on the particular plane. Either method doesn't seem to bother the engine where as inverted running with a 2 stroke can be a real pain. [8D]

Am I reading this correctly that 4-strokes have less of a problem running inverted than 2-strokes?

If you are running an inverted engine and have it properly tuned, all you have to do is remember to close down the throttle to a high idle before you hit the engine with the starter.

That is; you prime the engine as usual at about 70% throttle, then drop the throttle to idle, connect the glow plug and start it.

Leaving the throttle wide open keeps the needle open allowing the fuel to siphon back fairly quickly even if you have your carb line correct... as most tail draggers point the nose up while on the ground...

Reducing the throttle permits this to happen far more slowly, potentially taking several minutes to occur and giving you ample time to start the engine.

4 strokes have their carb hanging down from the manifold when upright so any syphoning or massive overpriming just drips out. Invert the engine and then you can completely fill that manifold and the engine itself if the inlet valve is cracked open. Simply turning the engine backwards a couple of times will force the fuel out through the exhaust valve.

I never prime an inverted engine, either 4 or 2 stroke. It is so simple to just momentarily put your finger over the exhaust opening as you apply the starter. Before the starter makes more than two revolutions, the fuel is flowing properly and the engine usually starts right up (throttle set to high idle throughout procedure).

That makes me nervous because I'm getting ready to fire up my first Saito 100 on a Harrier 90, and the inlet seems to be about an inch below the fuel tank. Don't like the idea of detonating a $300 engine.

Pete,
Don't worry, you won't "detonate" anything.

Ken

If you're having trouble with your engine being inverted, just fly upside down all day long!

sorry Mboland i pressed a couple of wrong buttons thanks everyone
for the help on bicarb and my crashed cub
Windowman[&:]

sorry Mboland i pressed a couple of wrong buttons thanks everyone
for the help on bicarb and my crashed cub
Windowman[&:]

If the tank is higher than the fuel needle, and the plane is flying at midair, can the engine stall or something? And why set the throttle at high when you are going to start it? That definately stall the engine because the flow of the fuel into the carb will be many. My idea was set the throttle at full closed position, and then grab the starter. Attach it to the spinner, and when i'm ready, give a little throttle and start trying spin it. If it finally spinning, then i open the carb slowly slowly untill a safe point (with full throttle, the plane is going to fly ). Then, wait untill it starts and vouala. Another idea is to have your plane at inverted position when you are going to start the engine. How about that?

No.

The fuel tank height issue is overstated too often here.

It is suggested that the tank height be about the same as the carb needle height to prevent siphoning.

Siphoning is annoying and can also lead to hydro lock.

But the height does not affect engine performance.

Otherwise we would never be able to fly our planes with the nose pointed up or down...


No need what-so ever.

It's a good idea to open the throttle to prime the engine first, then bring the throttle back to idle.

If the tank height is not equal to the carb, then leaving the throttle at a high setting actually exacerbates the siphoning problem.

Fuel will flow back into the tank FASTER ( if the tank is lower ) or into the carb ( if the tank is higher ) causing starting problems.

Normally on the inverted engines I merely open the throttle, turn the engine over a few times while either holding my finger over the exhaust port or the carb intake ( to pull fuel in ), then bring the throttle back to idle ( so that the fuel does not flow back into the tank ), then quickly affix the ignitor and hit the spinner with the starter.

That's the only difference with an inverted mount!


Not needed at all.

If you feel you need to do that, either your engine is mistuned, you have fuel flow issues, or you are not doing things properly.

I run the majority of my engines inverted w/o any problems and I have a bunch of them this way.

Tank position, syphoning problems can be solved with a cline regulator.