Thanks guys, mabey i should just try to get it running the way it is. In the World Models Groovy 50 3A, which is what the fl is in, the fuel tank is kind of fixed. You can't move it anywhere else than where it is. Last time I looked the centerline looked pretty close to perferct. What do you guys think the stock setting for the airbleed carb is, any tips for tunning it? Imagine starting from scratch and you have no idea where the stock setting is. I am going to give it one last tunning attempt tomorrow.

Inverted 4 cycles are the most difficult and dangerous to start. The fuel can collect at the bottom of the cyclinder near the plug and cause a hydraulic lock. That is why full sized radials are always pulled through at least 4 times to make sure oil or gas hasn't collected in the inverted cylinders. Suppose the cylinder is flooded as the piston starts into the compression stroke? Both valves are closed and when you hit it with an electric starter, POW one bent connecting rod or busted wrist pin.

When right side up, a flood is easily cleared by turning the engine backwards.

As Jimnie mentioned, it's a sad fact that some ARF's are designed for an inverted engine and the fuel tank is in the wrong place. There's not much you can do except re-build the whole front end, which cancels out the reason a person buys an ARF in the first place. How bad does the center line of the tank offset the carb spraybar on your plane Cambo? Anyway, a good starting point for the idle adjustment on an air-bleed is to adjust the needle until the air orfice is half way closed by the needle. If it was mine, I'd be tempted to cut a hole in the cowl and flip the engine over.

Another easier way to solve the inverted engine problem is to use a Perry oscillating pump. It only supplies the amount of fuel the engine needs. It operates on the reaction of the torque caused by the firing of the engine. As the engine oscillates back and forth the pump supplies fuel. I used one on my Goldberg Cub. Had a saito 50 mounted inverted and with the tank mounted high tended to flood at low rpm or just sitting when the tank was full.

Well, i just looked at the center line, i would gues that the fuel tank is about 1/4 to 1/2 of an inch higher. I never thought of a pump but that seems like it would add alot of weight? Mabey not though. What if i tried to tune the engine while the plane was inverted on a stand, would this help.
Now that it think of it, last time i tried tunning the engine, it would always quit at idle, even if the air bleed whole was wide open.

Hey, what if i mounted it sideways? Is there a pitts muffler for this engine? Would that help?

Cambo, the tank is probably close enough. I'd start with the air bleed hole half closed and go from there. The Perry oscillating pump doesn't weigh much at all. It's just a little work to install, and adds another factor in the tuning equation.

Will a pump or a onboard glow starter work better?

Where could i get a pump?

Cambo, I've solved this problem before with a Cline Regulator, but they are kind of expensive. Try fixing it by tuning again.

If the engine runs better when the plug is being heated that means one thing, the idle is too rich. When the mixture is too rich the plug element gets cooled by the overly juicy mix and the rpm's drop giving you the symptoms you have. That could be because of a badly located fuel tank or any number of things already mentioned but why don't you just try leaning out the idle screw. If it is a true air bleed carb turning the needle counter clockwise will lean it out. Try a quarter turn at a time untill you get it close, then fine tune it. When it is right there should be no difference between having the glow plug hooked up or not.

Good Luck

Actually the Perry Micro oscillating pump almost never needs any kind of adjustment other than the factory setting. I have 6 of them and have used them on a dozen airplanes. NEVER had to change the factory setting. Used from an OS FS20 up to an OS120 surpass that had a bad pump. All worked fine. I use them whether I have fuel problems or not.

Yessssssssssssssssssssssssssssssssss! It runs! I was using way to powerful fuel, 30%. The plane will finally not move at idle. I was using that fuel for a high altitude airfield. Well, the plane got moved to a lower altitude.
Just wondering, how do you now if the engine is running to lean. If the engine runs at idle for 1-2 minutes and slowly sputters and quites, is the idle two lean or to rich?

Locate the tank correctly, and forget about the extra junk. I personally have had 4 planes with inverted 4 strokes, and not 1 problem when set up correctly.

On setting the idle mixture, it could be either way. You will have to do the pinch test and/or move the needle around some to find out.

Enjoy,

Jim

If the idle is better with onboard ignition being too rich isn't the only cause. Low Nitro methane and a too cold plug will cause the same symptoms. In a 4 stroke, you want the hottest plug available. I use either the OC type F or the Enya #3. Actually I use the Enya in all of my glow engines. To quickly check the idle mixture, pinch off the fuel line while idling. If the engine speeds up it is too rich. If it dies quickly it's too lean. Very simple check. Another giveaway that you are using a too cold plug or too low nitro is if the engine slows considerably when you remove your glowdriver after starting.

If you want it to send smoke signals and waste a lot of fuel that is.

Is that why OS recommends the Type F plug and Enya recommends their #3 and everybody else makes a four cycle plug which is at the very high end of the heat range?? You need a hot plug to keeps things going during the exhaust stroke. Get a copy of C. Lee's books on the 4 cycle engine or any of the other engine gurus and look at what they say.

Those plugs are best with low nitro, 10% and lower. For high nitro that is 20% and greater the K&B 4C often works the best. No idleing problems either. If you like hot plugs try the Thunderbolt four cycle plug. IMO too hot for anything other than FAI fuel and inverted engines. But will make lots of smoke and burn lots of fuel. But power will be off.

You better tell that to my YS's. They all run on YS20/20 fuel. I use Enya #3's in them and they run just fine. No smoke and no excess fuel consumption. 20/20 is 20% nitro and 20% oil.

YS with their pressure boost may be an exception. But have you tried plugs such as the Fox Miricle and K&B 4C? A colder plug may give more power and less fuel consumption. However lack of smoke is an indication that you are at least close.

You said the hotter the better, so why are you using a non fourstroke plug that is cooler than the OS F? And much cooler than the Thunderbolt 4C.

I have been running 4 cycle engines since they first came out and still have all 5 versions of the original OSFS60 including the very first one with the machined heads and rockers. Been using them since 1977. I know what works and what doesn't and have tried about every combination you can think of. Tried all the "claimed" 4 cycle plugs as they came out. There are only two I use. the Enya #3 and the OS type F. You say the Enya is a two Cycle plug?? Then why is it that Every Enya 4 cycle comes with one and Enya recommends them? Enya makes a #3,4,5,and 6 and they get colder as the number increases. The #3 runs the best of all and the cold plugs will not idle. I run the three in just about every glow engine I have. By definition if the same engine is using more fuel it is generating more power.

Saito 45 with an enya #3, HShack white lightning fuel and Zinger 11x6 prop. Pilot Sky Loop 404 with a 6 ounce tank. Will run over 25 minutes. I wouldn't call that excessive fuel consumption.

At least close?? I'm right on.

Basically yes. It may run in Enya's and YS, but I could not get it to idle well on an OS .91FS. I could get it to idle but not well. The OS .91FS ran about as well on an A3, which I have tried in a pinch, runs but you have to settle for a higer idle speed. I think the Enya is a bit better though. Compare that to the K&B 4C which is obviously colder but idles well.

An A3 is not suggested in a 4str. engine.
Only *4str.* glowplugs like #F.
You need some tuning friend![8D]

Well maybe its because I can tune an engine that I was able to make it work. Or maybe because any real hot plug will run in a four stroke. But a four stroke plug is better because it will be hotter at idle, without being as hot at full speed.