Inverted engine starting, part 2

I'm surprised that no one has mentioned unintentional flooding while filling the tank. When the tank is full, there is usually some fuel forced forward into the venturi. If the crankshaft transfer port is open, this will flood the engine. You don't know why it won't start and its gonna take a lot of flipping to clear the engine. Many people will lose patience while flipping and add more prime to an already flooded engine. Of course you can always invert the airplane. Starting with the engine upright helps the excess fuel to drain and starts are generally easier from a flooded beginning. this is why I designed the Mustunt series to incorporate upright engines for beginners.

I think it is unnecessarily dangerous to flip the airplane, especially when the cause of flooding is so easy to prevent.

Always, when fueling, first turn the prop backward against compression to close the crankshaft transfer port. This should give you a dry engine to begin with. It will take a measured amount of prime/choking to start a cold engine. Usually, a few flips of choke is enough followed by slowly turning the engine over with the prop tightly held to feel the "bump". It is now ready to start. Hot engines frequently don't need priming/choking.

My airplanes are tightly cowled so choking is out of the question. Before fueling, I rotate the prop backward against compression to avoid flooding. To start a cold engine, after fueling, I rotate the prop forward against compression to open the crankshaft transfer port and use a small syringe/glue gun to squirt a small amount of fuel directly into the intake. Then rotate the engine to get a bump and the usual first flip start. If it fails to start in the first couple flips, I simply grab my starter. Typically, I get first flip starts. When the engine is warm, I never prime. It starts immediately or I grab the starter. For two stroke engines, I prefer not to use the starter as it is easier to just flip the prop and go. Maybe once in 20 starts, I will grab the starter if it doesn't start by hand flipping in the first two or three flips. In competition, you have a time limit for starting. I give the engine a couple of flips, then, if the engine doesn't start, grab the starter. I always start on the gear. I have never lost starting points.

I never start four stroke engines by hand, partly, because my smallest four stroke engine is a .72.

I strongly recommend starters to everyone. Having one nearby, in arms reach, seems to insure the engine will start promptly by flipping. I guess its presence intimidates my engines. In any case when I go to practice, I count of getting in a flight every 10 minutes. I always have charged start and starter batteries.

Some guys almost always get prompt hand starts and never buy a starter. At the World Championships in Liverpool in 1978, starters were not yet banned under FAI rules. Bob Geiseke couldn't get prompt starts in the cold, wet, English air. He asked to use my starter. He probably hasn't used one since, but when you need prompt starts it is a necessary backup.

First, It is necessary to understand how to avoid flooding the engine while filling the tank. Second, have a proper technique for priming/choking. Third, have a starter backup. It will seldom be necessary, but it does put an end to endless flipping.

It is altogether too easy to come up with solutions which are unique to particular situations. I usually fly by myself with a stooge. My Ro-Jett 76s never need prime for hot starts. The situation becomes more difficult when flying with a group of other flyers. When the engine is neither cold, which has a definite starting technique, or hot, needing no technique, it is sometimes difficult to guess just how much prime might be necessary. I tend toward little or no priming, usually start with a couple of flips, but keep the starter handy. I am much more likely to use a starter when flying with a group than when I'm by myself. Hot and cold starts are easy. Warm starts may be tricky unless you fly with others often enough to develop a warm engine technique.

Al, i use single vent tanks and fill by venting out through the feedpipe. I then add more fuel to the motor until it is flooded solid. This gives me a known base to begin my start-up proceedure. Any other system gives me an unknown amount of fuel in the engine. It works for me.

You miss my point. Without closing the crankshaft transfer port, any procedure for filling the tank may result in a flooded engine.

you missed MY point. I WANT it flooded!

>
>You miss my point. Without closing the crankshaft transfer
>port, any procedure for filling the tank may result in a
>flooded engine.
>
>Al

Al,
This is a non-issue in my program. I have never paid attention to where the crankshaft was oriented and I always enjoy first-time spinner flips - the only exception being in extremly cold conditions, like at the KOI. I cannot recall ever flooding my modern stunt models from fueling. If there is ever a problem starting on a first spinner flip, I typically need more prime.

I also see no need for an electric starter on my program.

Curt,

I get the spinner flips too. The way the venturi is setup on the PAs you cant flood it inverted. It poors out the venturi.

If I am using spraybar type needle like on my OS LA motors I have the hole in the NVA facing forward towards the front of the motor pretty much the same angle as my PA engines. I dont get floods on those motors either.

I use a Bru-line filter on all my ventuirs no matter what engine it is. It really helps the starting because the filter will hold the prime when you roll over the prop. Once I feel it is wet with my finger then I flip the motor through a few times with the venturi open. Then attach the battery, flip the spinner and off we go.

I must admit I don't understand this. If the engine's inverted then any fuel forced past the needle valve simply dribbles out onto the ground. Even when the tank is full any excess takes the easy path through the overflow. Am I missing something here?

If you have a thru spraybar venturi, and a single jet spraybar, if you pressurize the tank with the rotary valve open, it shoots a jet of fuel directly into the engine. Instant flood. My problem was with engines with hemi heads like Johnsons. Any fuel in the cyllinder is funneled directly into the plug.

LAST EDITED ON Jun-14-06 AT 02:04 AM (CST)
 
I'm with Brian (Yes! I do know who Downunder is! We had great times as rivals at Nationals and Queensland State Champs during the 70s.) I generally have the hole in the spraybar at the side rather than pointing into the intake. Also I just don't pump hard enough to get that jet going up into the crank hole thus into the case to flood the engine if it was pointing direct. Personal choice here Al and Phil. Sometimes through my own stupididity I have over choked on a cold day and flooded the old Merco engines.

The old 6-6-1 method almost always works for my ST60's. Yes, I back the prop up during fueling as Al does. But starting routine is just that, routine, and it seems to be different for most brand/style motors.

Some examples:

For all my ST 60's the routine is 6 fast flip chokes, 6 fast flips with no choke to atomize the fuels, attach the battery quickly then 1 fast finger tip spinner twist back against the compression. As long as the motor isn't stiff from sitting for months, it fires right up. If it doesn't, I also reach for the electric like Al.

My inverted Fox's take 3 fast flip chokes cold, 2 warm, who know's when hot, as many as you can stand before you burn that ring into your finger from the hot venturi, heh...

FP's and LA's all seem to flood easily, 2 chokes cold, 1 or none once they've run that day.

The Saito .56 in my Legacy takes one choke with my finger over the muffler, a couple of fast flips to atomize the fule, attach the battery and hit it with the electric. It starts very quick. I'd start it by hand, but it will run backwards sometimes, so I just stick with the electric.

The ROJett's spinner start like the ST60's, but need half the prime. They will loose their ability to spinner start after a while if I run fuel with too much castor oil over a period of time. A couple of tanks of mostly synthetic Powermaster RoJett blend and it's back to a nice squeek at the top and a finger tip spinner start every time.

Well, those are examples of one guys actual inverted starting routines, hope it helps.

Thanks guys. I have been wearing out my arm flipping, trying to get my Fox 35 (new) to start. Exhausted I thought I would come in and see if there was anything on the forum. From the above reading, most likely the poor thing is terminally flooded. It is on a test stand. What's the best(i.e. fastest) way to unflood it?

Don't force the engine to turn over if it's hydraulic locked, you could bend the con rod. Pull the glo plug out, invert the engine and back flip the fuel out. A note about test stands - The tank (assuming clunk tank) should not be much higher (maybe a tad, but not more than 1/2" higher) than the engine than as if you were installing it in a plane, otherwise it will constantly flood the engine on your stand without even priming it. Too low, and it may not want to draw fuel at all. If you have to, pinch or pull off the line until ready to start.

Have fun!
EricV

Weirdly, for me anyway, it depends on the engine. For example, the PA .40 Merlin I'm running is very consistent. Push the prop back as Al states to avoid flooding the engine to begin with. Fill the tank. Pull the prop through twice, holding a finger over the venturi (choke). Flip the prop twice, connect the battery and it will usually start on the first flip. (this is directly out of the instruction that Randy Smith supplies with the engine---and it works very well). Doesn't seem to much matter if the engine was run 5 minutes ago or a month ago. No prep, no burp, it just goes.

For the RO-Jett .65 I have, it's a little dicier. If I take the time to flip the plane over when it's cold and burp it a few time to clear the junk from the plug, then it's much the same as the steps above, though I usually have to choke it about a billion times to get enough fuel into it to start. It seems to be a very hard engine to flood. If not, then I can connect the battery for a bit and burn up the junk in the plug. Then choke and it will usually go, but it a lot more consistent and predictable if it's cleared first.

For the OS VF I've been learning to run, forget even trying to start it unless it's been cleared and burped a few times. The thing will be locked up from the last flight no matter what attitude the plane has been stored in. You have to put the plane tail down and mess with the prop for a few minutes to get the gunk to run back into the pipe, then flip it over and burp it two or three times. Then it's ready to go and starts pretty easily. Couple of chokes, flip the prop a couple of times, connect the battery and it starts on the first flip.

Cool thing about inverted 4s is if you should flood the motor you just roll the prop over a few times and it runs out he exhaust valve. But the starter usually takes care of all that anyway.