So, my profile technique works fine on my LA 46:  When cold, hold a thumb over the venturi, pull it through four or five times, remove thumb, pull it through five times, rotate prop backwards against compression, connect glow, strike the prop.  Pretty much starts first flip every time.

However, given that I am using a stooge, what's a good technique for starting an engine that is inverted?

thanks,

Peter

Thanks for the tips, Dan.  Much appreciate that you can be counted on to offer advice.

Yes, the "fuel falling out of the venturi" thing took a little while to figure out; it was mildly alarming.  My experience so far is that there is more of a tendency to flood and a greater demand on the glow battery.  Eventually, I'll probably figure it out, and hope to avoid going to an electric starter.  Had a Nobler circa 1975, but that was 45 years ago and before mufflers, right?

Peter

Thanks for the tips, Dan.  Much appreciate that you can be counted on to offer advice.

Yes, the "fuel falling out of the venturi" thing took a little while to figure out; it was mildly alarming.  My experience so far is that there is more of a tendency to flood and a greater demand on the glow battery.  Eventually, I'll probably figure it out, and hope to avoid going to an electric starter.  Had a Nobler circa 1975, but that was 45 years ago and before mufflers, right?

   There is nearly *no* tendency to flood with an inverted engine, it's nearly impossible, unless you just grossly overchoke it and get it hydraulically locked. The crankcase simply can't fill up with fuel. Even if you do get a lock, back-bumping it causes the excess to spit out the venturi.

  Here is my recommendation (from another thread):

   Once it is burped, if the engine has cooled from the last run, fill tank, pull through with finger over the intake 3-4 times (choking) , then remove finger and flip through forwards immediately, about 5-6 times (aerate). Hold on to prop to attach the battery. Once the batter is connected and the helper is holding, bump the engine up against compression backwards, should start right off. Try a few more times. If you get nothing, no pops, then hold prop, remove battery, repeat choke procedure, repeat aeration procedure, hold prop, attach battery, back-bump.

    If it is still hot, fill tank, pull through compression once or twice, aerate, hold prop, attach battery, bump backwards. My PA61 and most PAs need at most one choke when hot, and 3-4 when cold.

    Note that back-bumping is not flipping it backwards through compression, you never flip it through compression in either direction, unless you have some spare fingers. Just turn it CCW until it starts to come up on compression, then fling it backwards up against compression in the CW direction. Don't use a chicken stick or anything like that. If you are doing it correctly, your fingers are not on the prop or spinner when it pops.

    You have to experiment to know how much to choke under different conditions. Usually, you can tell by the sound it makes when you are aerating it. It should sound slightly juicy, more than it you were going to flip it through forward. Any excess will be blown out. It will take much more choking when the engine is cold than when it is hot. If the engine is in an intermediate state, it may be very difficult to start because you have to choke it, and the cold fuel will get on the underside of the piston and shrink it, and leave the sleeve hot, so the compression will sort of go away. If this happens, aerate many times until you feel the compression start to come back.

     NEVER attach the battery without holding the prop, and NEVER flip it with fuel in it unless someone it holding it. The engine can start without the battery pretty easily, once you get the perfect mixture. It can also start spontaneously when you attach the battery. These are extremely powerful engines with very strong razor-sharp propellors, and have such good piston fits that they can start in conditions when you do not expect, once it is choked and aerated properly.

     The issue that many people have with this is in bold above - they remove their finger after choking and wait, then try to aerate the charge. As soon as you get the last choke done, you have to remove your finger and flip *immediately*, like, right then, as your finger is coming off. Otherwise your gas will run out on the ground and none will get in the cylinder. When that fails, they assume they didn't choke it enough, and do it more. Eventually, they choke so much that it fills up the venturi, and spills the excess into the engine, where it locks it up.

   The other problem is that people do not understand what "back-bumping" means. You never, ever, under any circumstances, *flip it through compression backwards* Run it forward up onto compression, attach the battery (*while holding the prop*), then just fling it backwards so it coasts freely onto compression backwards. Your finger should be off the prop long before the engine comes up on compression. You don't have to whack it like you are chopping wood, but briskly fling it. Once you know what you are doing, you can just lightly twist the spinner to get it moving, and it will start.

  This is vastly safer than attempting to start it by flipping forwards through compression like they did it in 1948, because you finger is off the prop when it could possibly fire. This wasn't that big a deal with a Fox 35 and a beechwood prop, it could whack you and it would hurt, but not likely to lop off any parts. Jett 61 with a carbon-fiber 3-blade, it certainly can, easily, and not even slow down.

     Brett

   Jim is correct, and I forgot to mention it. The engine is a pump, sort of, and can pull fuel in when the piston is going up and creating vacuum in the crank case. When the piston is going down, and you have your finger over the venturi, it can push all the fuel in the line that you just pulled up and puch  it back in the tank. On your profile models, watch the fuel line as you choke it slowly, you'll see the fuel flow both ways. Physics in action!
   Type at you later,
    Dan McEntee

How would the spray bottle be used for an inverted start?

      If you have a muffler on the engine, and any kind of filter or panty hose on the venturi, it can't.
   Type at you later,
  Dan McEntee