kmiller

Hello everyone.... I am almost a complete rookie when it comes to the sport of RC flying (started last summer) and am looking for a bit of help here with my first 4 stroke engine.

I just purchased a saito 72 for my great planes Zlin and have it mounted inverted as per the instructions. I have run a couple tanks through the engine and got the tuning done (running at about 10200 rpm down from the 10600 peak) and have dialed in the low end needle as well. Once I get it running it purrs like a kitten. The issue I am having is starting it reliably. Ihave found that priming it the way I did my evolution trainer (thumb over the exhaust to prime) results in the engine flooding and fouling the plug. After taking out the plug, and usually replacing it, the engine seems to start nicely with the electric starter if Ihave the plane upside down (resulting in the engine being upright). What is the proper proceedure for starting this engine inverted WITHOUThaving to go through the trouble of pulling out the plug etc as it is a pain due to the configureation of this plane. Can someone also explain the backflick method of starting these engines as well.

Thanks in advance!

...happy flying

SrTelemaster150

Use an electric starter. Have your throttle trim set so that it kills the engine by closing the throttle completely.

Get the engine spinning W/the throttle & trim closed, then open the throttle slowly W/the throttle trim until the engine draws fuel & lights off.

ThumbSkull

My Feedback: (57)

Yep. Prime not necessary. Keep the throttle closed at all times till you get the starter on it. Keeping the throttle closed will keep the fuel from flowing through the carb and filling the intake tube with fuel while it sits.

gerryndennis

Yeah if you are using a starter you don't need to prime, but it will start quicker if correctly primed first.

Don't know how you apply the starter with the throttle closed then slowly open it. Must be a three handed job.

This is my method for priming inverted engines. Throttle wide. Block carb with finger or choke and pull through six to eight compressions (eight to ten if you block the muffler instead). Note pull through not flick. You should feel the engine getting juicy and starting to free up a bit. (The number of compressions may vary due to length of fuel line to carb etc, you may need more or less).

Now vigorously flick the prop half a dozen times or so, this will check that the engine isn't hydraulic locked and distribute the mixture into the cylinder. If you feel resistance to flicking rotate the engine backwards a few revolutions to push the excess fuel out the exhaust valve then do the half dozen flicks. Your engine should now start at the first bump of the starter or after one or two back flips. (You may need to cross your fingers or stick your tongue out as well)

Here's how I do the back flick. The aim is to bounce it off compression not flick it over compression ie rotate, let go, then it hits compression and fires. It's easier with a spinner fitted but can be done without. The prop needs to be fitted at the normal 10 past 8 position or maybe a bit closer to 1/4 past 9 coming up on compression.

First prime as above then set the throttle to a fast idle. Rotate the prop backward to you feel compression. The blades should now be at 5 past 6 or 10 past 7. Turn on the glow. Turn the prop forward just over 1/4 of a turn till the blades are horizontal. Grip the spinner (right hand) with your thumb at about the 7 o'clock position and your first and index fingers at about 2 to 3 or resting on the leading edge of the prop close to the hub. Give the spinner a quick flick clockwise (rotating the engine backwards) from the wrist. You will find that your hand automatically releases and drops clear as the blade goes through the 6 o'clock position, the engine will come up against compression shortly after and hopefully fire, and bounce off compression in the correct running direction.

If the engine bounces twice and starts backwards try reducing the amount of prime or close the throttle a bit

I consider this method of starting to be safer than flicking forward over compression or using a starter (I've seen both methods go badly wrong). With the back flip method if your fingers are slow to come out of the prop arc they will be relatively gently pushed out of the way by the blunt leading edge of the prop close to the hub turning slowly. A much better proposition than being whacked by the blade at speed halfway out the blade, or having the engine backfire causing the trailing edge to cut to the bone. Or having the starter cone slip of the spinner launching your hand and starter into the now running propellor. I know you always use a chicken stick but I've seen them cause props to break or get flung a fair distance after a backfire as well.

Like everything its a technique that needs practice, try it without glow till you are happy.

It's easier and quicker than reading this post.

This method works best with larger engines due to the higher inertia but I find starting engines both two and four stroke down to .40 size no problem. Your mileage may vary, filmed under controlled conditions by professionals, do not try this at home, if you break something or hurt yourself you did it wrong and it wasn't my fault.

Good luck

Dave H

Rudolph Hart

Hi km just store your fuse upside down between times so the oil does'nt seep past the ring and dribble all over your plug.When you get to the field and put the plane together don't muck about,put the glo stick on and give it a flick backwards,easy as mate

kmiller

Thanks for the insight.....  Guess I will just have to try each method and see what works best for me.

SrTelemaster150

If you have an electric starter use it, at least for the initial start of the day.

I use a 90 sized starter to start 4-stroke engines up to 3.00 cubic inches.

Closing the throttle allows easy turn-over W/O hydrolock or kickback.

You can start the engine this way long before you ever get a prime into the manifold the other way.

After fueling, just hook up the glow driver, close the throttle, get her spinning & open the throttle W/the trim.

Viola', you engine is running.

kmiller

Sr, for the benefit of all of us can you please explain how you manage to hold the plane, the starter AND adjust the trim at the same time.  Your method sounds very logical, simply and safe..... except for the three handed bit.

Much appreciated!

Rudolph Hart

What?? you did'nt know his nickname is okky?

Altered1

The most important bit here!

SrTelemaster150

I push 2 landscape spikes into the ground behind the front maingear axles.

You can also make some small wheel chocks.

My start-up ground equipment consistes of 3 landscape splkes.

2 for the maingear, 1 has a length of nylon sash cord that I loop around the tail to stop forward motion.

Rudolph Hart

You're prop must start backwords,or you;re the bravest person i know.

ThumbSkull

My Feedback: (57)

It's pretty simple fellas. Keep the throttle close till its time to apply the starter. Glow on.
Trim throttle up. Give it about 10% on the stick the hit it with the starter.

SrTelemaster150

What are you talking about?

The plane is tetered at the tail via the sash cord so it can't lunge forward. 3 spikes. 1 secures the tail W/a cord, 2 go in behind the manigear to prevent backward movement.

How is that more dangerous than holding the fuselage directly behind the prop while you apply the starter?

bandit357

i run both a Saito .19 and a Magnum .91, each starts just a little different, the saito takes 2 revolutions of priming plugging the muffler, and the Magnum takes 3 rev's. yes my magnum is inverted, soooo, i have a fuel shut off on the fuel line so fuel doesn't flow into the engine when not running ( learned that one early). Now the neat part, i start both engines ( and even a Saito 100 twin) by turning backwards against the compression, and they start every time, really slick.. i know it doesn't make sense, but it works every time with out fail. just darn cool. so turn counter clockwise to prime, turn clockwise to start.. try it.

By the way, i dont even own an electric starter, never use them. ( i learned way back in the old days when the 4 strokes first came out)

Rudolph Hart

I was talking about prop strikes any size.My point was that ego's can hurt you and a helper is good insurance when you fire the engine up.

SrTelemaster150

Yes of course, but sometimes I'm the only one there.

Then it help to have a plan. I always try to have the things neccessary to fly if I'm at the field alone.

This also comes into play when tuning. etc, at home.

landeck

My Feedback: (1)

About 30 years ago I cut my hand badly in the prop while out at the field. If I had been there alone I would have been up the creek without a paddle. Since then I never fly alone![]

Bruce

Rodney

Most all of my engines, 2 and 4 stroke, once warmed up usually start with a quick backward (clockwise) flip of the spinner; it backfires and starts right up. Just grasp the spinner between thumb and fore finger and give a sharp clockwise flip.

SrTelemaster150

Life is full of risks.

I can't see any injury that might occur at the flying field that would prevent me from seekinh help.

Then of course I might get struck by lightening.

1QwkSport2.5r

I start my engines cold like this, although a warm engine needs less prime to backflip start. Inverted is a totally different ball of wax though. An engine should run as well right side up as upside down. Getting it started can be the tricky part. I use a starter on inverted engines without question. I like easy.

SrTelemaster150

The only issue W/inverted is the tendency to hydrolock as fuel runs into the engine instead of out of the breather when flooded.

All of my Saitos are running on CDI so once they are warmed up it is a simple matter of turning on the ignition & flipping the prop through (not backwards like on GI) W/the throttle just above idle.

On the 1st start of the day I use the starter as described on all of my engine up to & including the 300 twin..

1QwkSport2.5r

I've really only ever gotten wet glow plugs out of the deal, never a hydro-lock. Or hydraulic lock for the persnickety.

SrTelemaster150

Wet glow plugs?

What are those?

1QwkSport2.5r

Not all of us are as passionate about CDI ignition as you are. I think the vast majority of us run glow ignition, so assuming the OP is using glow ignition, my comment was pertinent.