One more question. Now that i'm thinking the needle controls the flow of the fuel. Can it leave motre fuel than that you want to flow in your engine and stall while in midair? What do you mean by hydro lock? Hydro lock can occur only if excess fuel enters the engine.

And thatCline regulator, what is it? From the sound of it, it sounds like another needle for the fuel flow

Yes the needles control the amount of fuel that flows into the carb.

Yes a "too rich" setting will cause the engine to stall in the air. This is why tuning is so important.

Usually people set their engines properly on the ground, but forget that the engine will lean out in flight, so the engine cuts out and they do not know why.

You must run the engine slightly rich to prevent this.


Testing the engine nose up and nose down with 1/2 a tank helps to get the tuning right.

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Hydro lock

Fuel is not compressible.

Get too much fuel in the cylinder head, and the engine CANNOT turn over.

This is called Hydro lock.

If you force it you may break the crankshaft or piston rod... normally the latter.

Hydrolock can occur because of siphoning or user error... you over primed it.

You must drain the excess fuel out of the cylinder head when this happens.

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A cline regulator is used to maintain a constant pressure to the carb under most attitudes.

While normally not needed, it's a nice thing to have, particularly if your fuel tubing is long for any reason.

Short tubing runs increase available flow, so you are advised to keep your fuel tubes as short as possible ( with certain exceptions ).

i got an irvine 53 inverted in my bossanova, its fine but can be a real pain to start when its cold, usually you have to hold the plane upside down and prime it by hand (ignition off, finger over exhaust outlet, flick prop a few times) but after that its easy to start

First... if 1" of difference were all that important, how could we point our planes nose up? ( where there is MUCH more than a 1" difference ).

Second... how can you "detonate" a $300 engine because of siphoning? The only way I know of, involves utilizing explosives!

ANY engine ( even one properly set up ) can and will "hydro-lock" under some conditions.

It's up to the owner to recognize hydro-lock ( turning the engine over without the ignitor will tell you... ) and NOT use an electric starter when it happens.

That's it, nothing more required.

That one you said about fuel tube, that longer is not good. Why? I though that the longer the fuel tube is, then the best the flow you will have. For example, if the fuel tube is short and for a reason, the fuel tube in the tank catches bubbles and it doesn't anticipate to recover that air in the fuel tube and the engine will run lean and it will shut down.

I inverted my first motor last weekend. Tested it in the garage. GMS 76 with a remote wire for glow. I tested my recharchable glow igniter on a spare glow plug, would barely light up at all. Switched to wires off my field box set to 1.5 and it was bright red. with the regular glow igniter and starter, motor would flood. with the wires it fires up in a second. Have to use caution i believe, not too burn up plugs with the wires off the panel.

With good care of an engine, the glow plug last for a gallon and much more

No quite the opposite is true.

Try this...

Take a piece of new long tubing, say about 16 inches, and blow through it.

Now take a piece of new tubing say about 4 inches in length and try the same thing.

Big difference! It's rather amazing how much it changes.

Like running electricity down a length of wire, the longer the wire, the more resistance.... same with the fuel.

The short tube provides very little resistance to fuel flow.

Some people "loop" a piece of tubing around a tank to solve some attitude related problems.

However if you can avoid this, it is worth doing to make sure that pressure is consistent to the carb.

Keep your tubing as short as you can.


If you have a bubble problem fix that by other means... long tubing does not.

A Dubro "sintered" clunk helps a lot to get rid of bubbles... as does using an anti-vibration engine mount, and padding the fuel tank mount.

Click these:

[link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXD741&P=7]Dubro Clunk[/link]

[link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXXF25&P=ML]Bubbleless Clunk[/link]

You mean they burn out?

Just kidding...

If the engine is properly tuned they will last a long time... many seasons of flying.

Yeah but the coil inside the glow plug, after that long use will begin to deformed and eventually burn out, so it's good to replace the glow plus. They can change the performance too.

They only burn out if the the engine is run too lean.

There's a few guys here running with 10 year old glow plugs!

What can happen instead is that the coil will get coated with debris. This is usually the reason to change out the glow plug.

If the last two loops of your plug ( closest to the end ) do not light up then it may be time to replace it.

In a brand new glow plug's coil, the final loop doesn't light up anyway.

The very top 1/2 of the loop does not, but the loops below that should.

If the last 2 loops do not, it's time to change it out.

It (the cline) allows muffler (4S) or crankase(2S) pressure to build in the tank thru a one way valve in the pressure line and a fuel regulator which only allows fuel to flow to the carb as the engine demands. I have one in a zero with a tank 2 1/2 inches too high with an inverted 4S 90 engine and it works great. No fuel gets thru when filling and therefore no syphoning.