Well put John and point taken. I'll get someone at the field to help me lower it.

Food for thought! A 2 St engine inverted can not hydro lock unless you are trying to start it or it has been run rich and let set! The carb. points down and fuel will not run up into the crank. A 4 St. will because the carb points Up and the fuel fills the valve port and into the cylinder.
Larry K

DON'T LEAN IT. You will fry bearings. You need to fix the tank height. Don't just assume the designers know what they are doing. The tunnel under the nose is for a rear exhaust tuned pipe engine. The only 2 engines I found with rear exhaust are 140's witch gos ageist GP recommendations not to over power the plane.


Plan A: Cut the tunnel out and make a hatch then adjust the height of the tank using foam on the top and bottom of the tank.
Plan B: Perry Regulating pump, or stand alone regulator.
Plan C: Grab an OS or YS pumped engine.

Live wires point is correct and I mistated however if the system is syponing to the carb on the two stroke it will lock when you hit it with a starter.

Another situation that occurs with a two stroke thats inverted and that is when the airplane is picked up after a flight to return to the pits or for transport the combustion gunk that collects in a factory type twostroke muffler will if picked up nose low and the prop is in the right position will run back into the chamber causing another form of hydro lock if it is not checked first.

John

In my experience (aside from whatever starting issues that may go with an inverted engine), tank location r/e the carb DOES make a difference. I own a U-Can-Do .46, with an OS 70 - mounted sideways, not inverted. This has been a great combination - with a very trouble free running engine. It was used when I purchased it.

Of the points raised before: yes - a non-broken-in engine can be troublesome, at first. Some of the Chinese engines tend to have harder cylinders and / or rings, and take a longer time to break in (vs. an OS, for instance).

As to the tank location: in the short term, it doesn't matter - i.e. you can fly your airplane upside down, climb vertically, etc., it'll still run. BUT - over a 7 - 10 minute run, tank location does. Try holding your airplane running nose down, idling, for several minutes. You will notice a difference.

Running lean will not hurt the bearings. It can hurt the liner, but not the bearings. Engines do seem to be more sensitive to idle adjustments when inverted, I suppose due to the fuel tank height issue we've been talking about. Keep leaning the idle until it runs and transitions right, which will likely mean the LSN will be turned in a little more than it would be in an inverted setup due to the fuel pressure difference. Because the right setting is farther in, the needle becomes more sensitive which can mean that the difference between just right and too lean is very small. So when you're close, make tiny adjustments until it's exactly right.

Idle bar glow plug?...

Lower the tank, and weaken and break the ARF by cutting formers, etc.

Not a good idea if you have to go this far...

Didn't you point out this was a beginner's forum?

Doing this correctly is beyond the reach of most beginners.

If help is available to them, it's another matter altogether though.

The engine doesn't care that it is inverted once started.

There is NO measurable "fuel pressure difference" over the 1/2" differentials we are talking about.

Your engine should not change when inverted in flight too even with the throttle pulled back to idle.

PRIOR to start fuel can siphon which can lead to initial idling problems until the excess fuel is flushed out ( which can take longer than some may think ).
In turn that can cause you to mistune the engine which makes it seem that the engine is more sensitive.

Typically though you can tune the engine upright, then mount it inverted and it will run the same way.

If it doesn't look to starting proceedures and plumbing problems. Fuel may be flooding the head because of tank height/siphoning.


On my inverted engines I will sometimes loop the fuel line over the mount, to raise it and prevent siphoning altogether. (I drain the line when I'm done flying).

However this causes fuel to siphon BACK into the tank, so I typically have to hit the engine with the starter for 10-15 seconds before it grabs enough fuel to start, but once started there is no problem...

... No need to do anything as drastic as what has been suggested, e.g. cutting up your ARF.

This is a much simpler solution BUT once fuel fills the line, it can continue to siphon... so I merely keep the throttle fully shut down after each flight.

Hmmm, So I suppose its good idea to go on ignoring the problem, then the first time someone forgets and hits the severely loaded engine with a good starter ripping the engine and firewall clear out of the airplane is a good idea? Most reasonable people would disagree and yes I have witnessed this more than once.

I have stated my opinon to the best of my abilitys and its growing tedious, I informed the orginal poster on how to get help and he seemed open to the idea in his last post in this thread I think he will do fine.

I will not respond in this thread anymore so oppose if you want to keep quoting me feel free. I am a poor typist and no longer interested in defending myself.

John

John I respect and like most of your posts, but I don't think you are right here.


You're assuming a worst case

- A starter should never rip the engine out at worst the starter will stall. Most novices DO NOT have high power electric starters and most use small starter cones that tend to loose grip when there is too much resistance.

This is no different than any other hydro-lock situation, but it is being thrown in for the sake of arguement, it is not a valid point.

- Most ARF's require a good degree of reworking to move the tank up or down as the ARF's are designed to fix the tank in the formers.

- Often this area is not accessible without cutting the covering, skin and fuselage, something that has to be repaired later.

- I'm sure you've seen the unsafe "repairs" novices show up with at the field. Advocating that they take a Dremel tool to an ARF in this situation could potentially be dangerous, far more so than the POTENTIAL for their starter locking up or spinning.

- Proper pre-start technique can overcome the relatively small siphoning problem. There is no real problem once the engine is started.

The frequent rehash of "tank height" issues is all too often mistaken to cause engine run problems, and that gets picked up and repeated by people who now have the wrong impression.... much like the "fuel stays in the back of the tank" myth which has been put to rest.


As such the proper advice would be to tell them to adjust the tank height to prevent siphoning, if it is at all possible without cutting the plane. If the latter is required, then they should seek the help of an experienced club member or use other techniques, e.g proper pre-flight, looping the line, etc..

Hi!
Tank height does matter!
This is a fact all of us have learned since "kindergarten years" in this hobby!
People that ignore this fact will have problems with there engine settings as fuel will run down to the carb when the tank is full and you have to lean the high speed mixture...then after 5-7minutes flying, when the fuel level has been lowered the engine feels this as a too lean setting and can quit!

The only way to fix this is to follow the simple gospel that every one of us that has been in this fanstastic hobby for decades knows about:
"Thou shall mount your tank so that the center of it, is in line with the carb" -Amen!

If thou follow this path you will be blessed with calm winds and forever return home with model like new!

Turn the engine sideways..The guys that did this are in the air while the inverted crowd is playing with their engines.