[TonyCapobianco123]

Ive heard the term "loading up" many times over the years while wrestling with an uncooperative motor but have never understood what it means and whats really going on, Can someone explain please?
Thx
Tony

[stegl]

You may get other definitions but my "loading up" is were fuel builds up inside the crankcase on 2 stroke engines and the motor starts running too rich and usually dies or quits.
Always a good idea to get an experienced person to go through with setup with you.

[Terry Gauvin]

Yeah loading up normally happens at idle, when the idle is way too rich. When you then try to transition from idle to full throttle the engine spits and sputters and may quit rather than throttling up. Assuming tank position is correct, leaning out the engine at idle will cure the problem.

[Cougar429]

The previous posts are accurate, but there is a bit more that can affect your "Loading Up" problem.

First off is engine condition. If brand new and not broken in it will require a richer mixture to keep running and that can lead to build up in the case at low throttle. Once that break in is complete you will be able to lean it out a lot more and the problem should reduce a lot of go away completely.

The same can happen with an engine that is worn out, suffering from excessive clearance between the crank and case, as well as low compression. Not much can be done with the first problem, (and that was one that came new with some engines I will not mention here) but a new ring and possibly liner if worn can resurrect a high time plant.

Second could be tank position. If too high you will have a hard time setting a reliable mixture. You want the tank half level to be even with the inlet port on the carb.

Another is engine mounting. Inverted creates its own set of problems in that often the carb on a 2-stroke is now much lower and the airframe may not allow for the tank to be lowered enough to compensate.

Along with carb position is the tendency for fuel/lube to pool in the top of the cylinder, washing the glow plug and cooling it off so much it cannot continue ignition. That becomes more of an issue at low throttle and can be especially bad if it happens while engine is off and you go to start it again. That fuel can create what is called "Hydrolock" where an incompressible slug of fluid is in the combustion chamber. Trying to force the engine to turn can damage internals.

Finally, the wrong glow plug can cause the engine to act the same way. For example, my "Go To" plug for normal 2-stroke ops was always the OS #8. Worked pretty well through the season with good performance. Where it started to fault was if I flew in weather near or below freezing. It would act as if it loaded up at low throttle. The solution was a hotter #3 or even a 4-stroke "F" or their "R" from their rotary. These much hotter plugs would compensate for the lower temp environment and fuel.

The last 2 were also my only solution to keeping an inverted 2-stroke running regardless of outside temp.

If you are able to provide some more info as to make, model and mounting could hope to provide more specific solutions.

[floyd]

All the above are true. The newer OS 2-Strokes can load up at half throttle and the engines can quit in the air. The low end adjustment can account for up to 80% of the mixture as you increase the throttle, until the high speed needle takes over. I always run a hotter plug than the OS #8. And make sure the low speed needle setting isn't rich. After idling for 5 seconds the engine should transition to full throttle without any hesitation, otherwise it will be always loading up in the air or on the ground. Cheers Floyd

[TonyCapobianco123]

Wow, thanks guys for all the good info. Its much appreciated.

[TonyCapobianco123]

So would it be realistic to get the low speed mixture screw set lean enough that it could idle for say 30 sec to 1 minute without loading up and have a good transition to full throttle without hesitation? Is this reasonably doable or am I expecting too much?

[floyd]

Originally Posted by TonyCapobianco123

So would it be realistic to get the low speed mixture screw set lean enough that it could idle for say 30 sec to 1 minute without loading up and have a good transition to full throttle without hesitation? Is this reasonably doable or am I expecting too much?

That's exactly what I do, but idling in the heat for too long isn't that good either. I run all my engines one click from lean on both needles. My engines can idle and never hesitate when giving throttle. If your lean on the low needle the engine will go flat or stall when you increase the throttle. I find the newer OS engines a little more sensitive to adjust, I'm talking the ones with both needles on the same side of the carb.
Cheers Floyd.

[Cougar429]

Once an engine has normalized and broken in it should be able to idle all day long and still transition smoothly to full throttle. I have honestly had little issue when the engines are mechanically sound, fuel is good and basic settings to start.

With OS and most of their copies that starts with the High Speed, (HS) needle 1 3/4 turns out from LIGHTLY bottomed with the throttle wide open. That open throttle avoids any mechanical interference with the LS needle and idle bar if that is the design of the carburetor. I have seen some where the HS and spray bar assy can come together at closed throttle so always open it up to do this setting.

The LS needle usually starts with the end even with the end of the actual barrel alloy, NOT the throttle arm assy some use where the throttle arm is centered and locked on with a cap type arm more commonly used on 4-strokes.

These settings should at least get you started. Once fired up and engine warm go slowly to full throttle and then set the HS needle to peak RPM, then back rich, (counterclockwise like opening a tap) a click or two. You can even hold the nose up to see if it leans out and compensate for that, as well.

Once that is done you can slowly lower the throttle and below half you will now definitely be into the range controlled by the LS needle. In fact, Floyd was correct; the LS needle controls mixture from idle to approx 3/4 throttle and only above that does the HS needle hold sway. To think of it this way, the LS needle controls minimum flow, while the HS sets max flow. The two have to work together and the HS can strangle the flow if not set correctly first.

As the throttle is lowered slowly and in steps adjust the LS needle for a smooth reliable idle. As mentioned prior if the engine is new or worn out you may not be able to do this. At least if new you can expect after a few tankfuls it will normalize and allow for leaner settings.

The end goal is to get a reliable idle down where you are comfortable and it does not keep trying to pull the plane. In grass this is easy, but on pavement even the lowest idle will still yank the plane away and can be a problem if not restrained.

Normal transition to full throttle should be smooth regardless of length of idling and as mentioned I can get that on a good engine if the carb design is good, as well. Some makes were problematic and I often swapped in an OS carb as they were of better design and manufacture. Again, will avoid mentioning which engines this was the case.

That throttle opening should also be smooth, not hammering down the pedal to the floor. It should take a second or two as there is rarely the need to open it any faster in normal flight ops.

If too rich you would see the engine stumble, smoke or gag, then clear itself and increase RPMs to full. Lean it out very slightly and try again.

If too lean you can see a reliable idle as well, but it tends to die completely upon throttle opening. Increase mixture a bit and repeat.

2-strokes can normalize much quicker than their more complex 4-stroke brethren since they fire more often, but if loaded up like your original question could build up in the case and take a bit to clear. This is why you want to wait a bit after each setting.

You also want to do small incremental adjustments. If new and cranky you may find the "Sweet Spot" difficult to find an very sensitive if you do. This should be less of an issue once the engine is broken in and if the carb design is good allow for a wider range of mixtures before it adversely affects performance.

NOTE: It may be normal at first to see black residue in the exhaust, as well as a lot of oil smoke or droplets until you are able to lean it out. If this remains or shows up later you are likely experiencing more internal wear than normal and should investigate before damage becomes excessive. One of the worst offenders I encounter are bad bearings of low quality right from the factory or from cheap replacement sources. They usually don't last long.

On that subject, a good After Run Oil, (ARO) is recommended, especially 2-strokes that allow for it at the end of a flying session. This can negate any remaining fuel/nitro, (the latter combines with atmospheric moisture to create a highly corrosive mixture and you definitely do NOT want that attacking engine internals) and film protects it against attack. It also provides an initial lubrication on start up.

I made my own from a 50/50 mix of Air Tool Oil, (basically turbine oil used in real turbine engines) and ATF, automatic transmission fluid. Did this since worked with both and was available. Either is perfectly adequate alone. I have NEVER had any negative effects on rubber Orings or seals with this, although specialty engines such as YS may require something else due to their regulator diaphragms.

Not mentioned yet are fuel quality and prop. If the engine requires nitro of a certain content you should adhere to those recommendations. I found throughout my fleet of 2 and 4-strokes 15% nitro a good compromise for power and ease of starting. I use 17-18% lube quantity, mostly for the 2-strokes as 4-strokes really need less.

You should also stay within the recommended prop range for your engine listed in the sheets supplied by the manufacturer or available online. Another good source is to simply ask on forums such as this or at a local club since someone else may have found if one prop is better than another.

Here is an example: Over the years I have found Saito, (one of my favorite makes) often are a bit aggressive in their prop recommendations towards the higher pitch end of the scale. I usually try to go no further than their mid-range for best performance.

Having said that, I try to run wood props for early flights as this saves the engine if things go wrong. Only stay with them if presents better scale appearance. Most common I use and see are Master Airscrew, although APC is also widely available. Personally never liked them for scale appearance, but that is a personal choice. There were reports early on of their blades coming apart when used on 4-strokes. Never saw that myself.

As mentioned, wood is a good choice since it is often very rigid and efficient. Where it can suffer is age or environment where the wood can dry out, shrink or crack. They take close inspection for flaws to catch any failures ahead of time, as well as for tightness on the drive washer.

Other than Carbon Fiber, an investment I would avoid unless running a much larger plant, I especially like Graupner. Solid as a rock although a bit heavy. They have wide chord that work for both performance and appearance, the only negative is they can be heavy. On some scale mounts that can be useful, especially on scale radial apps where the nose is quite short.

As asked before, can you provide pics or more info on make and model? We may have more specific recommendations or ideas.

[biplaneFan]

Hi, I'm new to forum and following this thread too. I wanted to say thanks as well for replies to original question. I learned many things.