Perminator

Hi!
I've had a fair share of problems with an Evolution 100 that I've mounted on a UCD .60. It's been to rich, to lean and a bunch of other trouble. The engine's fine though... I've run it on a test bench and it runs flawlessly even with a Pitts muffler. The real problems occur when I mount it on the plane. At first I had it inverted but that was a complete no-go. Engine constantly floods. So I mount it horizontal and it's slightly better. Now it throws the prop nut and starts backwards and so on.

What makes a 2-stroke start backwards or throw the prop nut? Some one said it's to lean, another that it's to rich. This **** caused a flameout after take off today with a ripped out landing gear which punctured the wing and cracked the wing tip as a result. I suspect a tank problem but I had to go away for a week today so I've had no time to rip it out for inspection.

What do you all think is the problem here?

Rcpilot

My Feedback: (78)

I've never had a 2-stroke throw the prop nut. I tighten them untill I'm grunting and straining. Hold the prop and use a wrench to tighten it up. You should be putting about 50--60 pounds of torque on the prop nut.

I suspect that your not tightening the nut enough.

Running backwards:

Some 2-strokes just do this untill they get broke in. Flip it backwards to start it.

Are you running rediculous amounts of nitro? 5% or 10% is plenty. 15% or 20% is just wasting money--can cause detonation--and overheating problems.

The tank CL should be CL with the carb spraybar. If it's close--and the engine is mounted horizontally--you'll probably be fine.

Inverted engine installation requires that the tank and carb be absolutely perfectly aligned or it will flood as you found out.

Whats your altitude? Are you at sea level? If you are at sea level--then turn the needles out 3 or 4 turns and start from there. If it won't transition to full throttle--then it's too lean.

If you around 4000--6000 feet elevation--then start with 1.5 turns out and go from there. If it won't transition to full throttle--it's too lean. Richen it up a full turn and try again. Don't force it.

It is possible to get a lean engine to transition to full throttle with the igniter still attached. It will cook the plug and make the engine hot--but you can do it.

Take the igniter off and move the throttle stick. That way you will avoid accidently running at a lean setting.

Do you know how to do a "pinch test" to determine if it's too rich or lean? Pinch the fuel line. If it is running rich in the midrange and having trouble getting all the way revved up to full throttle---pinching the fuel line will make it run faster.

If you pinch the fuel line and it dies or slows down--then your too lean. Richen the needle by 1/2 or maybe even 1 full turn.

Don't worry about the low speed needle untill you get the high speed set right. Break it in first and then set the low speed needle. It's pointless to even mess with it untill the engine is broken in and the high speed needle is set.

Good luck

kelldog

My Feedback: (1)

Dont know about the prop nut dude but when you go to start a 2 banger and she starts backwards its a sure sign of to much fuel.Prop nut is a residue of the problem. KELLDOG

sport10

I first off want to say that all engines can backfire no matter if it is a two or four stroke. I have had an 1.60FX throw a prop inflight. Was not pretty. Check to make sure your low end is not too lean. This is what most likely causes backfires. If you are not using a double lock nut on your 100 you might want to consider investing is this safety item. Starting backwards is not real problem and can sometime be incorrect adjusted needles that cause it. Just try flipping the prop the other direction when starting. Lowering you nitro will also cause the engine to baulky sometimes. I am not sure what percent nitro the evo 100 is designed for but advise using what the manual recommends. Alot of pitts mufflers are not capable of delivering enough muffler pressure to adaquately supply the engine with fuel. Check to see if you can get a real rich mixture aka fourstroking if not you might need to plug one of the exhaust outlets or get a pump/pressure setup. Also, over propping the engine can cause problems like this also. Good luck

Sport

kelldog

My Feedback: (1)

Sportten, He did say starting up backwards. Which is one sign of many that there is to much fuel to start! The word backfire was never used. As you know rich starting engines are harder to turn over resulting in more of a chance of throwing a prop. PS. Wood props need to be checked often. Overtightening WILL SQUISH AND BREAK THINGS! And starting rich does not mean she will stay rich. KELLDOG

turbo.gst

My Feedback: (8)

Check the tank cl in relationship to the spraybar like rcpilet suggested. If it runs fine on the test stand, it should run just as well in the plane----IF the tank position,and all other things are consistent. To me, it points to a fuel tank or line issue if the tank position is fine.

The actual starting backwards, when on the plane, sounds like its flooded.

DarZeelon

Perminator,


Throwing the prop (and nut) is a result of the engine producing too high a combustion pressure, before the piston rises to TDC.
As Sport wrote, this usually happens with larger two-stroke engines, like the OS1.60FX and I have seen it happen in an MVVS 1.60 and in a Moki 1.80.


In a four-stroke, this only happens if the mixture is too lean, almost invariably at full throttle, resulting in a quick-to-ignite, fast-burn mixture.

As previously stated, the needles in any glow engine, directly control the ignition advance.
A lean-run is a result of too much ignition advance (not of too little oil, as some may think).


But in this case, it is a result of too much accumulated fuel in the crankcase, due to the low-speed needle being too open, or over-priming.
As the throttle is advanced, all this fuel suddenly rushes up, into the cylinder and its sheer volume raises the C/R to a magnitude, which results in the same early combustion pressure, as would too lean a mixture.



Don't over-prime your engine and close the low-speed needle to the leanestt setting, at which the engine will run and transition and this prop-throwing will become much more scarce.

Perminator

Thanks for all the tips, guys! Ok, the engines getting to much fuel, I think we've established that. I've tested the engine with the Pitts on a bench and it's got all the pressure it wants. I run 10 % nitro so it shouldn't be the problem either.

The spraybar IS pretty lined up with the tank centerline. I'm going to investigate the reason for the flooding a little more this weekend when I get home. I've got some repair work to do anyways

turbo.gst

My Feedback: (8)

If your engine is set correctly and runs fine on the test stand, look at the things that are DIFFERENT on the plane than the test stand. I know that if everything is the same as on the test bench, it should run EXACTLY the same. Now realize that a test stand situation is a perfectly controlled situation. You can visually see any problem. If the tank position is the same( on the C/L of the spraybar as indicated) and you are using the same prop, glo plug, fuel, muffler, you should be good to go. I don't know if you used the same fuel tank as on the test bench, but you could pull it out and check it on the bench with a little effort. For starters, the motor mount and fuel lines are different most probably.

It is not going to run great on the bench and sour on the plane. For starters, you have too much fuel when trying to start in the plane. Try to change how you are fueling the plane. Pinch off, or disconnect the line to the carb while you fuel your plane.
turbo

Kema

How is your idle rpm? Try starting at lowest possible throttle setting.

bkdavy

My Feedback: (1)

There's been a lot of advice thrown out here, but I'll put mine in anyway. On my 2 strokes, they nearly always start backwards the first start of the day. Why? I normally attribute it to too much fuel, since it generally occurs after I have primed the engine. I also flip start my engines using the backward flip method. Once the engine is running backwards, I use the throttle to drop the RPM as low as I can. The engine will either turn around and run correctly or stall. If it stalls, a forward flip start will generally get it to start correctly on the next flip. I then run it all the way to full throttle to clear out any remaining fuel buildup. You'll see it spit the fuel/oil out the exhaust. If it starts backwards, again, idle it down again and repeat. If your prop nut is not properly tightened, this backward running WILL cause the prop nut to back off and throw the prop.

As for the flame outs, this is a tuning problem. You must make sure the engine has been properly tuned, and this takes a little fiddling. With the engine running in the correct direction, lean out the high speed mixture to reach peak rpm at full throttle, then richen it 200-500 rpm lower (usually 2-3 clicks). Idle it down to its lowest reliable idle, let it run for 15-20 seconds, then quickly go to full throttle. If it sputters and dies, or sputters and then goes to full throttle, your Low speed mixture is too rich. If it just dies immediatly (no sputtering) the low speed mix is probably too lean. Make low speed adjustments in increments of 1/8 turn, and then readjust the high speed mixture as before. This is important each time you adjust the low speed. Continue to make these adjustments until the engine idles reliably between 2500 and 3000 rpm, and the transition to full throttle is smooth.

Unless there is a gross misalignment of the fuel tank to the carb, this procedure will account for the small differences between the plane and the test stand. Small adjustments in the low speed mixture are the key. Its very easy to blow right past the sweet spot.


Good luck!

Perminator

I'm going to remove the tank and take it apart, replace all the fuel lines etc. I installed it with two clunks, one for fueling and one to the carb. This is going away and I'm doing it like I've always done, one line with clunk for the carb and two brass pipes up in the roof of the tank.

As for the deadstick, I agree it was somewhat out of tune and I should'nt have taken off then and there.

I was to anxious.

Turk1

A clunk system for fueling?But why???

kelldog

My Feedback: (1)

I am not sure, but I do believe a 4 toker is better in this plane because of the tank position. Once you learn to not start her rich I would strongly suggest to get a glow with a idle bar to HELP KEEP her lit!! KEEPING THE RICH LITT IS A *****!!! KELLDOG