I am back on the grinder after reading about the change over in ignition from BME to falcon. I see were the timing is different. I am wondering is this the way for me?


Well I took my spark plugs out and notice that my spark is arriving about 12/6 o’clock. That would explain my kickback. I loosen that setscrew on the prop hub and make the spark come about 10:30. With this new setting, I try to start the motor, three flips good choke pop, choke off, and she is running. No hesitation no extended idle. I still need to set the timing to the correct spot as I did the (TLAR) that looks about right. I am there from what I can see. I will have to readjust my throttle linkage so that I can kill the motor she is idling at 1200 and the low trim takes here to 1050 were she is still just a running. I am at 6000 rpm by ½ throttle and 6330 at full throttle. I now get instance throttle down on full to idle.

Albatross

you were on the money so many post ago for this particular deal. i will now go to the C & H site to download my wheel....

Krayzc, the actual spark timing is the same both the Falkon and the CH ignition. The reason the timing ring has to be changed is because the CH ignition is set at 28 degrees before top dead center (full advance) and it RETARDS the ignition timing back to 2 degrees BTDC when the engine is started. The Falkon is set at 2 degrees before top dead center because it ADVANCES the timing up to 28 degrees BTDC after the engine is running. Notice that in both cases, the engine starts at 2 degrees before top dead center, and by about 3,000 rpm, both ignitions fire the spark at 28 degrees before top dead center.

I was on my fourth Ch Ignition (in all cases, one side stopped firing) so the prospect of a more reliable ignition was good news to me. Each of my BME 110s received a new Falkon ignition. I flew it last weekend, and can report that the engine ran exactly like it did with the CH ignition, when the CH was operating properly (firing both cylinders). My only reason to move to the Falcon was to increase reliability, and time will tell.

Tim,
That is interesting.
I sent my ignition in for this problem before and they replaced both coils.
After about 150 flights, it started happening again and this time I fix it myself.
What I found is that the phenolic spacer shifted and let the circuit board touch the case.
When I fixed this, it ran just fine.

Tim about how many flight (guess) or time in months are you getting before the iginiton starts to go South? With my igition being to far advance do you all know what the symtoms would be besides kickbacks? i am trying to see if the hanging idle that Geistware
sees may also be a few degrees off.

Tim did you do the swap out yourself for the falcon? i would have to also change my plug setup on the 100. I will keep this deal until a failure comes along and if the falcon is working longer i will go that route.

Krayzc, be sure to read the instructions you find at the CH site regarding setting the ignition timing. When you say the spark arrived at 12/6 o'clock, I'm not sure where that is. Did you mean the prop is at 12/6 o'clock? It's more important to know where the piston is, and you'll see in the instructions that the piston's position is expressed in terms of degrees of crankshaft rotation. Top Dead Center and Bottom Dead Center mean that the piston is exactly at the top, and bottom, respectively of it's travel. Top Dead Center (TDC) is expressed as 0 degrees and BDC is expressed as 180 degrees. Proper spark timing at full advance for your Bemmer means the spark should fire when the piston is going up and is exactly at 28 degrees of crankshaft rotation before it reaches Top Dead Center (BTDC). Your ignition should automatically retard the timing to 2 degrees BTDC which would then allow it to be started without kicking back.

Another thing, if you're standing in front of the plane and moved things from your 12/6 oc'clock to "10:30" that implies you advanced the timing significantly (over 25 degrees). If you're standing in back of the plane and moved things to fire the spark at 10:30, that means you retarded the timing over 25 degrees. Another thing to take into account is the direction you rotated the prop when you noticed your spark firing. If you had a degree wheel to time the spark, you'd see it fire at one place when you properly turn the prop in the normal direction, and you'd see it fire about 25 degrees more advanced if you rotate the prop the other way.

I know the engine is running now, but I'd REALLY be interested in knowing exactly what the timing is now.

Miles, when I opened mine, there was no evidence of a circuit board touching the case, everything was placed where it should be. All I know is that even with the case open on my work bench, with a fresh battery and my CH ignition tester driving it, only one plug fires, and I'm welcoming a change. I had even kept a spare $200 CH ignition so I wouldn't get caught 100 miles from home at a contest and have an ignition put me out.

I'm hoping that the new Falkon proves as reliable as it has on the ZDZ engines.

No particular time, one lasted several hundred flights, another less than 100.

Like I said before, I don't think his is an ignition problem. He said it occured mainly on landing approach, and I'm thinking it's simply because the prop is lightly loaded and windmilling until the plane is on the ground and stopped. Mine does the same thing with both ignitions.

I did it myself, but I already had degree wheels, dial indicators and stuff from another life when I used to build drag bikes for guys. One thing that I also use, and heartily recommend is the CH ignition tester ($22) that allows you to test both the sending unit (pulse switch) and the ignition itself. This allows you to more easily and precisely check your present timing, and set it exactly where you want it.

I would definitely suggest that as long as your CH works for you, keep it. Yes you would have to change spark plugs, but CH has a 14mm to 10mm adapter for the new plugs.

Tim,

I will be printing off a degree wheel off of C & H so i will know more to tell you. I stuck a straw into the piston hole to see how far the psiton was coming up prior to starting this deal. I did all of the movement from in front of the plane. I turned the wheel clockwise, that wheel being the one with the set screw, this is turn made the spart move from the prop being 12/6 to the 10:30 area. This made the piston come up futher before the spark happen. Before i could turn the prop from 12/6 to about 10 before the piston hit my guess with the straw at TDC.. Does all of that make any sense? I should be back on it soon still plugging away at the home remodeling thing.

Gware make sure you still look at that low end being lean....

Yepper, first things first on the remodeling. When you get the chance, though, keep me posted on what you find with the timing. I know that you were feeling that the initial timing was too advanced. I do know that if, as you said, you did all movement from the front of the plane, and if you actually did turn the hub ring clockwise as viewed from the front, then you actually advanced the timing rather than retarded it. Think about it ......... viewed from the FRONT the propeller's normal rotation is counter-clockwise. If you loosen the set screw and rotate the hub ring clockwise (as viewed from the front) then the pulse switch trips sooner than it did, as in timing being ADVANCED. To retard the timing, the hub ring must be turned counter-clockwise, in the same direction as the prop spins, again, as viewed from the front.

Anyway, the engine is running as you said, and whenever you get the degree wheel set up you can figure out exactly where your present timing is, compared to where you want it to be (28 degrees before top dead center when turning the crankshaft in the normal counter-clockwise direction as viewed from the front).

Krayzc,
If anything, the low end is rich.
I have played with oils, mix ratios and everything.
It is just the nature of this engine.

Tim_Indy
i put on the C & H degree wheel the timing was at 5 degrees. i reset it the timing to 28 degrees and talk about a kickback/backfire in the exhaust on choke. This baby is in bad shape (C & H). I will be converting over to falcon after today. I did not even want to reset it to back were the engine would run once it kickback i packed her up and took a plane to the field to maiden flight....

Heard that ...... apparently the Synchro Spark circuitry that retards the timing for starting is faulty. Main thing is that now your know exactly where the timing is. Now setting up your new Falkon won't be a problem.

BTW, what new plane didja maiden and how did it go?

Tim

i maiden a accel katana all went well with an OS-91 set-up

krayzc-RCU,
If you get tired of playing with that engine, I can take it off your hands immediately!

should have bought a DA,, GERALD<<<<<<<

jongurley
i did buy a DA its been used on the regular to keep my papers from blowing while i keep my fan on HIGH!

hell don't any of those guys pay my bills. i will take an OS, BME, Brison, ZDZ, DA, 3W, Satio, or a rubber band and a good lite prop. A well turned motors runs well in my book for my needs. i am pass that phase of lightest, newest and all that mess

now on the real deal i can only run a 26 x 10 prop on my ultimate because of prop clearance any good newer 100 will rip that prop like its cool

I will be puring again in the coming weeks wiht my falcon yeah baby!!!! oh yeah the motor is fine, now we won't see on how it gets its spark

Tim what does the new pick up look like? can you snap a pic?

I think you have a glitch in your "check the timing setup" a BME won't run 6300 RPM with the timing set at 5 deg BTDC.

OK, WHY??? []

That would be the max advance at high RPM, and that would be to retarded for any engine to develop much power.

First of all, I'd think it EXTREMELY rare (almost never?) that the timing ring hub slips from the factory setting, causing a change in the ignition timing. Even if it is suspected, one should accurately check to see where the timing is, BEFORE moving the ring and changing the timing to something else.

Having said that, I first suspected a flooded engine, caused by flipping the prop with the choke closed, then turning on the ignition and flipping the prop to start it. This is solved by first turning the ignition on, then closing the choke, flipping till it pops, then open choke and flip 3 or 4 more times till it runs. Krayzc was doing that, and still getting kickback, so my next suspect would have been the ignition itself not properly retarding the ignition for starting. As I mentioned before, the CH ignition is timed at full advance, and it retards the ignition timing when you are trying to start it. Krayzc said it ran NORMALLY once it started, which also would verify that the timing was still at the factory setting. The fact that it kicked back pointed to the possibility of the ignition itself malfunctioning, and not properly retarding the ignition during startup.

The fact is, the fuel mixture doesn't burn instantly, rather it takes time for the flame front to travel from the spark plug and completely burn the mixture. Because of this, it is necessary to light the mixture earlier (28 degrees before the piston reaches top dead center) so that the pressure is building and by the time the piston just passes top dead center, the expanding gases exert maximum pressure to drive the piston down the cylinder. Ignite the mix too early (advanced) and pressure builds too fast and actually fights against the piston while it is still going up. Heat builds, detonation and pre-ignition enter the mix and work to destroy the engine. Ignite the mixture too late, and pressure builds too late to effectively drive the piston down. The fire is still burning when the exhaust port opens, and energy is wasted out the exhaust pipe.

That's the reason that tkg wondered about the ACTUAL ignition timing here. Since the CH is set a maximum advance, if the timing was actually set at 5 deg BTDC much of the energy would be going out the exhaust pipe rather than pushing the piston down, and the engine wouldn't have nearly the normal power since the spark is being lit over 20 degrees too late.

Before one can get accurate readings with a degree wheel, the setup has to be correct so that when the needle reads zero degrees, we know that the piston is EXACTLY at top dead center. If one simply sticks something in the spark plug hole to feel the piston coming up, the zero reading can fluctuate up to 15 degrees either side of top dead center, which is a 30 degree swing! This is because turning the crankshaft doesn't move the piston much at top or bottom dead center. One needs to use either a dial indicator or a positive stop to accurately zero top dead canter. Then, all other readings will be just as accurate.

I'm still suspecting the ignition itself isn't retarding the spark at startup like it should, rather, is staying at full advance. That's why it can rev up with normal power, but kicks back on startup. At prop flipping speeds, if the mixture is ignited while the piston is still going up (28 degrees BTDC) the pressure drives the piston back down and the prop goes in the reverse direction (kick back, and yepper, it BITES!). Retard the ignition so the piston is at top dead center when the mixture ignites, and it can't kick back.


PS - Trying to do all this thinking has got my head hurting!!!

OK, I know how a 2 stroke works, so you guys are saying that the advance is set to max and the ignition unit retards the ignition advance from 28 degrees at idle and 0 degrees above 4000rpm.

I was under the impression it was the other way around.
With this said, if the advance/retard fails, then the engine will still run but will be hard to start.

Some manufacturers do it opposite of CH, both work well.

I'm saying that with a CH ignition, the timing is set with a degree wheel so that when the crankshaft is turned in it's normal direction, the spark will occur while the piston is still coming up, at 28 degrees before the piston reaches top dead center. This is the normal full advance that allows the engine to run well and be powerful. If the advance/retard fails, yes the engine will run normally at speed, but will definitely kick back when it's hand started. To prevent kickback, the CH ignition is designed to electronically retard the timing at hand cranking speeds so that rather than firing the spark when the piston is still coming up, the spark is delayed until the piston is about at top dead center. (We may be saying the same thing, I dunno)

I also said the Falkon ignition is set at 2 degrees BTDC because it electronically advances the timing to the 28 degree BTDC when the engine accelerates. If the Falkon unit's advance/retard fails, the engine will continue to start easily, but will have no power.

I'm starting to think that rather than adding to understanding, I may have contributed to more confusion regarding this stuff. I do know that proper ignition timing is one of the key ingredients to having an engine that runs strong, and runs happy. Without understanding, it is easy to get things out of kilter.

OK, now I know we are saying the same thing.
The only difference is that I thought the C&H unit worked like the Falkon unit and it doesn't. They work opposite