Jr25

My Feedback: (7)

I have a Zenoah G62 that although the engine is practically brand new, has sat the past 2 years. Starts on the 4th or 5th flip every time, and runs all the way up to top end without a problem or hesitation. The problem is at wide open throttle it has a slight miss. Almost like it is briefly starving for fuel, however, I can see the fuel line and there are no bubbles nor gaps in fuel delivery. Any thoughts or ideas what could be causing this, and how to correct it? For what it's worth, the origional mag ignition was converted over to a CH electronic ignition. Timing is at 26* BTC and the air gap is .0015. Running a brand new Bosch plug gapped at .0025, and 35:1 fuel mixture.

Thanks,
Jr

Ram Jet

If your ignition system is worth anything at all it should pull a .020" plug gap and possibly .035". I assume you are running gasoline. Run your engine at full throttle for a minute or two and cut-off the ignition. Pull the plug. If the porcelain is white your plug is too hot if it's black and sooty it's too cold. Ideally it should run with a light brick color. If you can get a very strong magnifying glass look into the plug at the point where the porcelain meets the metal plug body down inside. If you see little round metalic balls they are portions of your piston crown indicating it's running lean at full throttle. I personally would run a 20:1 fuel/oil ratio.

I'm assuming that you have elctronic ignition (CDI ?) I would test you ignition's "magic box" according to manufactuers spec. with a volt/ohm/miliameter. If you can find one in your heat range and plug size I would run a fine wire center electrode plug - your engine will love you for it throughout the entire operating range.

The condition of the spark plug is a good place to start. It's sounds like an ignition problem to me and probably not your fuel system.

Bill

driesbabe

Just Open the plug gap to 0.020-0.030 and you miss will be gone more than likely.

Jr25

My Feedback: (7)

Thanks for the tips. Although I have not inspected my plug under a magnifying glass, I have done as you suggested and the porcelain is a nice golden tan. I will 1st try closing my plug gap from .025 down to .020 and see if that helps. I gapped it at .025 because that is what the Champion plug that was in the engine was gapped at. For what it is worth, the .015 air gap I was referring to is the gap between my hall effect sensor and the metal pickup on the flywheel. This is what Terry at CH recommended.

Thanks again,
Jr

ww2birds

My Feedback: (14)

You might also consider the size (and condition) of the battery and the resistance of the wiring to the ignition unit.

While I suspect it is unlikely for a single cylinder ignition, I have seen cases on my multi-cylinder ignitions where too-small battery packs simply could not sustain the voltage at full throttle resulting in a miss. Had to use a 4200 maH (!) pack on a big 5-cyl radial.

The problem can be that a smaller capacity pack has a high internal resistance , or the too-small wires or switch also having too high a resistance. Either or both will result in the voltage delivered to the ignition unit dropping as the current draw increases, which it will do as the engine RPM increases.

What size (maH capacity) pack are you using, and is the wiring and switch good heavy-duty stuff?

FWIW Terry and the gang at CH are "A number one" for product quality and support .. if you are talking to them I am sure they will get you going properly.

Dave

Bass1

I tend to agree with a voltage issue (battery, switch, wiring).Have you tried by-passing the ignition switch and/or trying a different battery pack?

Doomking

My Feedback: (38)

I thought that G62 doesn't need battery packs to run the ignition....mine has the module mounted on the propshaft....
just a thought...[]

Big_Bird

My Feedback: (1)

Doomking, in his first post he stated that the engine was converted to a CH electronic ignition. That does require a battery.

Bass1

..Edit.. oops, Sorry Big Bird, I didn't see your post!

jerdavis

My Feedback: (3)

Maybe a too far advanced timing could cause a high speed miss. Recheck for the suggested timing. If you are using an on/off switch on the ignition, maybe you are getting switch bounce during levels of high vibration. Try eliminating the switch (for test purposes).

JD

jerdavis

My Feedback: (3)

Let me add that a bad connection, like a loose or broken wire, in your ignition power supply, that makes and breaks during high vibration will cause a miss. Recheck your wiring between the battery and ignition module.

JD