Lets discuss the Rcexl #4 ignition for a bit and the problems it causes. First, there is nothing really wrong with this ignition module except for its strange advance curve and some call it a step more than a curve. Most ignitions have an advance curve that is all in at about 4000 - 4500 RPM. The dang #4 has a curve that as ahicks said, is pretty much just an all in step at about 2500 RPM, which is just above normal idle speed and this is the problem. The #4 ignition runs just fine above about 3000 RPM or so. If you're having midrange or high speed problems with an engine, the #4 ignition isn't causing them unless it is bad. If you're having problems setting the low end, have problems getting a reliable idle speed or you have really strange problems getting the engine to settle back into an idle when you throttle it back or having problems maintaining a reliable idle speed in any way ..... the #4 is certainly contributing to if not causing the problem! AFAIK, the #4 was only supplied on DLE 20 engines. Within the last year, these engines now come with a more normal Rcexl ignition that can be identified by its lack of #4 sticker and a 4.8 - 8.4 voltage rating.

Unless a person is aware of the strange advance curve, the first reaction is to blame the carb when you experience any of the low speed problems listed above. While the carb could certainly be bad, in need of rebuild or adjustment, more times than not on the 20 it is that ignition curve causing the problems.

Here are some more symptoms .... have you tried to adjust the low speed mixture then the engine will just speed up for no reason? Or .... has it just slowed down for no reason, perhaps even dying in the process. .And we're talking maybe a 500 RPM or more changes here. Have you ever been on a landing approach, gave just a tiny bit of throttle to extend the glide and the dang thing just sped up so much it couldn't land .... and it wouldn't settle back to an idle so you end having to go around and try again. Or does the engine run completely different at the end of a flight than at the beginning? Yup, mostly caused by the good old #4 ignition. I should also mention that a less than precision throttle servo can also greatly contribute to the problem when this ignition is used.

Carb problems are usually consistent problems and not problems that require constant adjustments. If a carb is in good mechanical condition, is in a good state of rebuild with good rubber parts, has a good free moving and properly adjusted inlet metering needle, has high enough pop-off pressure, etc .... it should be consistent from one time to the next. Things that could cause inconsistency would be a worn or loose throttle shaft, throttle plate that is loose or just doesn't fit the bore well, dirt in metering passages, crummy cheap throttle servo, etc. Even removing or disconnecting the throttle return spring can contribute to the problem. Of course, rebuild the carbs when needed but worn throttle parts usually mean the carb is a throw away item.

Replace those DLE carbs if you must but don't expect miracles if you retain the #4 ignition boxes.