Plug gap
 

Ok I know this seems to be a pretty basic subject and seems wouldnt need much discusion here. Anyhow my stock ryobi ignition i was running a plug gap of about .025. It ran fine with that gap. I then bought the rcexcel ignition and installed it. the thing runs just great till full throttle when it would experience momentary cutting out in ignition. I know this is not a carb issue as I put the stock ignition back on and it ran just fine. Ok so sitting in my garage thinking on it really hard I decided to play with the plug gap. I first went larger which made the problem all the worse so i knew I was on to something. I then set the gap down to .019 and it stopped having the misfire at full throttle. I did not get to run it to long to confirm this as my wife came out to the garage with the old why are you messing with that look when you got other chores to do. I will go back out and run it some more tonight or tommorow morning to confirm this. anyhow What gap are you guys running on your stock or electronic ignition. I read the rcexcel instructions again and it just didnt say anything about plug gap. My findings so far are that the electronic ignition dosent much care for to wide a gap or at least the stock ryobi gap.

RE: Plug gap
 

The RCEXL unit should be able to fire .025" OK.

RE: Plug gap
 

I agree with Jim it should fire it fine, but stranger things have happened. My DL50 will run OK with no misfire at .025" but it turns a tad more rpm's at .022". My nephews DA50 will misfire only at full throttle with a gap of .025" much like you describe. I've seen other DA50's run fine at .025" so I'm not sure what gives here. I just run mine at .022" to .023" and all is great in model airpane world from my point of view.

RE: Plug gap
 

I guess I could start opening up the gap .001 at a time and see where the problem comes back at. I wonder if i got a weak box or if the high compression that has been built into this engine could afffect this. I know it gets harder for the spark to jump the gap under pressure. I will play with it tommorow.

RE: Plug gap
 

I am thinking it is because you have a bigger spark with a larger plug gap that you want .025 inch instead of .019 or.022. Right? But what is the problem if the engine runs better (read OK) at a plug gap of .019? Any downsides? Thanks.

RE: Plug gap
 

They idle better with the wider gap but sometimes at high speed you have to close them up some.

RE: Plug gap
 

That is true till you add in pressure. when you increase the pressure of the air fuel mix that the spark has to jump it increases the resistance and in effect you have a smaller spark. to offset the increased resistance one would decrease the gap that the spark has to jump across. so one could say that the size of spark is inversly proportional to the pressure at which it has to jump a set gap.

RE: Plug gap
 

The plug can have conducting deposits on it, and at .025" perhaps the current is leaking through the deposits instead of jumping the gap at high pressures. I once read a study that showed that most "cleaned" plugs required more voltage to fire than a dirty plug!! I would try a new plug. The RCEXL should work fine at .025". Load check your battery, and/or check it's voltage with the engine running.

If it just doesn't want to work properly with .025" after doing the above, hey, just set it at .019" and run it....

AV8TOR

RE: Plug gap
 

So, in a very high compression Diesel engine the plug gap should be set to zero? :D

Sincerely,

SPACEWORM

RE: Plug gap
 

My diesel doesn't have a spark plug

RE: Plug gap
 

Damn thats funny.

Anyhow I loaded up and went out to the airfield today. the engine and ignition didnt miss a lick at the .019 gap over several flights. This ignition may be able to handle the larger gap but for some reason the particular unit I have really likes the .019. Im gona run it at that and problem solved lol

RE: Plug gap
 

Looks like you have found the sweet spot

RE: Plug gap
 

I don't know, maybe its naive, but I always gap my diesel plugs at zero....

;)

AV8TOR

RE: Plug gap
 

Guys, I have discovered that diesels can work without spark plug!Try it!

RE: Plug gap
 

Spark plug, glow plug, what's the difference. Mercedes Benz still uses glow plugs in their Diesels (don't they?), useful on cold mornings. And, if they weren't gapped at zero, it would be like a burned out glow plug with no continuity in the element.:D

RE: Plug gap
 

Having to go to a smaller gap is a sign of a weak ign. Ran into this many times when running a small engine business. .025 is pretty well standard plug setting. Replacing the coil usually fixed the problem to get the voltage back up to par.