I have had a pair dl50 engines on my ziroli p38 for the last 2 years and the engines performed very well but they had the typical dl50 miss. Lately this has been bothering me a lot so i decided to try to solve the problem. I could tell the carb mixture adjustment was performing normal as the lean to rich sound was normal. So i decided to focus on the ignition.

I noticed other people on the dl50 post were complaining about the ignition timing being off on their engine so i checked mine, it was correct at 30 degrees so this was not the problem.

I took a look at the small stock dl50 supplied spark plug and with the spark gap less than 20 thousands of an inch i thought that maybe the grounding tab was shrouding the spark so the gas mixture was not reaching the spark on every spark firing.
So as an experiment i cut the grounding tab back to the edge of the electrode while still keeping the 20 thousands gap. I installed the plug back into the engine and started it up, the engine sounded better and after a test flight i did not hear even one miss the entire flight. My engine has never run this good.

i was amazed as how such a little modification affected my engine i wanted to share it with everybody.

mike

Throw the stock plugs, get ngk CM-6 5812 and you will not look back.</p>

Very cool that your mod helped so much. Interesting.

I toss the stock plugs no matter if they are good or not. I'm not messing around with my limited play time for all of $2.99 for the NGK CM-6.

This works too! Capt,n

Yes,
What you did, was create sharp edges to give the spark more "bite" and consistency. Spark energy likes to jump off sharp edges. It makes the spark hotter and more reliable.
What Capt'n john showed is a tuner's trick. Racing plugs have  very thin electrodes for the same reasons

So which do you think would produce the hotter more consistant spark?

No telling which.
both solutions have sharp edges. The one John showed however has more material left to dress again without increasing plug gap.

John, i am going to give the ngk plugs a try. i ordered a couple 5812 plugs from Oreillys.

Normally on a car the plug gap is around .035 to .060 inch so at .020 i thought maybee the gas mixture was not reaching the spark every time. The modification i did helped the junk stock dl plug so now that i know where the problem is. I am looking forward to seeing how the ngk plugs perform.

Thanks for the suggestions everybody.

Mike

I say the NGK plug is better quality in that the threads are machined better & the material may be better than the stock DL plug I have seen. Good threads are important as you do not want to mess up the threads in the engine head. It is a good thing to check the threads in the cylindder head too. Capt,n

Even the DLE dealers advise that chunking the stock plugs is step #1 in the installation routine.

I have the same miss on my DL 50.. I checked my timing, it was at 33 degrees, so I set it to 28 degrees. The miss is alsmot gone - more of a burble ( ground running). I then put in the filed CM6 plug - what a difference, the engine even sounded different at idle and runs fine at high end.
Thanks for the tip!

We'll see how it does in the air.
cheers - ken k.

The Mod shown in post #4 would in many cases cause the engineIdle to be 50+ RPM fasterand the engine would need trim to get the lower RPM level back. That was with no mixture change or any other change. Just the modified spark plug. Capt,n

HI,again flew the DL 50 in the GP Patty last night. air temp was +27C, a beautiful evening in Winnipeg.
1st flight last night was with the tapered NGK plug.
The high speed miss was gone but had a bit of a rich burble on full open, a lot better than it was on the weekend.
I then switched to a Denso plug (flying buddy is using them on a G26), the result was less of a burble with no needle tweaking.
I then leaned the high speed needle a hair each time, the the motor is now running nice, with a bit of high speed burble.

I could probably have leaned out the high speed burble out but since the engine is new (~ 12 flights) I did not wasn’t to push it.

I also gave the low end needle a bit lean and the the throttle transitition is much much better.

cheers - ken

A side gapped plug is a good easy cheap mod that can be a good benefit, I have been doing it since my old motocross days.

I used to do this to my cheap plugs and get the performance bump without buying a spark plug that costs 3 times as much.

There is one draw back though, a side gapped plug will foul easier than one with a standart gap, the reason is there is considerably less area available to spark to than a plug with a standard gap, thus making it less forgiving to being "gunked up". It's not a major problem though, just make sure the engine is tuned properly