Calling all Sparkie experts

Here’s a question for all you spark ignition engine experts. I have a number of converted OS engines that I have been running on gasoline/castor oil mix. After many years of flying they really need a clean up. I’m sure that the high temps created at a hot summer day at Taft have caused some coating to form inside. Gas engines burn much hotter than alcohol fueled ones. Yes, I have measured the temps and there is a big difference on the same motor with different fuels, using spark ignition. Now that the rules are changed in SAM, I’m going to FAI fuel for cooler burning and more power.

Should I try to remove the varnish on the pistons and liners or leave it there? I have heard that it forms a protective coating and helps the seal. I’ve also heard that it will slow the engine down and needs to be removed.

I remember an article in RCM many years ago by IIRC, Larry Renger where he recommended Hoppe’s #9 to be added to ½ A fuel to help keep the varnish down. Of course, this is not on the OSHA approved list any more. Left some spark plugs in a jar of it for a year and they came out clean. Should I use the crock pot antifreeze trick? I’ve had good luck with straight Simple Green cleaner and elbow grease.

BTW, anybody have any OS35 or 25 pistons and sleeves? Old style baffle piston type, not LA, FP, FSR, XYZ, etc.

Thanks for the help.

Don't know about the Hoppe's #9 trick at all.

As for cleaning these old engines up do a search on anti-freeze in a crockpot. It does wonders. The congealed castor on the piston and cylinder are only robbing power, if the piston is loose in the bore it needs chrome plating, a new piston/cylinder or some other real fix. I'm not convinced that geled castor seals anything without power loss.

OS MAX looper P/L sets?!

I havnt seen any of those for sale since the 80's. Even then, I bought every set that I could get my hands on. I even tried sourcing some from Japan, through CLPA pen pals. No luck.

Complete NIB 35S engines and relatively cheap on eBay right now and 30s and 25s are a bargain with many selling for $25 or less. I put up a good used 30S recently and got no takers at any price.

I havn't seen any P/L combos listed on the Bay in the last 3 years or so. I guess that thy can be officially classified as unobtanium at this point.

You could allways try T+L. Tom may have something that you can use. I'll bet that he has a bushel of 30S units left over from 30 to 35 conversions. The smaller engines? Good luck!

>Don't know about the Hoppe's #9 trick at all.
>
>As for cleaning these old engines up do a search on
>anti-freeze in a crockpot. It does wonders. The congealed
>castor on the piston and cylinder are only robbing power, if
>the piston is loose in the bore it needs chrome plating, a
>new piston/cylinder or some other real fix. I'm not
>convinced that geled castor seals anything without power
>loss.
>
>Randy Ryan
>AMA 8500
>SAM 36
>I fly 'em all and love it!

Ron B.
F4Fguy

Randy:

You're absolutely,100% completely correct! But if you keep shouting this to the housetops,you'll be tarred and feathered and dragged into the town square and stoned by the GREAT GUARDIANS OF THE CASTOR BEAN and their minions.

Ron B.

PS: I'm not too sure about the antifreeze bit either.Dishwasher detergent and water do just as well,in my experience. The crock pot is good though.

Ron,

I haven't tried the dishwasher soap yet but Big Art swears by it. I've just found the anti-freeze does and imaculate job. I will say though that its hard on paint and anodizing, maybe the soap would help with that, I'll have to try it.

Hoppe's Nitro solvent really works on spark plugs. The stuff is available in gun shops. We used to toss spark plugs into the trash when they started to mis-fire. But that was when they cost 50 cents each. Now, I save them and clean them. I don't have a "crock pot" but several days soaking in Hoppes at room temp will get them clean again. (what is "room temp"? all rooms are room-temp.)

Floyd Carter

"A kind word and a gun will produce more results than a kind word alone."

--Al Capone"----

I swear by the antifreeze as well. I have cleaned a bunch of my varnished up engines with excellent results. There is an article on it in a fairly recent Model Aviation but not sure what month. Randy is right about it being hard on paint and anodizing. I put a nice McCoy redhead in and let me tell ya, it ain't red no more. Live and learn.

Tom

My face when I saw the blackhead

Floyd,

You are right about those spark plugs and Hopppe's. I just tried an NGK that I had put in the cleaner because it was "fouled". Ran great on my OS15 conversion without a miss. Of course, I'm using one of your transistor ignition systems that throws a 3/8 inch spark so it's probably not a fair test. One thing for sure, I don't check spark with my finger on the plug like all the macho older guys do. I think they are probably using their original coil condenser and batteries from the 40's and are in no danger of a high voltage surprise.

I bought a complete Vivell 35 cheap at a flea market. It had obviously been run some, and was pretty grungy. It cleaned up very easily with WD-40. I havn't had WD-40 work so well on glow engines. Bill Lee advocates soaking engines in a bucket of WD-40, but I have not tried it. Apparently there are solvents in WD-40.

Jim. I'm not certain about this, but I have read reports that claim that WD-40 is simply a mix of kerosene and alcohol with some perfume added. Am I right?

John & Mikey. Wow! I have never put my little pinkie on a spark plug to feel the joy of getting zapped! We are talking 20,000 to 25,000 volts here! Having been zapped by accident a few times, I have great respect for spark plugs. By the way, don't try this with your lawnmower or your car, because you will be greatly surprised.

Actually, spark plug voltage will not harm you: the voltage is high but the current is very small. The main danger is your muscle reaction causing you to jump or throw your arm into something solid or sharp that will will cause the real damage.

Floyd,

Yes, the danger isn't the voltage, it's the involuntary reaction that it causes that's the problem. I used to work on radars and TV sets. The insides of electronic equipment aren't finished off so nicely, lots of sharp edges and pointy things to hit.

Maybe the flip the prop and check for spark thing is a holdover from when the SAM guys were teenagers. An ancient form of the game of chicken. Looking at the wiring of some of their planes I can understand why they might not have too hot a spark. Twisted wire connections, ancient metal condensors, frayed wires, etc. All my stuff is hard wired and powered by nicads. No way I'm going to test by "hand." OK, you win, I'm a wimp.

My feeling is that there aren't many people on SSW forum who actually "play" with spark ignition engines. However, here is a little factoid:

The generally accepted value of ionization in air (spark) is 70,000 volts per inch between pointed electrodes at 1 ATM. A test spark of 3/8" indicates a peak spark pulse of 26,250 volts! This might seem like "overkill", but actually not. The graph of ionization potential vs pressure shows that it becomes more difficult to create a spark inside an engine at peak pressure of 8-10 ATM, which is the case at piston TDC. Spark plug gap in model engines is typically 0.015". Even so, it takes a really healhy voltage pulse to successfully fire even a 0.015" gap at pressure.

These days, with NiCd cells (or Lithium-poly) and transistor coil drivers, most of the old problems with spark ignition in model engines has been eliminated.

Interesting, I've always held the head and plug tip to feel for spark, its just a jolt almost like a muscle spasm, which I guess it causes, not painful or frightening. I have to say though that I wouldn't want to feel it repeatedly!