Cleaning gunked up U/C engines

I used to dissassemble my engines right down for a rebuild/cleaning. Still do with Cox engines, but the larger ones now get heated up to free them, oiled and then bench ran with 50/50 castor synth. The Synth will take care of the varnish in short order. All the internal old junk will come out of the exhaust.

Now, if you want them to be pretty that's another story, best to break them down then.

For me the simplest and most expeditious way to clean a really gunked up engine is to just dunk it in the crock pot and boil it for 3-5 hours, disassemble while hot (can be painful), scrub each piece with Simple Green and a tooth brush, rinse in clean water, dry with compressed air, douse with spray Remoil, more compressed air and reassemble. Drop a little light oil in the exhaust port and venturi and spin over several times.

Just did this one this morning.

Thanks all. Several different methods, but should I be concerned about losing compression with too thorough a cleaning?

Maybe.

One method not mentioned is to part the cylinder from the rest of the engine, and clean all but the cylinder and piston.

It is a known problem that over cleaning an old engine can remove too much varnish making the engine worn out. There are not any good ways to artificially apply varnish. The engine needs to be started and run.

The "important" varnish is at the top of the cylinder. However if the engine has not been run enough to develop varnish, and associated wear, it won't matter as much. The only way I know to tell how important the varnish is happens to be by removing it. Visual inspection offers a clue too.

Phil

Yes, on any of the old-school, non-ringed, engines, one should never clean the piston and cylinder. You will just remove the all important varnish and loose compression.

A bit of "patina" on the outside is just part of the charm with old engines, to me, there is no need to make them pristine. Here is an example of what one can do with some regular kitchen stuff (old-school slight abrasive cleaner) and a toothbrush. It is almost too clean for me actually...

Having bought and cleaned well over 150 model engines of all types in the last couple of years I feel somewhat qualified to comment on this. Most of these engines have been cleaned in a crock pot.  



And shamelessly showing off my P-38 (yet again)



Early on I bought the cheapest most trashed engines that I could find .049's mostly, Cox, Testors, Ok's, Wen's.  Most were locked up solid and covered with caked on castor.  I tried solvents, boiling in Simple Green (don't do it, turns them black) and lastly a heat gun which worked to free them up but did little to remove the castor from the fins.  

Then Rod, bless him, mentioned the crock pot method.  I was amazed.  Not only did it loosen them up it made disassembly and removing the baked on castor so easy.  But as Ron mentioned it also removes the "varnish" on the piston and cylinder walls as has been discussed here over the years.

So concerned and moving on to larger displacement engines most bought cheaply because of their condition, I decided on doing some experimentation.  First I just warmed the engine until it moved freely and either ran it or attempted to run it.  Some ran quite good, others not so good some not at all.  I’m talking 150 + engines here.  

So, taking the not so goods to the crock pot and boiling them, disassembling and cleaning each part and reconstructing, I tried running them again.  (Sorry I get bored and have little else to do ), most ran better, some a lot better, some not much beyond a short burst.  

The reasons vary.  Some were one and done engines where the PO either couldn’t get them to run, or ran them once and put them away without cleaning or using after run and locking them up.  Others were ran nearly to death, others crashed and missing fins.  Some with ringed pistons, some not.  

It would seem to me that a "clean" engine would run cooler/better without castor buildup in the head and cylinder fins creating hot-spots and expansion in those areas.

On the “one and dones” or low time engines, boiling or otherwise isn’t going to remove varnish that isn’t there.  Others with a varnish build-up, I don’t know.  But, I’m starting to keep a log detailing the amount of varnish on the cylinders and pistons prior to cleaning.  Stay tuned.

So...ROD is to blame !!! I couldn't remember where I first saw the crock pot reference, having been cleaning everything with fuel or Hoppe's #9 over the decades. Finally couldn't stand it any more and got myself a small crock pot and strainer. The first victim was the O.S. that had powered my Kadet since the early 1980's.

Other than removing the carb, there was no disassembling before it got chucked in some hot antifreeze for a few hours. I was shocked at how the ancient, cooked-on crud and stains wiped off. The .35 was drained, oiled, carb and new 'O' ring stuck back on, and started up. Once all the antifreeze was belched out, the old dog took off, and has been dragging the rebuilt Kadet around since.

So, kudos to Rod !!!!

I had a thought that is approaching "dumb" regarding "artificial" varnish.  In the past I have used olive oil to season cast iron skillets.  This particular oil has a very low smoke point.  It also congeals into a sticky solid at a rather low temperature as a result.  

On an engine that was varnished but worn, and has been cleaned and is now too low compression to start what about pulling the cylinder and coating the inside with olive oil, baking, cooling, brushing, (maybe repeating,) then fitting the piston in.  The olive oil would create an artificial layer of a varnish-like material that would in principle be replaced by the harder castor varnish over time IF the engine can be started.

If the engine can be started what about adding a small amount of a low temperature oil to the fuel to artificially create varnish faster?  1 teaspoon per cup is about 3%...

This is also bringing us back to "is the engine worth saving if it is worn out and only running due to varnish"  With consideration for the statement of "expensive replacement parts are being made by some people now and should parts for obsolete engines be hoarded" Consideration for "this is a hobby and it is FUN" also must be made.

Phil

Acquiring neglected and gummed up engines is risky and as Phil questions - "is the engine worth saving if it is worn out and only running due to varnish" - my first answer to this is no unless the engine is eminently collectable or has some sentimental value.

Back in the day - engines such as PAW and Oliver Tiger diesels were really only expected to last a season of control line and were either rebuilt or replaced. They were quite often sent back to the factory for reworking. No engine will last for ever.

I have ended up with many non runners after cleaning and put them in a restoration "bucket". Usually - and, as an example, I will come across one sold for a song with a busted crankcase or bent crankshaft that will be a donor for piston, con rod and liner and I will end up with a very clean and pristine runner from the two (three in some cases!). Then I have a pile of drive nuts, prop drivers, original washers, tommy bars, cylinder heads ---- from these I can complete engines with these parts missing or damaged.

It is a question of scale - get an almost clapped out engine and spend hours looking for spares or trying to get it to run!!! - I know it is a hobby but a little frustrating not accepting an engines demise. On some engines, I can make a replacement cylinder liner to fit the old piston - making a piston is hours of work for me. A very rare engine I would spend the time, a Cox Bee - not so sure!

I have often thought about leaving an engine "varnished up" but it is potentially a rapid failure waiting to happen and I have witnessed varnished engines seizing abruptly. I wouldn't fancy seeing a carefully crafted aeroplane hitting the dirt because of an engine past its "run by date".

Luckily, spares and parts are still available for PAWs and Ollies but Frogs, DC, AE, Kingcat, ED etc - no spares and if you find one it will exceeds the value of the restored engine.

There is always a balance between collecting and running engines and spending a lot of time restoring them. I often see brand new engines on sale far cheaper than the golden oldies with a questionable history.

We all have a different slant on what is good or bad. I free up gummed engines with the application of heat and Hoppes No9.

One I have it turning I will run it with 50/50 synthetic oil/castor before cleaning. This gives me a clue of how long to spend on it.

Usually, a clapped out engine was stored (put aside) clapped out and not cleaned or lubed. Over time the castor has gummed and gives the impression of compression.

As stated, "This is just a hobby and for fun". Thats why I'm doing this. If they run, Great!, if not it was fun trying.
I'm just using every ones experiences to try to get the best result.
Thanks for all the advice, I'll post my results when I finally get around to doing this.
Dave

Kim wrote:So...ROD is to blame !!!  
.....kudos to Rod !!!!

Well I won't take the credit for the cleaning method because I only read about it somewhere on the web.  I'm sure it had been discussed here before I made mention.  Probably because I posted before and after pictures highlighting a very successful clean on a couple of engines Rene grabbed for me from Toledo swap.

I know I'm coming in late here, but that's only because I posted a very comprehensive opinion of the "Varnish" discussion which managed to vanish in cyberspace.  My thoughts have pretty much been echoed.  Cleaning varnish doesn't wear out an engine, it merely exposes an engine's pre-existent deficiencies.  If it won't perform without the varnish, make it look pretty and sit it on the shelf.  Then go out and find an unworn engine to do your flying with.  I've been guilty of trying to make an engine go at all costs.  Sometimes an ebay purchase can turn out an absolute jewel, disguised by a thick layer of neglect.  Other times, a nice looking engine can end up being a fishing sinker.  Luck of the draw when messing with old stuff like we do.  My only real experience of varnish has been that it made the engine tight & run hot.  Took me a lot of work to remove it and the engine ran heaps quicker & cooler.
Best of Luck Dave.  Clean it up nice & see what you end up with.
"The thrill of the chase".

2-stroke glow engines for R/C aircraft by David Gierke is the oldest reference I have for using a crock pot with antifreeze.

BTW I highly recommend this book at least for a read. The information included is extremely helpful.

Phil

http://www.amazon.com/2-Stroke-Engines-Aircraft-David-Gierke/dp/0911295305?ie=UTF8&psc=1&redirect=true&ref_=oh_aui_detailpage_o02_s00

One more thing, What oil and nitro content do these engines like in their fuel?

On the old-school Enyas and Veco etc. I use 20-25% all castor and 5-10% nitro (0% works too).

dht7788 wrote:One more thing, What oil and nitro content do these engines like in their fuel?

Except for a few cheap-skate diversions, most of my bigger than .15 engine get fed Sig Champion 10%.

I think SIG themselves recommend their 25% all castor oil fuel, and to be gentle on the nitro level.