I bought a never been run Enya 35 Model 5224 recently.  This is the engine that comes with the hi and low compression heads and 3 different size venturies.  I have about an hour on the engine with the low compression head and small venturi.  It seems to be getting tighter the more I run it.  It does not flip freely like a normal engine.  I've broken two 9 x6 props lately from fliping it to start it.  Also, it gets real hot running a rich four cycle.  I'm bench running it using 10% nitro 26% castor with 2% syn. to make a total of 28% oil fuel.  I would not normally disassemble an engine but I took the front of the crankcase off and checked the rotation of the crank.  Nice and free.  Now being a Machnist/ Tool and Die Maker for 30 years, I do know something about what kind of fit operating mechanisms should have.  Figuring that the tightness is from elsewhere, I pushed the liner and piston out.  The piston is really tight in the liner, especially when it nears TDC.  It is so tight at TDC that I have to push the piston back down with a wooden dowel.  I'm talking using a 5/16 dowel, supporting the liner on blocks and hitting the dowel with the ball of my hand.  It is pretty much a light press fit at the bottom of the bore.  I've rebuilt some automotive engines and I know in them, your looking at a couple thousands clearance between the piston and cylinder.  I posted a picture of each side of the liner and piston.  You'll see the one side of the piston has some galling, that can be slightly felt with the fingernail.  With a bore light, I also found slight galling on the bottom side of the opening the exhaust port.  The liner is a silver to straw color towards the bottom where the piston is a tight slip fit and at the top where it is very tight the liner is blue on the outside toward the back of the engine.  The liner slips into the case with a nice slip fit and rotates freely, maybe about .001 clearance.  Now here's the scary part, I have access to a Sunnen hone...  I'm considering "dusting" the liner on the hone just until I get a slip fit.  And yes, I have experience using a hone.  It's not like I paid a fortune for this engine and it's some kind of jewel.  It seems to me that I have to do something to get a free running fit between the piston and the liner.  The engine is pretty much unusable as it is.  Any ideas as to what caused this, or ideas for a better solution than honing the liner?

Thanks Randy.  That's believable that it's a build up of castor oil.  That would account for the problem getting worse the more I run it.  Am I running to high of a castor content oil and that's the cause of the build up?  The Enya directions want 20% castor if I'm not mistaken.  I have fuel that is 10% nitro 20% oil 50% castor/50% syn. and I also have 10% nitro 25% oil 80% castor/20% syn.  Which would be better to run?  Also, what do I use to remove the castor oil build up before I lap it.  I also have had an Enya 29IVB since the mid 70's that is well broken in and that seems to run good on any fuel.

Hi

You can use the method above, or I use either Berryman's carburator cleaner or put the parts in a crock pot with antifeeze. Either will work.
I would use at least 22 to 24% oil and 1/2 castor 1/2 synth.
Make sure when you run it in to put the motor into a 2 cycle for 5 to 10 seconds then put it back into a 4 cycle to cool down, cycle back and forth in a 4 /2 to heat and cool the piston. You will not be able to break the motor in properly unless you get the piston up to temperature.
This is a common thing to do with Enya motors. I use to do this all the time with my FOX combat motors and even with FOX 35 engines.

Randy

I think you should ask yourself why the piston got this asymetric build up of carbon in the first place. It's most un-Enya-like, and not typical of an engine where all is correctly aligned. Brand new or not, you may have some distortion somewhere, or possibly a bent rod.

I have a 5224 that gave me fits running on 29 percent Castor.  It fouled plugs and would only run with a battery connected.  The general consensus was that it was flooding the plug with castor.  It does just fine on 22 percent half and half. In fact, I flew it today with great success.  Sucess for me means not breaking anything or scaring myself too bad.  But the engine ran great.

I bench ran the Enya with 25% 50/50 and it ran great.  I 2/4 cycled it like Randy said and after a few tanks it was able to run a full 5oz. thru it without slowing down or getting tight.  I guess it's broken in now.

Try Dawn Power Dissolver for any tough engine cleaning job. Years ago I had the same Enya engine only it was a .29. They were powerful engines but I never could get mine to run a 4-2-4 stunt cycle. It always had to be running minimum med. lean 2 cycle or not at all. That was with low compression head, small venturi, 10-6 Top Flite nylon, and no pressure. One day it quit cold in middle of wingover at a concrete circle. I had to drop my handle and run. My beautiful J-Roberts tri-cycle gear profile plane was a pile of splinters and Enya went to garbage w/ cracked block and bent crank.

My Enya 29 model 5224 also had the habit of shutting off in the middle of stunts.  I've lost more than one plane from it doing that.  I've come to the conclusion that my OS Max's are the most dependable.  I've recently bought a GMS 25 and a GMS 32.  I really like them a lot too.  Both the OS's and the GMS start easily and run great each and every time.