Mc Coy 19- Need some start up help

The Mccoy is a neat little engine, unfortunately they can be short lived. This post is in regards to the Mccoy REDHEADS and not the rectangular Mccoy .19 series 21 Black heads. The first and most important fact about using one is the fuel. Use a minimum of 25% castor oil ONLY. A good hot plug is also in order. I'm not a Fox plug user (They will work however),  I prefer Thunderbolt R/C longs or equivalents like Fireballs or K&B L1's.  If you decide to use any other fuel, consider it a book end. I had brand new redhead Mccoy .19's wear out in one run. This was especially true with the .19's. The Testor's Mccoy series 21 engines used a ringed piston which was a Dyke's ring and these actually worked quite well. Many have switched the internals from the series .21 into the redheads for duration and longevity.  Keep in mind, this engine was produced for several years and the quality from one run to a next was all over the place. I'm not suggesting your engine is a POS or it will wear out immediately, my experience goes far back with these and I've learned a great deat about these engines as to the how and why. A 8x6 prop is a good choice, a Top Flite Super M if you can find one is even better  (Wide paddle blade). Realize the gaskets were inferior on those engines. Due to their age(40+ years old), they're more than likely dried out and no good. Breaking in a Mccoy is usually not a process. They usually wore out before they broke in. I don't mean to be sarcastic here. If new, run it rich on the ground a few times until it holds a decent needle setting and isn't shaking all over the place and go fly. These engines were under $5 at one point and pilots like my dad tossed them and bought another for the next weekend.  The screws they used to retain the head bolts are dead soft and only one type of screwdriver properly fits them which most don't have. My suggestion is to replace them with 4-40 1/4allen socket heads. I personally remove all gaskets and reseal the engine with high temp rtv silicone. This includes the head gasket as well which takes about 30 minutes to dig it out and properly clean the groove in the cylinder head. I don't reinstall a head gasket, I substitute the gasket for the RTV and let it sit 20-30 min prior to reassembly. This not only seals the head properly, it raises the compression due to it lowering the cylinder head a few thousandth's.

There's a base gasket between the steel cylinder and the case, these are the most problematic and if leaking, the engine is going to leak down compression and the RTV resolves this issue . I lap the case on a piece of glass with 400 grit sandpaper and oil to completely level and flatten the casting to provide a good gasket seal.  In addition, if you decide to remove and use the RTV as  gasket, the 3 and there are only 3 screws that hold the head on, they will be too long by 1/8" and therefore will require the allen socket heads to be cut. The ideal head bolt length is 7/8".

(These next suggestions are based on my experimentation and if you have hands of stone please skip the next step) This can and will ruin a piston if you have no experience with small engines


It's imperative that the nylon bushing or if you have the first version it has a brass bushing in the connecting rod on the large end. This bushing takes up the end play of the crank . If the engine feels light on compression, this engine has a very unique characteristic to it. It has a domed piston. The pistons are very soft and are susceptible to wearing out which is due to the metalurgy of the piston itself, it's not iron, it's sintered iron which was powder metal filings compressed under heat. This piston can be placed in the sleeve and put on a anvil or solid flat surface. I use a 3/8 steel dowel and a very light ball peen hammer and I place the dowel directly on the highest part of the dome and tap. This expands the sidewalls of the piston . Do not strike the baffle on top of the piston as this will break it. This process sometimes requires me to do this with the piston out of the cylinder which can really expand the top which now requires the piston to be lapped into the sleeve. I've taken completely worn out Mccoy's and made them run better than new. I've done this process repeatedly. If required, the piston is inserted upside down in the sleeve. I use a piece of 3/16" wooden dowel through the conrod as a T handle and I use Dupont #7 or toothpaste as a lapping compound and twirl the piston up and down in the sleeve. I do this at the bottom of the skirt until I can just get the piston back into the bore. I then resinsert properly and check the fit up at the top of the sleeve. It should pinch at the top. If not take it out and give a few more hits. Once the lapping is done properly, there should be a extremely shiny band around the top of the piston which is even for about 3/32".

Now that you read this and probably think I'm completely out of my mind, I would personally run the engine as is. These engines are like kits to me and I enjoy making them tick once again. Don't run it too lean as they don't sustain well to that. I would run it rich and use the fuel I recommend which is Sig 25% Champion or something similar like S&W 28% and see how it does. Removing the needle and placing a short piece of fuel tubing properly cut to the correct length  on the needle which will be squished up against the spraybar can resolve air leaks at the needle. Chellie provides gaskets for these engines. She's extremely knowledgeable about these engines. She's rebuilt hundreds of them and I'm sure you could e-mail here for a request of the step by step process on what she does to these engines.  Her how to lap in a piston is detailed and exceptionally edited for anyone to understand. Here's a link to her gaskets. She's the only one providing gaskets for the Mccoy's in the past 30 years. The quality of these gaskets are excellent as well as the fits.  http://www.ebay.com/itm/McCOY-19-RH-BH-Gasket-Kit-Nylon-Crank-Throw-Spacer-/131010858688?pt=US_Radio_Control_Control_Line&hash=item1e80db0ec0  If you need help, don't hesitate to ask. Ken