The following is what I have learned about Norvel engines from people who have flown them for decades and whom I consider to be top notch engine tuners, who strongly keep longevity in mind. I have had great success following these procedures, though they do vary from NV Engines publications. I won’t repeat their methods here, but I do believe they are written for people who are not necessarily familiar with performance engines and find the startup to be extremely frustrating. Their method will get it going more easily, but, I believe, at the expense of premature wear. Read their information and consider it before you follow my advice. I’m an amateur modeler and cannot back up my methods with any sort of research. Please proceed after your own consideration of all options.
Read all of the tabs on the following page at NVEngines.com
http://www.nvengines.com/index.php?option=com_content&view=category&layout=blog&id=45&Itemid=18Now, here is my method:
Once it's mounted in the test stand, leave the muffler off if you have one. These engines have a tight pinch at TDC between the piston and cylinder wall that makes it difficult to start the first few times. Try to resist flipping it over cold before you run it, as this unnecessarily wears the tight fitting P/C.
Since your AME is meant to run on pressure, if you start it up on suction only, mount your fuel tank with the feed line as short as possible and the internal pickup opening of the tank at least as high as the spraybar of the venturi. You can go higher, but beware of flooding, and you might want to clamp the line when not actually cranking to prevent gravity feeding the engine and flooding it. They are not friendly when flooded and can even bend a connecting rod if you try too vigorously. Do not use an electric starter, for this reason. A spring starter can be a big help. Anywhere from 15% to 25% nitromethane will make it happy. I currently use Sig Champion 25, and an extra dollop of castor in the jug is fine if you have some. Never use less than half castor in a castor/synthetic blend, and no less than 20% total oil. If you have any castor-only fuel, I would recommend that, but don’t sweat it if you don’t have any. That’s only my own personal opinion. Make sure the fuel line is full of fuel and ready to go, clamp it off if necessary, but don’t connect it to the engine yet. Have the glow driver turned on and ready as well.
To make it easier to flip start, especially with no spring starter, it helps to reduce the compression by adding a couple of extra head gaskets. If you have any Cox copper gaskets, they will fit too. In fact I got frustrated flipping my first Norvel and put a low compression Cox Babe Bee head on it and finally got it started, and ran it that way for one run. Since then, I know a better way, and if you follow the following instructions, the Norvel head will do fine.
The combustion heat causes metals of the piston and cylinder to expand from their cold state to form a perfect fit and let the piston move freely without the hard pinch. So to help that process along, heat the cylinder good and hot with a heat gun. This naturally relieves the pinch, making it easier to spin. Once hot, immediately connect the fuel line. Prime the venturi and give it a few brisk flips, then put a couple of drops in the exhaust. Connect the glow driver and give it a rip. Sometimes back flipping is easier, especially if you’re right handed. Either direction will fire it off. If you see it running backwards it’s just burning off a flood. It might straighten out and kick off. If it’s flooded badly, clamp the line and flip till you burn off the flood.
Once it’s running, find the needle setting for a wet 2 cycle, then turn it on up to full speed. This engine needs heat and speed. The P/C needs immediate heat to fit up properly. Once it warms up, back it down and go back and forth between a brief wet 2 cycle and peak full speed for an ounce or so. Do NOT run it sloppy rich as this will not maintain the necessary heat to keep the pinch loose and will cause excessive wear. After an ounce, clamp it off and let it cool. Do this for several ounces, going back and forth from a brief wet 2 cycle for cooling, to a screaming peak, stopping and cooling completely after each ounce. When it will hold peak indefinitely without heating up and slowing it's ready to go. You can now go back to normal compression if you previously reduced it.
It may not be fast at first, but it will keep breaking in as you fly it until it's really an all out screamer. I also think the 6x3 prop recommended by NV Engines is too much for it(possibly another dumbed down idea for easy cranking). This engine is meant to run higher RPMs than a 6x3 will allow. I would use at most a 5.5x3 for the first run, or even less. If you use APC props, a 6x2 will get it up there, but most others need to be shorter. Remember, the AME needs high RPMs to draw fuel, and will need pressure for flying. A bladder is my preferred fuel supply.
I have 3 Big Migs, and one AME. Once they start really breaking in it will turn a 5x3 prop about 23-24k RPM. I have three Big Migs that are now fully run-in after flying and they will all turn a Master Airscrew GF 5x3 at around 25-26k. But it takes a lot of running to get there. Like I said, as you fly, it will continue to break in. My oldest Big Mig will spin an APC 5x2.5 at 28.8kRPMs. Your AME should blow its doors off. In fact, on my one little AME powered combat plane, I use an APC under 5" long with a 3" pitch
One thing I like to change right away is the prop screw. The supplied screw does not reach very far into the crankshaft. I like screws that go in deep, so I use replacement Black oxide hex head screws that are 3mm x 25mm. I also prefer the ones with an un-threaded shoulder as it fits the Norvel spinner better.
Have fun and come back and let us know how it goes.
Rusty