William Robison
Posts: 20269
Joined: 11/10/2002 From: Mary Esther, Florida, FL, USA Status: offline
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Jorge: I have a little Magnum GP 25 that's about as old as its size, roughly 25 years old (maybe only 20, don't really remember when I got it) that has flown from new on a Goldberg Eaglet, it and the airplane are still in excellent condition. About 15 years ago when I was bashing my first "Big" home-built twin I got a used Midwest 40 size trainer, it had a Magnum XL 46 engine in it. That engine impressed me so greatly that I canceled the order for a pair of OS 46 engines and got another pair of Magnum XL 46 engines for it. That plane is still fine, and the original Magnum XL 46 engines are still in it. I fly them with Zinger 10x6 three blade props. I've also flown these engines satisfactorily with 12x6 MAS. I don't like APC, so I don't have experience to comment from. Since that time I have not bought another new OS engine. I have gotten a couple in trades I'll admit, and one trade I made just to get the new OS 46 FX engine on the plane. I wanted to see how long it would run before it peeled the liner. Sad to say, that &*^% OS engine is still running fine. It has been a big disappointment. I still have a pot full of K&B ringed 40 and 61 engines, when they are a good fit I'll use one (or a pair) of them, but when I want a two stroke screamer it's always a Magnum. I have never been displeased with one. Anyway, that's my story. I have to admit hearing not such nice things about the Magnum XL 52 engines. One of my local flying buddies, who also happens to be a twin flier has not been able to get a pair of 52s to work in a twin, and others have posted about problems with them. I've not had a 52 size Magnum, so I can't comment on that one engine. In the larger engines the XL 108 and now the XL 120 have been no problem, it's just the 52 that I hear nasties about. Fuel. Home mix is fine, hope you are using some castor oil in it, doesn't have to be all castor, but at least 3-4% castor, and 15-16% synthetic is OK. At least 18% total volume of oil for the Magnums. For break in run the engine at full throttle, richened about 500-600 from peak. Do this for a couple tanks, then fly the plane at the same setting. As you fly it gradually lean it out until you're flying 200-300 rpm off peak. Start leaning the idle as you lean the peak, when you get it consistent at 300 rpm off peak you should have the idle set also. One problem. The Magnum engines are set up for 15-20% nitro. Pull the head, pick the head gasket out, put the head back on. This will raise the compression, it will run better on zero nitro that way. Do this before you run the engine, with everything clean and new you should get a good seal without a gasket. If it leaks you can lap the liner to the head to get the seal. Hope this helps. If I've missed a question yell at me, I'll make another post. Bill.
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Real Airplanes have Two Engines AMA 25139 - More than 40 years.
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