Hi Gang, Windy flying today in eastern Pa, but my plane came home intact. I am new to 4 strokes, just mounted an old OS 90 in my Global 60 hi wing. The fuel inlet on the engine is about 1 1/4" above the tank outlet so I put on an 8-32 pressure fitting on the muffler. The engine came with a screw in the hole in the muffler, have no idea why. Was this engine designed to use pressure to the fuel tank? I used 15% 2 stroke fuel, all I had and tried both a 12-10 and a 13-6, both worked but the 13-6 seemed better. I suspect I should go to maybe a 13-8?? I was getting quite a bit of smoke at idle and acceleration but not much in the air, normal? I used an OS type "F" glow plug. I found the hi end needle to be quite sensitive, not much adjustment needed to make big changes. I ran the engine and pulled off the pressure line, put my finger over the fitting, and was amazed at the amount of pressure created! Really quite a lot. I have no instructions for the engine, so if anyone can give me some pointers it would be greatly appreciated! BTW the guy who gave me the engine hadn't run it in quite some time, stiff and gummy, but I bench ran it to loosen it up. After about 5 flights I noticed the compression was considerably less than at the beginning. But, maybe I am used to hi compression 2 strokers! Should I be using 4 cycle fuel or do you guys use 2 cycle fuel? what about nitro content? Apologize for such a long post, but I am confused. Thank you all for any tips! Bill O'Neill Queen City RC Allentown, Pa.

Not an expert, but am running both O.S. and Thunder Tiger .91 4strokes for several years.
1. 2stroke fuel is good. It should provide enough oil. You might try 5% and 15% fuel, but 10% is likely just fine. We run 15% up here at 6300 ft.
2. O.S. "F" plug is the standard 4stroke plug everybody I know uses. I've also had good service from Thunderbolt 4stroke plugs for about 1/2 price...they come from Hobby People.
3. Your relative tank-to-needle heights are likely making the adjustment that picky. Getting them more level should help broaden the adjustment range.
4. Some of these engines come with both a screw and a pressure tap for the muffler. You done good using the tap. 4strokes don't draw fuel quite a well as 2strokes because they're only sucking half as often. With the muffler possibly injecting crud and metal bits into the tank, it's a good idea to use a filter between the tank and needle (as it is on any engine).
5. I've been happy with both 14x6 and 14x8 APCs on my engines.
6. Hope you're setting the needle with a tach or thermometer gun. It's nice to leave a light smoke trail when flying, shows plenty of cooling. It's easy to run a 4stroke ringed engine too lean and not know it. The ringed construction more easily trashed than ABC engines. Maybe it felt looser from running crud out of it.
7. Hope this helps, and that an expert will correct me if needed

I'm using pro pattern 20/20 in my 4 strokes. It has 20% oil and 20% nitro. You will need to set the high end needle with a tach about 300 rpm below peak. I'm running a 15/4W on a Funtana. If you get a 4 stroke lean it will have a tendency to spit the prop at you!

Check out the glow engine discussion forum for addtional information.

EXCAP232

I agree that for most 4 cycle engines, 2 stroke fuel is fine, and often preferred.
Dennis-

center of fuel tank to 3/8" below center of fuel tank to carb. needle valve is standard,at hi speed, pinch the fuel line,engine should speed up a tad [300 to 500 rpm]then point plane up,all speed should stay the same,low speed ,pinch the fuel line,the engine should speed up a tad.Two stroke or 4 stroke fuel its your choice