The old OK Cub .049A was my second engine.  The first was a Cox Thimble Drome .049.   I could use the short reach plugs in the Cub and for me started a lot easier.  Fuel at the time was Testors 39 and later K&B 100.   Prop was Kayson 6-3 or 6-4 when the shop was out of the 6-3.Used that combo on a lot of the Scientific kits.   My favorite was the American Boy.  Back then I flew in my back yard with Daycron lines about 20 foot long.  Finally got out to 35 foot cable .008.   Don't remember rpm as I never checked it.  Still have the engine some where in my stash.   When they cane out with new Cub .049A a few years ago I bought two if them.  What a waste of money as I never did get either one to run.  They would pop and have short bursts of running, but not long enough to even think about flying.   I went through the changing plugs, fuel and props.   Even remove the insert on one of them that was in the intake.   Yes they would draw fuel if choked.  I finally gave them to someonme who thought he could make them run.  Never heard from him again.  Hope yours work.  But as Ty says make sure you have castor in the fuel.

A friend gave me a new Cub 049 a and I don't want to ruin it, so what fuel should I run in it? All castor, what percent castor, nitro, what sort of engine R P M and what size prop, how much run time to break it in??

 Any other info that will help...         Thanks

A prop between 5x3 and 6x3. I have run them on 5% nitro but they needle much better with 15%-25%. Since they are low compression engines they like a little more nitro. Lube should have some (or all) castor and be in the 20%-22% range. I broke mine in with several two minute runs followed by complete cool-down (heat cycles).

My newer Cubs have a needle with very little taper. They go from slobbering rich to full lean in less than a turn. I added additional taper with a file. Works fine.

As mentioned these engines were designed in the early fifties so don't expect a lot of power. One of the "hollow log" kits or something with about 18" span should fly. I like Cubs. 

George

John i bought several new OK engines 049 and 06 and had the same result. Couldnt get them to run
properly.

Bruce

Ok i will try that, thanks George

Bruce