HI ALL,
I am almost finished building my first plane,An lt40.I was planning on an OS 46 ax as everyone recommends.However for about half the price i can get an SK50a.It has almost same power as ax same weight and warranty does anyone know anything about SK engines.Nobody in my local club has one. thx ahead of time

Quite a few people here have good things to say about the SK but, if it were my money and I was wanting to save money rather than buy an OS, I'd go for a Thunder Tiger 46Pro. It has everything the OS has except the very high price tag.

There are a couple of long threads you can find by searching for SK. They are about both the SK 50 and SK 90.

A significant point in one thread, the engineer and member of the design team stated that when they designed the engines, they changed the port sizes and port timing to make the engines have high torque so they would turn a large prop. The smallest prop recommended for the 50 is a 12-5. The smallest for the 90 is a 15-6.

In addition, he stated they used very hard chrome plating such that it would take about a gallon of fuel to break in and the engine would gain power for 3 gallons.

People in the threads reported the engines tend to lean out in the air and quit and wouldn't transition. The engineer stated this was typical of the engine being under propped and run at too high an rpm (over 12,000 in the air or over 10,000 on the ground). After they went to the larger prop, the engine ran fine.

I ended up buying two 90s (actually .91) and one of the 50s (actually .525). The .91s run just great. I haven't completely broken in the 50, but it has run fine so far on the 12-5 prop. I will say that I did the exact break in shown in the instructions, then put the engines in Sticks for flying the rest of the gallon. The weather has gotten a little cool for me so I haven't flown the Big Stick 40 with the SK 50 in a while.

From my experience I would say that if you run the engine as designed with the large prop you will get good service. If you are looking for a speed engine to run a 10-6, 11-5 or 9-7 on, you will be disappointed. I think they are a great buy for sport planes and Sticks that can handle a long, 12 inch, prop.

I also have 4 of the OS .46AXs on twins and they are excellent engines, very easy to set up, plenty of power, very reliable. Since you are just getting started, the AX would be a better choice as it requires very little break in and can run a smaller prop. Even better would be an OS .40LA or .46LA. They are plain bearing engines and lower in power than the AX, but they are easy to run and made primarily for trainers. Don't fall for the old line that you can use a ball bearing engine in your second plane. By the time you learn, you'll probably bounce your plane off the ground a few times and you'll want a new engine for your second, and higher performance, plane. You also might want to keep your trainer and engine to fly in club events, to warm up before you fly your acro plane or to put on floats.

Hi Ed,I want to mention that my SK50 and a friend s (new) one absolutely wants more prop than 12x6 :Some RPM checks(with a borrowed Tach) showed more than 12000 RPM s on mine(no nitro) and about 12900-13000+ for him with some nitro.(mine was 11x7 APC his was 12x6 other than APC-forgot the brand)

hI ALL
THANKS FOR YOUR RESPONCES.
I DECIDE TO BUY THE SK50.
LOTS OF REASONS PRICE A BIG ONE

I'm assuming that the SK 50 would also be happy with an 11x6 (that's what the Kangke site recommends). I might want to try one in something like a Kwik Fli one day which has trike gear. A 12" is just to big for grass fields.

According to the engineer, the site and manual are incorrect. He told me he plane to correct it. The prop sizes were for the previous engines they carried. I know the engineer states in another thread that a 12-5 was the smallest prop to run.

I know Turk runs an 11-6, but he lives in Turkey and uses no nitro fuel. I would go no more than 10% and listen for a lean run. He stated that a characteristic of the prop being too small was the engine running lean after about 5 minutes no matter how rich it was set on take off. Listen, or have your instructor listen, for leaning out after several minutes of flight.

Yes I know all about this I will be turning a 12x5 or maybe even a 12.5x3.75 We'll see what she likes best.

thx

----------------


As you probably know, diameter is only one way to increase the load. Stick with an eleven inch diameter prop and crank in some pitch to compensate. Besides, if Kangke recommends an 11x6, you could also use a 10x7 or 8 to apply the same load to the engine and make it happy, while gaining prop clearance. Can't wait to get my SK .50 and .90 mounted up and running.

The wife's new business has taken off and has consumed my "shop". That's why the delay in getting things going again around here. I miss the space, but money is nice too. <G>

If things keep going as they are, perhaps we will be moving to a larger home with a separate shop for my uses. I can handle it.


Ed Cregger

Best for you Big Ed,wish new year brings you as wishes in your deep heart.Im waiting to hear your experiments on SK.

---------------


Happy New Year to you and yours, my good friend.


Ed Cregger