I have a K&B .20 Sportster that is 5 years old but unused and still in the box. I was planning to put this in a Great Planes PT20. I do not have any experience with K&B. Are their engines o.k. for general sport flying?
This is a great engine. Just make sure that you break it in properly. They take a little while to break in, so a lot of guys give up, convinced that the engine is a piece of crap. Hang in there and let it come up to top performance and you will be rewarded.
It's a very, very quiet engine. I had to take the baffle out of mine. With any other planes in the air, you couldn't hear if it was running. It wont win any competitions (not near enough power), but it is reliable. Use an OS #8. If it's cool out, a fox miracle plug. They can be a pain to hot restart without an electric starter. Make sure you have a good oil content fuel. I'd recommend buying a synthetic fuel, then adding a few ounces of castor to the gallon. I used a 9*4 and an
8*6 on mine, so the 9*4 would be a good choice for the PT. The 28 was the same engine case, punched out. It was lighter and much more powerful, and is a better choice if you can get hold of one. I have one of each, since the 20 wouldn't pull my Kobra. My 20 still runs, but I wore out the 28 on a Sterling Fledging. Taught a lot of people how to fly with it.
Last thing, don't use the nose gear mount/backing plate combo. The legs are ridiculously thin. It doesn't even make a good motor mount without the nosegear in it. Not one of their better ideas. BTW, do you have the book that came with the motor? The idle mixture is a bit different than any other carb if you haven't fooled with one.