I found something cool I think Need a k&b expert

The Sportster engines have a high silicon sleeve and the piston has the top chrome plated. These are not high performance engines, they turn low rpm's. I prefer the .20 over the .28. These make excellent diesel conversions once broken in. They're quite heavy for their size but they make up for it swinging larger props. The Fox .19 and .25 are in the same case. The Fox runs quite fast and is a terrific engine and I believe the .25 is one of the lightest ball bearing .25's offered. They tend to vibrate a bit but they do run strong.

The Sportster line of engines are very high quality even though they were marketed towards lower end entry. These engines in my opinion will outlive the user. It takes a long time to break them in but when that happens, they're real sweethearts. I have all displacements and the .65 while weighing a 18 oz's, it's a remarkable piece of machinery.

George, Dennis is a close friend of mine. Dennis unfortunately developed severed neck and back pain which ended his fun in the c/l hobby.I've taken over Dennis's Sportster collection. I value them and I enjoy just running them. His advice was prop it like a 4 stroke and don't skimp on the oil and you will never wear it out. I totally agree.

George, one needs to own one of these and run it to appreciate it. The engine certainly isn't a high rpm barn burner but it is a tractor of a engine as your aware. My .20 Sportster swings a 10x6 quite impressively.  I also like that it's a very quiet smooth running engine. I really do enjoy these engines and I wish I had a Davis Diesel conversion for my .28. These engines run superb on diesel once broken in. They do take a bit to break in but in the end, it's very satisfying. It also amazes me how this technology carried directly into automobiles and larger scale engines. I suppose the same can be said about the Testor's plastic pipe bombs. Seeing that most intakes and other various top end parts nowadays are made out of similar plastics.

         I have a few different mufflers for the Sportster, the backplate mounts as you show. They may not all be stock but a derivative of header pipes cobbled with other K&B mufflers. Rod had mentioned about the screws stripping out in the main muffler body. I've had this happen to some of mine. I was able to place a T-nut inside the muffler to alleviate the stripped hole. By no means a easy task but it's doable and much more reliable.  I also have 2 .65's converted to control line. I have a very large Pat King Combat Streak which the .65 might be going on. I believe the engine is nearing 18 ounces so I might have to do a bit of a balancing act with it but it would be cool. NO ONE flies anything like that on a control line plane. The cylinder is massive but it spells cool factor x2.  This thread is going to make me get all of these engines out and running.

  On another note, I spoke to Dennis this weekend. I mentioned this post and the inquiries in regards to the Sportster engines. He said at one time he posted a lot of info on the Brotherhood of the Ring with many pictures involving many different topics. He said he was glad to know you remembered , all gone now and it was upsetting to him.

The machining is also done nicely. The only gaskets used on the .20 is a backplate gasket. The .20 doesn't even use a head gasket, the early versions had a o-ring but were found to be problematic. The .28 uses a head gasket. Looking at a .20 and a .28 is difficult to differentiate them apart. Some of the later .28's had .28 on the lug. All .28's have the crankshaft stamped with 28 on the crank web which is visible when the backplate is removed. These engines have no gaskets from cylinder to case. It was a engine designed to be competitive for a lesser dollar amount and it earned it's place serving a double standard. Most users early on used incorrect fuels or expected it too much too quickly. These engines won't tolerate being pushed and can seize. I have a .28 here that someone stripped it's life at a early start. Everything appears in order and but it has little to no compression. Parts for the .20-.28 are still available.