RE: K&B .65 Sportster
I've got one that was given to me years ago when K&B was in AZ. It was about wore out. Sent it to them for warranty repair(remember when the Sportsters had a lifetime warranty for almost everything but crash damage) because it was about wore out. They sent it back at no cost and replaced everything but the muffler, carb and drive collet. I still have it and I fly it in a Sig Kougar. I removed the baffle in the muffler and added muffler pressure. It runs like a champ on Wildcat 10% fuel with 18% castor and 2% synthetic. It swings a 13x5 Zinger prop which pulls the Kougar like a stripped *****ed ape. Almost unlimited vertical and unbelievable level flight speed.
Heck, I even had a Sportster 45 and a Sportster 20 on planes that I still fly. The 45 and 20 were bought before K&B moved to AZ. The 20 has an o-ring for the head gasket so this is how old it is. All engines run like a top and all have the muffler baffles removed and have muffler pressure.