My OS .91 was a gift because the fellow couldn't get it running right. I gave it a new ring and a tune up, it's in my Kaos. Sorry but I have rebuilt three Magnums this year, all .91s and the oldest one was three years old and the other two only two years old?? It was the rear bearing that was the problem on all three but I replaced the front bearing and ring while they were apart. The ones I see at the fields are either working or having problems. Each sale has different items and the Xmas sale doesn't have the Power Master 15% on sale either, the 20% is 19 dollars though. They do have the 52 XL on sale for 115. I'm not following the glow engines a lot because of the price of fuel and the new prices of them. Just too much money and I still have a few not being used. I started going back to gas this year and will only have three or four glow powered planes in the next year or so. I got over 10 years of very hard use with my pumped OS 1.20 before it needed a rebuild. As much as I like that engine I would never pay the kind of money they want for one today, the gas engines are a much better deal and cheaper to use, that and I have a couple under the bench needing a home.