Yes, Fox is an interesting engine brand. When I was a teen flying control line in the mid seventies, the Fox .35 and Combat .36 were fantastic engines. I never had a problem with them. Of course, that was when Duke was still running the business. Fox engines are very powerful, but their design is so dated and the internal fit has alot to be desired. That and there are so many places for a Fox to leak, particularly around that full length back plate. Their carb needle threads leak badly, too. I tried to get a NIB Fox .50 to run recently. Running 20% castor, 10% nitro, I could never get the engine to break in.... ran hot as a firecracker. Too much compression I suppose. I substituted a Magum .52 XL and away I went, no problems.