Hello Guys,
I have a Evolution Trainer System engine on my first plane. It has been running great until a couple of weeks ago. All of a sudden the exhaust residue turned black. It was a pinkish color, same as the wildcat fuel I use. The fuel is 15% nitro, 80% synthetic 20% castor on the lube end. I also noticed a black residue on my muffler that wasn't there before. I had the guys at my club check my needle settings, and they are convinced they are set right. I agree from all that I have read about tuning an engine. I tightened up the screw that holds the muffler together, although it wasn't loose anyway. The engine runs great at idle or WOT, and transitions good too. I'm just worried about the black exhaust residue. Also, it has started quitting when it has about 1/3 tank of fuel left. This has caused me several deadstick landings, not something I'm crazy about. Any help would be greatly appreciated! You all have made this a great hobby to be in.

Thanks,
Dan

Your .45 should not be quitting like it does. You say that wot and transition is good. Maybe it is time to check the plumbing from the tank forward to the engine. Clunk problems??? It is always a good idea to pull the tank, check the clunk movement, and replace the lines in the tank. If you suspect a clunk problem, cut the line in the tank in several places, and splice together using brass tubing. This prevents the clunk from doubling forward where it sticks and can't get fuel from the rear of the tank. May as well put new fuel lines on the plane if you go this far.