Here are some pics of the 91' 40hp at teardown. Notice the lack of carbon on the top of the piston and the exhaust side is shiney not black and sooted. The good thing is I have an E-tec 40 to run while I rebuild the ol' 91' smoker. Inside the cylinder head looks like the piston on the left, very little carbon build up. I have been using a 1:1 mix of XD100 and XD50. I have to mix in the XD50 so I can see that the oil is mixed in the fuel. The XD100 is colorless when premixed. Not a good thing at 4:30 in the morn before a fishing trip!! [IMG][/IMG]