A crank bearing failure (worn out, not a broken cage) had this customer send me the engine back. Have any of you guys run Amsoil for more than one tear down? I doubt it if you engine looked like this. This is Amsoil run at 30:1 (most off road runs 25:1) for about 2 gallons of fuel in oval dirt track racing. The only parts I can save are the cylinder and cases. The ring has about a .100" gap (installed in the cylinder), the rod has a ton of side to side play, the main bearings are packed like a 20 year old Chevy engine full of sludge. The wrist pin is worn out and the top rod bearing. The piston is worn quite a bit (and probably what made the oil black).

This engine could run for "ugly engine of the week". Use a good oil, or you may wind up with this mess.

Doug @ ESP

I don't use anything bur Klotz RC in my engines and I mix it 16:1. Yeah, it smokes a little, but I have a Ron Buck engine that's 8 years old and still runs great.

Is that a Castor/Synthetic Blend? I use the Castor/Synthetic blend "Maxima Castor 927", but I think I would like any good Castor/syn blend. Even at 25:1 you see lots of lube on the piston/cylinder when tearing down the engine with the good oils. I have seen bone dry pistons with customer returned engines because of a department store oil @ 25:1. I have never seen a engine like our RC engines that show the difference between a good oil and a bad oil so easily.

After closer inspection of the cylinder, I found it was trashed also. I have never seen a failure like this before. Near the top of the stroke to TDC, about 10mm (height) of plating was gone all the way around the cylinder. The ring wore that plating out and the aluminum under it. I kind of doubt oil choice had much to do with this, but looks to be a possible manufacturing defect in the cylinder plating. That damage may have a lot to do with the dirt left behind and all the bearings worn out, and not as much with the oil as I suspected.

How has your Amsoil experience been?, because this problem I think was started by a manufacturing defect in the cylinder.