Engine trashed in an hour...

No matter the viscosity of the oil, it is still present as oil in the mix.

Oil does not combust therefore fuel v oil content must be addressed.

Add oil= less fuel, that is why larger jetting is required to keep the AFR at the correct ratio.
 
In my opinion, that piston had NO LUBRICATION! An added "lean condition" may have contributed to the failure, but there was no oil, or very little there to do the job. Strait gasoline by accident perhaps?
 
In my opinion, that piston had NO LUBRICATION! An added "lean condition" may have contributed to the failure, but there was no oil, or very little there to do the job. Strait gasoline by accident perhaps?
 
  • Like
Reactions: Blaaster
I sure hope you did not add more oil to the mix, if you did you may have leaned out the AFR just enough to cook the piston!

Did you make sure that the header pipe was free of debris before you put it on?

If there was any crap in there it may have been forced back into the cylinder by the back pressure!!

It would have to be a absurd amount of oil to hurt anything, I have ran a. 20:1 gas oil mix with oil pump on 50+ snowmobiles for the first tank and have never had any issues, ever
 
IF the engine is sitting behind you, this will change how the engine cools and can sometimes make it extremly sensitive to jetting. I have done many experiments with enclosed 2 strokes and it is very difficult to keep things consistent when it comes to jetting/cooling the engine. I have seen engines blow up in 100' or less and it had no air leaks.
I'm guessing bad bore clearance and maybe some heat from???/ jetting
 
Adding oil to fuel for break in purposes is frowned upon unless the Jetting is changed to suit the diminished fuel in the mix!

What purpose does extra oil do anyway, the engine does not require any extra for break in!

The crosshatching in the bore can only hold so much oil the rest is thrown up the transfers into the combustion chamber to be sent out of the exhaust!

The pool in the crankcase should remain at a regulated level due to the crank picking it up and distributing it!

If the crankcase did accumulate more oil then it would be a pointless exercise as too much oil in a high speed rotating bearing can create friction resulting in heat.