Hi all, I’ve been a complete idiot and put 4 stoke Aspen fuel In my (second hand, but relatively new) 2 stroke/ 4-mix BR800 C. It ran ok for about an hour. then a week later when I released my mistake i drained tank and replaced with Aspen 2 stroke it ran for 10 minutes, died, and now will not restart. Can someone tell me honestly, have I ruined the whole engine? Is there any way I can fix my mistake? I know I’ve been an idiot so go easy,

Remove the muffler and look into the cylinder port. 
 
Look at the piston and if scored, the cylinder and piston are junk.
There's obviously other engine parts to wear but the piston is usually first 
and it'll show it.. 
 
 
.