Didnt you forgot to mount the metal parts between the clutch sleeve and engine casing?
There are 2 parts in between : cast alu and steel sheetmetal....
Fair call on not wanting to buy it because youd only use it twice a year, but the damage youve described doesnt sound bad at all, new wheel clip ons...
If it was running great before, I would not change the plugs because of standing around. How was it standing, was it standing on the tires or die you...