Help! New clicking sound.

[3yt]

My little 33cc windjammer developed a new clank.

-Started after 12 mile ride
-Not terribly loud, maybe a modest clapping volume.
-Single or multiple "clicks" on initial throttle or bumps.
-Cannot hear with bike revved at standstill/off bike/ or wheel off ground.

Other possibly related quirks.
-slipped chain a lot initially. Made tensioner from skateboard wheel, works alright.
-Not running an air filter atm, its in the mail.
-One engine mount bolt sheered off.

Pictures

 

[Frogslayer]

Sounds like it might be detonation. Try premium fuel and see what happens

 

[3yt]

Sounds like it might be detonation. Try premium fuel and see what happens

I did fill up about 7 miles into the trip, started hearing it about 5 miles later. I put 92 in it. Although, i might have put a bit more oil in than usual. would that be the cause?