What could have happened here?

[dirtbike]

Slightly out of topic but I hope to find some expertise here.

[DKWRACER]

Owch! looks like the exhaust bridge got hot, pistons should be drilled below the lower ring, for lubrication:(
Some piston kits came with the drill and instructions, hope that helps, adios..... Tom Brosius

[Kip Kern]

Simple:   ALL bridged exhaust ports always, always require lubricating holes drilled in the respective location of the exhaust bridge so as to prevent seizure in that area. All makes of motorcycles included![:0]

[tomale]

I agree, make sure you use the best 2 stroke oil you can find.  Not all oils are created equal. I know a bunch of guys here use  maxima products and with good reason.

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)
74' 1/2 440 maico
70' 400 maico (project)
72' cr125 Husky (project)
93' RMx 250 suzuki
Honda TL 125
2004 Suzuki DL1000