your right about firing twice per revolution, accidentally found that when strobing by old AG100 [cdi ignition], had me head scratching for a while but thought in the end--nothing to stop it doing that!!. Had an MX250b new in"75 'with the two step' trigger [retard & advance]--same type set up as the DT360A except for the full flywheel. Anyway the MX went strong right out of the box then next year"76 YZ250C mine was a slug compared to year before. Took me frustrating ages to find an answer as mechanically identical motor. But found the ignition was [too trick for me] so strobed it & found it advanced to [i dunno] lots, say 36 degrees then retarded off gradually to bloody near tdc at full revs so though bugger it & just over-advanced it on the backplate which fixed it, didn't ever give any problems. BUT--asked the Yam factory mechanics that came to our work with the importer [they were doing the rounds & we were to line up a few problem jobs--was fun watching their methodology for working it. They were on to anything we could throw at them--damn. Anyway, asked them [why] re-ignition & they said we do that to stop you blowing it up by over-revving. Bugger that i thought [in those days] give me power. Cheers.