Chainsaw Repair

Couple things .It would almost seem to me on that engine with the induction straight into the crankcase it would have to have either a reed or be a rotary valve .My guess seeing the induction is though the blind end of the crankshaft that it's rotary . With no piston to block the crank case pressurization on transfer it would have to use some means to check the flow .

I would be curious to see the port roof angle on the secondaries /boosters or what ever you call them .It would seem to me they'd be steep blowing upwards towards the head deck else straight accross towards the exhaust port they would seem to short circuit .

Very interesting design I must say .An old gent on the west coast once had an 090 Stihl renown at one time as the fastest  on the coast .Could be true or an urban legion .

Never the less although he did not go into detail he stated it used a set of secondaries though piston  windows ,through a set of reed valves for the boosters .He never gave any specifics  of how that was done .