the rotary suction valve has been used even in early 70s suzuki, kawasaki kh and a lot other motorcycles, It has good timing but has bad airflow as the carby is placed at the side of the crankcase, High performance setups always have reed valves like the yamaha rx/dt/enduro, honda H100 engines had - they flow a lot more than rotary valves and specially show their superior performance at high rpm.
Most problems started when local Pakistani mechanics took apart the reed and tried to "tune" it by widening the stopper plates (bad idea) and then had no idea why the plates would come loose and get pulled into the engine and destroy it (the recommended procedure is to apply threalocker to the holding screws) - hence the legend of "khara cylinder fail hai"
for average motorcycle mechanic in Pakistan - that blue residue on the screws was "jenyan speshal chemical" and they though it was not available outside Japan.