Derailer/pedal misses "help"
Hi people first time poster and am back into cycling after gas went past $3.50 ga
I have a diamond back mountain bike from mid 90s in excelent shape,,,however when I ride it, about every third rotation of pedal sprocket it misses and pedals just dont engage just free pedal,,,Im sure its the derailer thats either missing or maybe gettig bumped by chain,,theres no teeth missing from any gears and its not comming from the pedals or pedal sprocket,,,does anybody have a checklist I can go through to try to pinpoint the problem
any help would be great