the best are the late a3/early a35 with the iskra points until the 2000ish a35s.
If you keep the points clean they are reliable for sure, but i had great luck out of 90's CDI A35 engines. Most reliable tomos i ever owned was a $100 Red TTLX that i had thrown a 70cc airsal kit, tecno hunter pipe, high flow filter, and 28T rear sprocket. I rode that all over Cincinnati and it never let me down. It ran until i traded it (with cash) for a Derbi GPR50RR.