I've had 2 Maico's w/the stock Motoplat ignition fail. The common failure mode for both of them was that they became increasingly difficult to start, then they would only light off by push starting, then not at all. So both received new PVL's. My 81 started acting really strange at the Boise Inter AM and quit making spark altogether, this was with a 5 year old PVL. I removed the unit and sent to Penton Imports for test, the stator coil was bad, very high resistance reading. Note: Steve at PI told me that it is not uncommon for the older style tape wrapped stator coils on the PVL's to last only 4-5 years. PVL has fixed this with a totally encased stator coil on the new units. My 84 500 is now starting to exhibit the very same hard to start problem (only push starting will work) so I'm going to try an HPI ignition on the 84.
I find it interesting that the stock Motoplat units on these bikes lasted over 30 years and modern ignitions are lasting a fraction of that.
Hope this helps,
Fritz