Ohm checks on coils are nearly useless because they will only detect a failure that is virtually catastrophic and not common. Old coils break down internally from high voltage arcing across insulation. it only happens with HV applied, not a meter. In many cases it only happens when the coil is hot. I have a rule about coils: if they are old and I am having a spark problem, I throw them away. Z1 sells a cheap EMGO coil that works pretty well. I have run one for about four years now.
If you have decent voltage at the coil and a weak spark, it's probably a hosed coil.
