G'day Crabman, what 090 said.
also they do have a weak spark anyway, make sure the gap on the plug is correct (from memory 0.030" i will check book) as this will also help.
in my case i had an intermittant fault with the CDI.
84' & 85' models are similar (difference part #) 86' on have different mounting (not sure if functionally the same, but i suspect not, as stator is also different) i had a spare i bought of ebay (seller said it came from running bike, but it was also stuffed, this caused me lots of grief as i assumed they both could not be faulty).
i was very seriously looking at a PVL for mine, but the cost was the issue at the time and another ebay item popped up for around US$100 and the exchange was good at the time. i had already spent way too much by this stage and i could not justify the extra.
good luck and report your findings here.