[Shep]

1st thing I would do is check and clean the Spark plug caps.



Click here,



http://globalcxglvtwins.hostingdelivered.com/viewtopic.php?f=8&t=84



Eliminate the easy stuff before possibly going to the carbs.

 

[Shep]

So I went to the garage to do this, took the left side plug cap off and found it was broken as soon as I took the rubber end seal off (that was the only thing holding it together). So I reckon I'll get a new pair of plug caps first. I should still do the modification to take out the resistor, right? Especially if I go get some Iridium plugs (NGK DR8EIX).

Yes if the plugs caps have resistors.There's no need to double up if you use any NGK plugs with the,"R" designation.



If you struggle to find the Spark plug caps people on this forum have bought the none resistor(simpler and better) Spark plug caps from this trusted supplier who ship international,



http://www.wemoto.com/bikes/Honda/CX_500_A/79-80/



These are the none resistor ones used on the UK/Euro CX500s like my 1980 CX500s.