Originally Posted by R1ffR4ff

If you have a multimeter it's worth checking the Spark plug caps.Set it on the 20k Ohm setting and test the caps.Stock they have a 5K ohm ceramic resistor in them.As they age the corrosion on the contact points inside and the resistor can increase the overall resistance.Once it starts going North of around 8K ohms they can cause all sorts of problems like bad starting/engine cutting out and misfiring and rev limiting.





They came in around 1980 ish but not long after Spark plug makers started fitting 5k Ohm resistors into the Spark plugs so this over complicated form of Spark plug cap is not even needed if using,"R" rated Resistor Spark plugs but motorcycle makers still fit them as standard.

I used to run both my old hondas with none resistor caps but with,"R" resistor Spark Plugs,no problems.

They were/are fitted as a filter to reduce the possibility of Back EMF(Electromotive Force) that can cause problems with other components in the Ignition system and not as some people believed as Radio suppression.

Even as recent as Yesterday my M8 came round to tell me his bought-from-new Triumph Street cup had just been fixed as it kept cutting out and it was Faulty Spark plug caps!! :O