81 GS750LX spark plug cap

[Guest]

Hi i have an 81 gs750l i purchased earlier this summer for cheap..ie 400 and a 12 pack not running..but i got it running great so i thought, with the exception of holes in the right hand muffler. Until i went to change plugs to solve a little hesitation around the 3k mark...and the number 4 cylinder plug was white as white can be and wet..like never fired... and it had no spark to the plug but there was on cyl 1...but i saw a spark go through the cap to the cyl head on while checking cyl 4 with a new spark plug! So upon taking the cap off and testing it there was no connection to the brass spark plug insert. My question is is there supposed to be a resistor in there? i just used a piece of copper wire as a temp fix and lo and behold it fired up and took a long time to clear the long accumulated un-burnt fuel.

Thanks for reading

Mike

[tom203]

Yes, the stock plug caps have a resistor in them, probably around 5 kohms in theory. The plug wire itself is copper. Forgo a 12 pack and spring for 4 new plug caps,maybe $20 a set.Cut back each plug wire about 1/4inch to get fresh copper for cap to screw into.

[koolaid_kid]

Best solution is a set of resistive Dynatek wires that do not need the caps. Price is also around $20, and you never need to worry about the caps again.

[TheBlarginator]

Thanks for the replies haha..the 12 pack was a local microbrew and was because the guy I bought the bike off of delivered the bike to my house and wanted some. So some ngk 5k ohm spark plug caps would work perfect correct? What is the reasoning for using the resistors? All I know is that it has something to do with the electronic ignition.

[eil]

What is the reasoning for using the resistors?

Mostly they prevent the high-voltage side of the ignition system from polluting the RF spectrum with all manner of garbage. In the GS's heyday, this mostly meant not interfering with the signal quality of people's television sets and A.M. radios and in particular not ****ing off your ham radio neighbor across the street. Today, it means not cutting off your own cell phone signal and allowing the use of modern electronics near the bike.

On my 850, the resistors in my stock plug caps were toast so I replaced them with some screws that I cut the heads off of. Then a few weeks later I was surprised to learn that my digital multimeter and infrared thermometer would go all haywire if brought anywhere near the bike while it running. Thought about it for a bit, and then switched for the plugs to ones that had the resistors built-in and problem solved.

There is a myth that removing the resistors results in a better spark from the plugs, but it is only a myth.