Colortune lead does not fit in NGK plug caps???

[Chuck78]

I had started tuning my VM26's with a Gunson Colortune (which I found to be an amazing tool to have), but then upgraded to Dynamite 3 ohm coils (Dyna green copies), new plug wires & NGK 5K resistor caps, and a used Dyna-S built from the good parts of two failed Dyna-S's, as I was getting misfiring partially related to a bad OEM plug cap (3.3megaOhms!!!)

Well I leaned the fuel screws out some after the ignition upgrade, and went to put the colortune on.tge special Colortune skinny plug wire extender didnt want to snap into the NGK resistor caps! I sort of got it started in there, not very far, but it seemed to be holding itself in. Trouble starting the bike, then see that there's no spark or flame in that cylinder!

Comparing the NGK plugs' threaded stud to the stud on the colortune, it appears the colortune high tension lead extender's threaded stud is slightly larger and not nicely tapered like the NGK plug's stud is.

So it seems that the colortune is not useable with these caps. has anyone else experience this, or found a solution for this? I would rather tune it with my brand new plug caps than three out of the four old ones, and I don't want to take the plug caps on and off of my wires frequently!

[chuck hahn]

It should..the end is fashioned for either the post plug in like the OEM caps were or the ball looking end like a modern resistor plug is. Sure your caps aren't just a bit tight???

Or maybe wrap the end of the adapter with some wire if its too loose??

[Chuck78]

I believe I just discovered the problem. the NGK plug caps have a deep taper to them at the beginning of the brass terminal socket, and then the socket with the little spring loaded clicker that locks the threaded stud on the plug in place is at the top of the socket/hole after the taper narrows to the plug stud diameter. The colortune lead has a substantially shorter threaded end than what the spark plug has, and does not appear long enough to make it beyond the taper end and into the socket far enough to even lock in one thread. Sorry for lack of better descriptive words.

it does not appear that my colortune high tension lead extension was broken off, but I wonder if Gunson started offering leads with longer threads?

[chuck hahn]

Will a barrel from another plug maybe screw onto the top of the colrtune lead? Its just aluminum and if gentle one may be fitted?? Don't know because ive not had that problem with mine, but throwing ideas in the wind.

[Chuck78]

yes a barrel off of any of my plugs will fit the colortune lead, but the NGK caps are made to run just on the stud, without the barrel threaded on. The thread sizes the same, but the threads on the plug are probably four times as long as the threads on the colortune hi tension lead extension. I might try sanding or filing a little bit off of the high tension lead where it enlarges at the base of the threads between the base of the threads and where the end is crimped on, because I believe that is bottoming out on the taper before the threaded portion has a chance to get deep enough to lock in place.

[chuck hahn]

Well then..maybe a small piece of some small diameter tubing and sleeve over the colortune lead so it long enough to click in to the caps? Places like Hobby lobby have all sorts of real small tubing for model making and stuff.

Take the lead with you and try a few on for fitment?

[Sandy]

Just use the threaded ball end over the end of the colortune lead and use piece of a long screw with right thread and the head cut off as an extension. Assuming the thread goes all the way through the ball end, if I remember correctly they do.

[Chuck78]

Just use the threaded ball end over the end of the colortune lead and use piece of a long screw with right thread and the head cut off as an extension. Assuming the thread goes all the way through the ball end, if I remember correctly they do.

This is precisely what I was going to do if sanding a matching taper to the lead extension didnt work. Use one of my discarded ball ends as a rod coupler, and try chopping the stud off of one of my plug chop plugs to use as an extension!