Spark Plug Caps Discovery

[leonardhcross]

Hello Naked friends. My 76 GL1000 project bike has been going backwards. Over the past two weeks, the bike has gone from running decently for a bike that has been sitting 15 years, to rougher and rougher running and idling. Having rebuilt the carbs, I started by presuming that my issues were related to some blockage in the idle system. I did not want to remove the carbs for a third time so I drained the bowls, syringed in 180 ml.of a 50:50 Seafoam and gas mix. Turned it over a bit with the kill switch on and the choke fully closed. Then let her sit for 24 hours. When I tried to start the bike, it really struggled....coughing, stumbling and some serious backfiring. I noticed that the right muffler was getting warm but not the left. I stopped trying to force her, drained the remaining Seafoam/gas mix and injected straight gas. Then tried her again. Same thing. Chugging, popping and backfiring. However, this time, I was able to pull off plug #4 with no effect. Then, plug #2 which instantly shut the engine down. One more try at running and got her going just enough to pull both #3 and #4 plugs with no effect. I did not even try #1 so that is uncertain. So.....I switched focus to "fire" instead of "fuel". Previously, points had been gapped and static timing set. I have spent the last three days trying to pinpoint the problem. I bench tested the coils and they met specs for both primary and secondary, (I tested the secondary windings with the plug caps off). I installed a dedicated ground on the coil. I tried to service the resistors on in all four plug caps. On some, I could extract the resistor and others, I could not. I had several extra used caps so I worked on those until I had four caps with tested resistors. I reinstalled the caps and replaced the coils. Concluding that the coils were good, I decided to re-check my points and static timing. After three frustrating tries and swapping in other good points, I finally achieved proper gap on both sets with the left set lighting up on F-1 and the right on F-2. I tried again to fire up the bike. No improvement. I tested the secondary wiring again with the coils on the bike. I could get no reading on either left or right coil. Off came the coils again. This time, I was unable to get any reading across the
secondary wiring. Nothing on 1-2 and nothing on 3-4. I pulled off the four plug caps and tested the secondary windings again. Bingo! 14.77 ohms on the left and 14.51 on the right. Then, while I had the caps off, I tested their resistances. On 1 and 2, I could get no reading. On 3, I got 2.9 ohms and on 4, I got what I assume was a decent reading of 4.89 ohms. After all of this, it appears that my problem COULD mostly be old, worn out spark plug caps. I won't know until I purchase and install new caps. Ordered today. This has been a tough, three day process but I am now, at least, encouraged. I will post a follow-up.

IMG_2451.jpg

[pidjones]

Get rid of the resistors ( a piece of copper #10 wire can replace them) and switch to resistor plugs.

[redglbx]

Amen

Couple of other thoughts as well, when you run it again look for sparks or a blue aura around the coils, possible cracks in the coil cases. All things said and done though I’d still bet on a clogged idle circuit. My .02

[leonardhcross]

Get rid of the resistors ( a piece of copper #10 wire can replace them) and switch to resistor plugs.

Thanks pidjones. I like that idea. Currently, inside my caps are a spring, a resistor and a brass cap. I assume that I would replace the spring and resistor with the piece of #10 copper. Because the spring compresses, I don't know how long the piece of #10 copper should be. Can you advise?

[leonardhcross]

Amen

Couple of other thoughts as well, when you run it again look for sparks or a blue aura around the coils, possible cracks in the coil cases. All things said and done though I’d still bet on a clogged idle circuit. My .02

Thanks as always redglbx. I suspect that you are right. But, first I have to get a spark. It is frustrating that a person could do a full carb rebuild carefully and purge the fuel pump before installing the carbs and end up with a blocked idle jet. Do you think that filling the float bowls with 50/50 Seafoam and gas has the potential to open a clogged idle circuit?

[leonardhcross]

Get rid of the resistors ( a piece of copper #10 wire can replace them) and switch to resistor plugs.

Thanks pidjones. I like that idea. Currently, inside my caps are a spring, a resistor and a brass cap. I assume that I would replace the spring and resistor with the piece of #10 copper. Because the spring compresses, I don't know how long the piece of #10 copper should be. Can you advise?

Oh.....and do you think that I should snip off 1/2 inch of each of my wires for a fresh start?

[redglbx]

Leonard, PID sent you down a good path there, I’ve been running that combo for quite a while now, the good thing about it is that you get a fresh set of resistors everytime you change the plugs, much better !

As far as trimming the wires off, I recommend trimming as little as needed because there isn’t a lot of extras and you really can’t change wires because as you know they’re molded into the coils (stupid idea) but if the wires get too short then that becomes the reason to change the coils out to some better piece’s. The oe coils are around 7k output vs Dyna or equivalent at 35k ,,, much better.

On the idle circuit, no just pouring some cleaner in there is not going to clean the circuit unless you have flow in that circuit. And because the idle jet is only 013.5in ( a human hair is around .003-.004in) it will easily plug, once you have some flow through that circuit then it will easily clean out, maybe. Years ago on my 80 CBX I was having trouble with it after rebuilding the carbs, just wouldn’t run well at all. I had bought a lot of parts for it from Tim’s CBX and got to know the owner Tim Ware (great guy) who had taken a real interest in my project and he always said that when you think you have the idle circuit clean go back and clean it again. If you sand a Gumout cleaner plastic straw to a point and spray it in the idle jet (protect your eye’s) it should come out of the idle discharge hole in the carb bore.

One other thing that Tim taught me is that the little springs in the float valve pins can & do fatigue and give up their tension allowing things to flood, my CBX was the first place I found that but I couldn’t believe; it, Tim was so sure that he sent me 6 new valves free of charge to prove that point. The only caveat that he gave me is that I send him a check if it does fix my problem, I had a check in the mail within the week ! I learned a lot from Tim Ware, great guy !

[leonardhcross]

I am still seeking guidance on the length of the #10 copper "filler". Is it just the length of the resistor? Do I continue to use the spring?

[pidjones]

I would keep the spring and make the #10 copper the same length of the resistor it replaced.

[Sidecar Bob]

Forget everything that has been said about removing the resistors from the caps. Replacing the resistor with a piece of wire (or brass rod or brazing rod or brass bolt) is a bodge that is just useful to get it running until the new caps arrive.
AND a less known failure mode is for the link between the contact inside the cap and the point that screws into the wire to fail.
AND the rubber boots that seal the cap to the wire and plug are 40 odd year old rubber....

New XD05F caps are cheap & easy to find so just replace them. You can even get XD05F-R caps made of red plastic (because you know that red parts make the bike faster )

Oh, and as for the moulded in spark plug wires being a stupid idea, that was fine for something expected to last 5-10 years and almost all bike coils were like that in the '70s.
But that said, GL1500 coils aren't terribly inexpensive, work well, have replaceable wires and allow you to delete the ballast resistor. Unless you are going for concours level judging there is no excuse for not replacing the coils & wires to go with those new caps.

[leonardhcross]

Thanks for the input. I have just spent four hours attempting to salvage 12 old spark plug caps. In some, the resistor was corroded inside and could not be ejected. In a couple of others, the resistors came out but their ends were too badly corroded. In some, I was able to fully disassemble the parts, clean the screw and the contact deep inside the cap, flush with brake cleaner, blow out with air, test the resistor and reassemble. And, after all of that, there was still no continuity between the spark plug end and the screw-in end of the cap. It appears that, as Sidecar Bob stated, the "lesser known fail" is between the wire screw and the inside base of the cap. Tomorrow, I am going to dissect a couple of these to see if I can locate the disconnect. I will post a video of the salvage attempt and the dissection soon.

Cleaning inside Caps.jpg

Cleaning Inside Caps #2.jpg

[redglbx]

As Bob stated, any hotrodder worth his salt knows that RED is the fastest color….. period !

As far as the coils go,the 1500 coils are a good inexpensive option due to being able to replace the wires (molding them in is still s stupid idea, imho) and eliminating the ballast resister is a plus as well, but imho the extra power of the Dyna type coils (35k volts vs 7k) is a big plus. Will they make more power ? No ! But it should start better and run cleaner at lower rpm’s but no real noticeable difference at higher rpm’s.

On mine when I removed the cap resistors that ran 4.9k to 20k ohms of resistance and installed the copper grounding wire I measured 0 ohms of resistance. But I measured 5k ohms in the new resistor plugs, so you should get a fresh new resistor every time you change the spark plugs. You do change your spark plugs don’t you ? Anyway that’s what I do at this point in time !

Oh, and change your belts !!!

[Shadowjack]

1200 coils also have removable wires (with cylinder labels ), but they may be less common than 1500s.

[Sidecar Bob]

'83 1100 coils will work too and the wires are replaceable but need the ballast resistor (not sure if 1200 coils do). I had '83 coils with a 1000 engine for 21 years before replacing them with 1500 coils 8 years ago (& changing to an 1100 engine 2 years later).

[leonardhcross]

A brief summation.....After a week of chasing ignition gremlins....setting points, static timing, new ground for coil, pulling coils, (twice), new non-resistor plugs, bench testing everything, and rebuilding plug caps, I fired her up. She started much more easily but continued to idle rough. I pulled off both #3 and #4 plug wires and nothing changed. I was still running only on the front two cylinders!
Thanks to a suggestion by friend and member, Cliff Reynolds, I peeled back the boot to check the bullet connectors for the primary wires. In the process, one of the yellow wires slid out. The connector was clearly weak. I snugged it up a bit with needle-nose pliers and...ta da! Cylinders #3 and #4 came back on-line. I know that all my efforts, particularly on the caps has to have helped but, in the end, mostly all I needed to do was snug up one bullet connector. https://www.youtube.com/watch?v=OFreksy ... u3&index=1