Resistor Vs. Non-Resistor Plugs

Jim

Jim

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So this'll take a minute to 'splain...

Yesterday I was putterin' around the 'hood on my SG. Pulled up to a stop sign and she went to running rough at idle. Rev it a bit and she clears up, but went right back to rough soon as it drops back to idle. Headed for the barn... stalled it a few times starting out, but made it home. Pulled the plugs and they were black as coal. Let me note here that I'm running the non-resistor caps (LZFH) so I can run the more common BPR7ES resistor plugs. And a further note... the rich running is most likely 'cause I went to a stock Special exhaust with holes drilled in the end caps, and haven't rejetted. Looks like I'll need to drop the pilots a number. Anyway...

Didn't have any fresh resistor plugs so I stuck a set of BP7ES non-resistor plugs in just to see if it cleared up the idle miss. It did... back to smooth idle. So... figured I'd run the straight caps and plugs until I could clean up a fresh set of resistors. With me so far? NO ADDITIONAL resistance in the coil secondary.

Went out again this afternoon for a quick ride. Engine runs good other than a tad rich... which I've know about since swapping exhausts. Get up to the corner, right turn signal... and it doesn't flash... it's on solid. Tried the left and it gives superfast flashes... like two flashes per second fast. Back to right and solid. About then I finally notice my voltmeter. It's flashing 88.8 to beat the band..... Wtf?? Anyway, pressed on and did a big lazy loop around the sleepy town of Gladstone and headed for the barn, using hand signals.

Back home I shut the bike off, turn it back on and the voltmeter reads 12.5-ish... solid. Tried the turns and both worked normally. Started the engine and it all went south again. So.... I've been into the headlight bucket and under the seat adding the fog lights... fuck, where to start? So I'm a little slow today, but the light bulb over my head finally lit up. Took the old resistor plugs down to the bead blaster, then brake cleaner and shop air.... stuck 'em back in and everything works as it should... no gremlins. Stuck the non-resistor plugs back in and it all went haywire again. Sumbich.

So anyway... the question's been asked here before: What happens if you run a straight secondary with no resistance in the plugs, wires and caps? I have an answer for y'all now.... weird shit. :er:
 
Last edited:
Jim said:
So anyway... the question's been asked here before: What happens if you run a straight secondary with no resistance in the plugs, wires and caps? I have an answer for y'all now.... weird shit. :er:
Click to expand...

That is weird! I know that I ran resister caps and resister plugs together accidentally for about a year before I realized what I had done, and it had no effect at all. :shrug:
 
Watching the threads regarding resistor/ non-resistor plugs and caps I got to wondering what I had done in running Autolite plugs, 65 in the left cylinder and 64 in the right. The 64 has the removable top, the 65 doesn't. To run the 65 with the stock NGK caps required grinding the top of the plug to fit. Eh...I did that on my old '83 . It worked but seemed sketchy. On the '77 I went with caps that take the bulb top.
I don't know if the plugs and caps are resistor or non resistor as I've slept since then and threw the boxes they came in out ......but I know a blind pig can find an acorn and the Autolites are available and affordable.
 
5twins said:
I know you can run no resistance in a points system, I did it for several years. I guess you can't with an electronic ignition it seems.
Click to expand...
I think it's gonna come down to each individual bike. Lot's of wild cards on this (and any) bike... such as mounting the MP08 coil back on the battery box and having the HT leads go forward from there. Dunno.... guessin' it'll come down to each bike/ignition system. Be curious to see if anyone else has had screwy stuff from different resistance combo's?
 
I’ve Only ran Pre-80 stock points systems (many now) which seem to run the same whether resistance or not .
I do run solid copper wires, LZFH non resistor caps , BP7ES non resistor in hopes of the most healthy spark.
Only once did I experience strange electrical symptoms , but that was because of a UFO passing over head
🛸
 
WideAWAKE said:
Jim - have you got another set of non resistor plugs to see if it does the same thing? Double confirmation that maybe the plugs weren’t weird.
Click to expand...
I'm sure I do somewhere in this mess. Soon as I run across a set, I'll give it a try. Be curious to see what happens...
 
That's an interesting thread. I have new non-resistor NGK plugs and caps on my XS650D. I was wondering if I needed to change to a resistor plug or cap (stock points fitted) but it seems I don't need to worry.

Certainly back in the 1970's, none of us had the faintest clue about different resistances on parts. If it fitted, we used it. The only thing we worried about back then was not using a too hot plug that damaged pistons.
 
I have always believed that the resistance in the circuit was for radio interference suppression.
Mark Whitebook of Probe Ignitions advised using some resistance in the coil secondary (plug or cap) to minimise noise entering the trigger circuit.
The 5K resistor caps over time increase in resistance, and I was advised by the local Ignitech supplier to use resistance plugs in favour of resistance caps due to the plugs having a more stable resistance over their life.
 
Signal said:
I have always believed that the resistance in the circuit was for radio interference suppression.
Mark Whitebook of Probe Ignitions advised using some resistance in the coil secondary (plug or cap) to minimise noise entering the trigger circuit.
The 5K resistor caps over time increase in resistance, and I was advised by the local Ignitech supplier to use resistance plugs in favour of resistance caps due to the plugs having a more stable resistance over their life.
Click to expand...
RF suppression would be my understanding too. Metal clad plug caps used to be very common too for the same reason. I don't have any understanding of electronic ignition system requirements. But I can easily understand why they might have different requirements to a set of points.
 
RFI couples to many low current circuits via the air or close circuit.

That's why I cannot use most of my t/c meters when running.

That's why some speed-hut tachs go haywire.

cliff
 
Mailman said:
That is weird! I know that I ran resister caps and resister plugs together accidentally for about a year before I realized what I had done, and it had no effect at all. :shrug:
Click to expand...
"This sale is for one piece 4' long of brand new 7 mm Black inductive core wire wound silicone cable USA Spark Plug Wire as pictured. This pricing is sold by the foot, if you need 8 continuous feet then choose 2 and so on up to 1000. This is the correct wire to use when you have an electronic ignition. This creates the resistance needed to reduce radio interference so your ignitions wont cause your ignition to fail. If you use this wire you wont need the 3000 ohm resistive cap. I measured an estimated 15.0 M OHM per foot on this cable."

This e-bay seller is claiming his wires are 15 M ohms per foot. So too much resistince may not be a problem. On a V8 engine, some wires may be 1' and others 3' long. So a mix of 15M ohm and 45M ohm on the same engine.
 
Jim said:
So this'll take a minute to 'splain...

Yesterday I was putterin' around the 'hood on my SG. Pulled up to a stop sign and she went to running rough at idle. Rev it a bit and she clears up, but went right back to rough soon as it drops back to idle. Headed for the barn... stalled it a few times starting out, but made it home. Pulled the plugs and they were black as coal. Let me note here that I'm running the non-resistor caps (LZFH) so I can run the more common BPR7ES resistor plugs. And a further note... the rich running is most likely 'cause I went to a stock Special exhaust with holes drilled in the end caps, and haven't rejetted. Looks like I'll need to drop the pilots a number. Anyway...

Didn't have any fresh resistor plugs so I stuck a set of BP7ES non-resistor plugs in just to see if it cleared up the idle miss. It did... back to smooth idle. So... figured I'd run the straight caps and plugs until I could clean up a fresh set of resistors. With me so far? NO ADDITIONAL resistance in the coil secondary.

Went out again this afternoon for a quick ride. Engine runs good other than a tad rich... which I've know about since swapping exhausts. Get up to the corner, right turn signal... and it doesn't flash... it's on solid. Tried the left and it gives superfast flashes... like two flashes per second fast. Back to right and solid. About then I finally notice my voltmeter. It's flashing 88.8 to beat the band..... Wtf?? Anyway, pressed on and did a big lazy loop around the sleepy town of Gladstone and headed for the barn, using hand signals.

Back home I shut the bike off, turn it back on and the voltmeter reads 12.5-ish... solid. Tried the turns and both worked normally. Started the engine and it all went south again. So.... I've been into the headlight bucket and under the seat adding the fog lights... fuck, where to start? So I'm a little slow today, but the light bulb over my head finally lit up. Took the old resistor plugs down to the bead blaster, then brake cleaner and shop air.... stuck 'em back in and everything works as it should... no gremlins. Stuck the non-resistor plugs back in and it all went haywire again. Sumbich.

So anyway... the question's been asked here before: What happens if you run a straight secondary with no resistance in the plugs, wires and caps? I have an answer for y'all now.... weird shit. :er:
Click to expand...
I had to search for this to read again and glad I found it before posting the exact question. I’m just about out of resistor plugs and about to get into my non resistor plug stash. I’ll have swap the caps out for sure. Glad I kept a set.
 

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