Resistor plugs and caps.

Mart UK · Oct 30, 2023

I have a boyer and don't believe I have resistor leads. Non resister plugs. I'm unable to check voltage on the bike, the meter goes all over the range. But, runs fine otherwise.

marshg246 · Oct 30, 2023

Mart UK said:
I have a boyer and don't believe I have resistor leads. Non resister plugs. I'm unable to check voltage on the bike, the meter goes all over the range. But, runs fine otherwise.

AFAIK, all out EIs will "usually" work fine without the resistors but the manufacturers cannot live with "usually". Also, the early Boyers and RITAs are more or less electronic points using no sophisticated digital electronics.

I tell people all the time, digital meters have no place in the automotive world and especially in old bikes. An inexpensive analog meter is MUCH easier to use and is not noticeably affected by noise. My favorite meter for motorcycles cost me $2.99 and has a 15v DC range among others. My fancy analog meter cost me less than $30 but the closest DC range without going under is 50v (today they are about $40)

https://www.amazon.com/gp/aw/d/B07S9YB63Y/?_encoding=UTF8&pd_rd_plhdr=t&aaxitk=1452ab98bf8215c4fda7b880afba42a3&hsa_cr_id=1558359350301&qid=1698686899&sr=1-3-9e67e56a-6f64-441f-a281-df67fc737124&ref_=sbx_be_s_sparkle_mcd_asin_2_title&pd_rd_w=oPLId&content-id=amzn1.sym.cd95889f-432f-43a7-8ec8-833616493f4a%3Aamzn1.sym.cd95889f-432f-43a7-8ec8-833616493f4a&pf_rd_p=cd95889f-432f-43a7-8ec8-833616493f4a&pf_rd_r=KCB2ATWP4620G1J4W61M&pd_rd_wg=a2mTt&pd_rd_r=a18abd2e-32f6-40e9-a2b6-6a1d0359a540

L.A.B. · Oct 30, 2023

Mart UK said:
I have a boyer and don't believe I have resistor leads. Non resister plugs. I'm unable to check voltage on the bike, the meter goes all over the range. But, runs fine otherwise.

Boyer Bransden Electronics Ltd

"Why Do I Need To Use Suppressed Plug Caps?*
MKIII and MKIV do not require suppressed plug caps for operation although we recommend using supressed 5000 ohm plug caps. Micro Digital and Micro Power units must be fitted with supressed plug caps. Plug caps fitted with suppression resistors are usually fitted to prevent radio interference. Radio interference (noise) can cause more complex electronic circuits like radios and computers to malfunction.

Our Micro Digital and Micro Power ignition systems contain a small computer operating at high speed that can be adversely affected by radio frequency interference. Symptoms can range from refusal to start to intermittent engine stalling symptoms. Use of non-suppressed plug caps has been known to cause permanent damage to the ignition unit."

*(Or resistor plugs)

Unless there are other sensitive electronics on the bike then suppressed caps/plugs/leads are not required for Boyer Micro-MkIII/MkIV.

Schwany · Oct 30, 2023

Might as well head off topic:

Analog VM I think I got from Radio Shack last century.
I don't know how to use it off the top of my head for anything but measuring voltage. Can't keep much instructional information in my head anymore. Google is my friend.

Resistor plugs are easier to find anywhere that sells automotive spark plugs and they do work on my Norton engine with TriSpark ignition stainless core plug wire and rubber plug boots. I use a modern dual coil with the correct spec. Specs are in the TriSpark instructional manual somewhere. Maybe I'm living in an alternate universe and just visiting. It would explain a lot. lol

stuck amals · Nov 4, 2023

marshg246 said:
The resistors are there to reduce noise. Resistors know nothing of direction of current flow. In a spark plug application, they are a part of a inductance, capacitance, resistance circuit and the high-speed noise is filtered by the additional of a little resistance. That resistance is minor when compared to the resistance of the plug gap and more importantly, non-existent to the current flowing through it to the plug gap.

Noise in the air can trigger various things in a digital circuit but is unlikely to physically damage it. Back current in the coil is high enough to destroy unprotected electronics but the resistance of the secondary has nothing to do with that and the designers of the EIs know to protects against it. Resistor caps/wires/plugs do increase the voltage needed for a spark to jump the gap, but there is plenty of excess voltage available so that's a non-issue.

It has nothing to due with direction. It has to due with the reflected voltage caused by the open gap of the spark plugs. Typical the output impedance of an electrical device only a few ohms of resistance. Most of the of the reflected voltage is dropped Across the 5k resistor.
Maybe the noise people refer to is this reflected voltage.

This noise would need to be of a pretty high voltage level to damage an E.I.

Tornado · Nov 4, 2023

stuck amals said:
It has nothing to due with direction. It has to due with the reflected voltage caused by the open gap of the spark plugs. Typical the output impedance of an electrical device only a few ohms of resistance. Most of the of the reflected voltage is dropped Across the 5k resistor.
Maybe the noise people refer to is this reflected voltage.

This noise would need to be of a pretty high voltage level to damage an E.I.

I believe there is also concern about the RF pulses coming off the HT system, which affect sensitive components via inductive effect. Hall sensors, ignition stator pick up coils, digital circuits etc can be affected by RF pulses if not adequately shielded in some way.

maaseyracer · Nov 4, 2023

marshg246 said:
AFAIK, all out EIs will "usually" work fine without the resistors but the manufacturers cannot live with "usually". Also, the early Boyers and RITAs are more or less electronic points using no sophisticated digital electronics.

Most EI is using hall effect as a low voltage switch and using a transistor to manage the coil switching. The issue is that each time the plug fires, a surge of current flows through your circuit. Because of this there are parts of your circuit that can act as an antenna and radiate that power. The plug wires can help to mitigate the EMI. However, the resistor helps to remove the "peak" of the surge or impulse and preserving the components longer.

Note to the electrical engineers out there, I am sure there are better terms to describe what I am saying here. I have an electricians understanding of electronics and some basic learned experience. Please correct my language and understand if you see fit.

marshg246 · Nov 5, 2023

stuck amals said:
It has nothing to due with direction. It has to due with the reflected voltage caused by the open gap of the spark plugs. Typical the output impedance of an electrical device only a few ohms of resistance. Most of the of the reflected voltage is dropped Across the 5k resistor.
Maybe the noise people refer to is this reflected voltage.

This noise would need to be of a pretty high voltage level to damage an E.I.

Reflected is in the opposite direction and a resistor could not care less. Noise can be in any direction - "riding the wave" or "back current" As I said, unlikely to damage the EI electronics, but it can affect the EI electronics - proven fact. Electronics 101, day one, voltage does not move - it is the "push", not the current.

Resistor plugs and caps.

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