Ignition Coils and Spark plug cap resistance

Sorry to chime in a year later... Looking to replace the spark plug caps and possibly ignition coils. My Haynes manual states:

Plug cap resistance
UK Models
Cylinders 1 and 4 (5 K ohm)
Cylinders 2 and 3 (5 K ohm)
US models
Cylinders 1 and 4 (5 K ohm)
Cylinders 2 and 3 (10 K ohm)

Considering the spark plugs and ignition coil resistance are consistent across the models, is there any particular reason I should use a 5kohm vs a 10kohm on cylinders 2 and 3?

I have a 1982 XJ650J Maxim (US model)

 

it is an error in the haynes manual


The Ultimate Relay, Switch, Sensor, and Diodes Guide

XJ650 models:

Pick-up coils:
1980-81 XJ650 Maxim and Midnight Maxim: 700 ohms +/- 20% = 560 ohms to 840 ohms acceptable range
1982 XJ650RJ Seca (non-yics engines): 700 ohms +/- 20% = 560 ohms to 840 ohms acceptable range
1982-84 XJ650 Maxim: 650 ohms +/- 20% = 520 ohms to 780 ohms acceptable range
1982 XJ650RJC Seca (yics engine): 650 ohms +/- 20% = 520 ohms to 780 ohms acceptable range
1982-83 XJ650 Turbo: 120 ohms +/- 20% = 96 ohms to 144 ohms acceptable range


Ignition Coils:

Primary side (input from main wiring harness):
2.5 ohms +/- 10% = 2.25 ohms - 2.75 ohms acceptable range

Secondary side (spark plug wires, without their end caps):
11K ohms +/- 20% = 8,800 ohms - 13,200 ohms acceptable range


Spark plug caps:
5K +/- 20% = 4,000 to 6,000 ohms per cap acceptable range

Spark plugs:
0 ohms per plug

 

it is also an error in the 82 supplement factory service manual

 

Right on. Thank you for the clarification.

 

Might be a dumb question, but I checked both coils; on the primary side i'm within range about 2.4 ohms. The secondary side i'm getting nothing, the bike runs like crap but does run. Secondary check i touch one contact to plug contact and the other contact to the coil ground. My meter is an auto ranging Klein MM700....i'm stumped. My bike is 82 Maxim XJ650. I tried resistor plugs awhile back, hoping to get better spark did I wreck something?

 

Check from one plug wire to the other plug wire.

 

Forget watching any other video on u-tube, etc. about how to test dual-lead ignition coils; this is the only one that shows how to properly test both the primary circuit (from the wire harness) and the secondary circuit (the "plug wires" side of the coil).......with the spark plug caps removed. You can ignore the actual readings that he is showing....the specs for XJ bikes are shown below.....but the method that he shows for testing the secondary circuit is the correct procedure:

www.youtube.com/watch?v=I0TKybs6Rnw
(skip to 3:55 for the dual-lead coil)



For all XJ models except XJ700, XJ750-X, and XJ900 models:

Primary (input from TCI): 2.5 ohms +/- 10%
= 2.25 ohms - 2.75 ohms acceptable range

Secondary (output to spark plugs): 11K ohms +/- 20%
= 8,800 ohms - 13,200 ohms acceptable range


For all XJ700 and XJ750-X models:

Primary (input from TCI): 2.7 ohms +/- 10%
= 2.43 ohms - 2.97 ohms acceptable range

Secondary (output to spark plugs): 12K ohms +/- 20%
= 9,600 ohms - 14,400 ohms acceptable range


For all XJ900RK, RL, N, FN, and F models:

Primary (input from TCI): 2.7 ohms +/- 10%
= 2.43 ohms - 2.97 ohms acceptable range

Secondary (output to spark plugs): 13.2K ohms +/- 20%
= 10,560 ohms - 15,840 ohms acceptable range


For all XS1100 models:

Primary (input from TCI): 1.5 ohms +/- 10%
= 1.35 ohms -1.65 ohms acceptable range

Secondary (output to spark plugs): 15K ohms +/- 20%
= 12,000 ohms - 18,000 ohms acceptable range

 

checked out ok

 

I’m in the process of replacing my coils. When I pulled apart the caps today I found that pretty much all four were set up different.

Is there a write up somewhere showing what should be in each cap and what the order is?

Mine have a spring, a tiny brass disc and a white dowel looking thing which I believe is the resistor. My bike is a 1986 yx600 radian.

 

Some plug caps can be taken apart to get to the resistor (which is the "dowel looking thing" that you observed), and some caps (OEM or aftermarket) cannot:

HCP13105 Aftermarket plug cap RESISTOR ELIMINATOR. This solid, zero-resistance, oxygen-free copper rod replaces the original resistor, thus creating a zero-resistance cap that will last "almost forever" at this level of electrical resistance. When using this resistor-eliminator rod, you should also switch from non-resistor spark plugs to resistor plugs to make up the difference in total system resistance. Since you normally replace spark plugs fairly regularly anyway, it can make sense to use a zero-resistance cap and resistor plugs, rather than a 5K resistor cap and zero-resistance plugs. For use in all of the following original style caps:

T-131: used on all XJ550 models on all the inner cylinders (#2 and #3), and on all XJ900 S/SH models on all four cylinders.
T-133: used on all air-cooled XJ650, XJ700, 1981-83 XJ750, XJ750-D, XJ750RL, XJ900 RK, RL, N/FN, and F models, and XJ1100 models on the inner cylinders (#2 and #3).
T-135: used on all XJ550 models on all the outer cylinders (#1 and #4).
T-140: used on all XJ700-X and XJ750-X models on all fours cylinders.


The easy way to tell whether a cap can be taken apart for resistor replacement is to look up inside the cap (the end where the spark plug is fitted) and to see whether the brass fitting that the “stud” of the spark plug fits into has flat-blade screwdriver slots in it. If it does, then that brass fitting can be unscrewed out of the cap (with a very large flat-blade screwdriver) and the resistor lives behind there. If that brass terminal does NOT have screw slots, then it can’t be removed, and the resistor cannot be replaced.


So it all depends on which caps you have……….the original caps were made by Tokia Denso (“TD”) and have their “sizes” cast into the plastic (sizes are the T-133, T-134, T-140 etc. markings).

 

Thank you for your reply Len! Do you (or does anyone) sell something like a rebuild kit for the OEM caps?

So in my OEM spark plug caps I (we all) have:
(1) Terminal that sits on the spark plug, (2) ceramic resistor, (3) small brass washer & (4) spring.

I lost two of the minuscule brass discs when I opened two of the caps, and two of them didn’t have springs.

Thanks again