Testing HT circuit continuity and resistance - Page 13 - Triumph Forum: Triumph Rat Motorcycle Forums
Air Cooled Twins Technical Talk Technical Talk for Hinckley Triumph Twins: Bonneville, Bobber, T100, Speedmaster, America, Thruxton, and Scrambler.


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post #121 of 130 (permalink) Old 04-17-2019, 05:02 AM Thread Starter
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The second picture, 161K, seems to point out to a faulty plug cap or HT cable. The resistance of the cable itself is negligible as they're made of solid copper rather than the stuff used on cars which is a sort of carbon thread with its built-in resistance. Make sure the cap is securely "screwed" onto the cable, twist clockwise until you feel resistance to going any further.

If that cap to cable joint has been loose for a long time it'll be damaged in which case cut off a few mm of the cable until bare, bright copper is exposed and screw the cap onto it.

You should read about 5K Ohms, the resistance of the plug cap is engraved on it, usually 5k, although it'll have a wide tolerance, + or - 10% or so.

The method of measuring the secondary circuit from cap to cap as depicted in the first post is not valid in the case of the 270 twins (America, scrambler, Speedmaster). These use twin coils rather than a single double-ended coil.

Last edited by Forchetto; 04-17-2019 at 05:10 AM.
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post #122 of 130 (permalink) Old 05-11-2019, 07:04 AM
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My son's 2012 Bonneville SE is giving him (and me) fits in not running right. We've been through air and fuel systems, so thinking it's a fire problem with the coil. It won't start at all with a weaker battery, and with a new one it starts but runs weird. If running it idles awful at enrichment circuit off, is OK at the higher RPM of enrichment on, then loses power above 3000-3500 rpm.

He checked the coil resistance and it's apparently failing on the secondary winding. I forget right now what he said he got for values but didn't come even close to what it should measure.

My question is: What's the cheap way out of this?

I don't mean the very least money, rather I mean what good-quality aftermarket coil can I get (and where) that will use the OE spark plug cables? In looking at the Nology one on NewBonneville.com I get totally confused as to whether or not I have to buy new cables along with the "Dual Tower" coil.

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post #123 of 130 (permalink) Old 05-12-2019, 12:33 AM Thread Starter
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Originally Posted by PixMan View Post
I don't mean the very least money, rather I mean what good-quality aftermarket coil can I get (and where) that will use the OE spark plug cables? In looking at the Nology one on NewBonneville.com I get totally confused as to whether or not I have to buy new cables along with the "Dual Tower" coil.
The Nology (or PVL) coils won't fit the EFI models like yours. These have completely different (mechanically and electrically) coils on them. They're Japanese-made and very reliable with hardly any examples going wrong that I can recall.

If you're convinced the resistance readings are wrong (should be: Primary 2.3 Ohms, secondary 22 kilo Ohms) then you could save money by looking for used ones from either Triumph or Honda. Both part numbers and other useful data in this photo of mine:




For comparison this is the coil used on carbed Bonnevilles:

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post #124 of 130 (permalink) Old 05-12-2019, 07:24 AM
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My son says he measured 37Ω on the secondary (output) stage, which indicates almost a dead short in there.

I think this explains why NewBonneville.com sells the Nology dual coil for the EFI bikes but you have to buy the spark plug wires for the carbureted model to be able to use it. I think it's absurd to have two different length spark plug leads on the stock one, but probably because I've never seen it before.

The decision seems to be either we bite the bullet and convert to the Nology setup, or replace the OE coil with the Honda one. We have a Honda dealer within 10 miles, the Triumph dealer is 60 miles or order from Hermey's.
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post #125 of 130 (permalink) Old 05-12-2019, 07:47 AM Thread Starter
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I think it's absurd to have two different length spark plug leads on the stock one, but probably because I've never seen it before.
When I found out I couldn't believe myself. I manufacture electronic stuff and know how convenient it is to standardise as much as possible. They could have compromised on the lengths quite easily.

The joke is the price they charge for the HT leads:

Right hand side cable part number T1291652 at $89.85
Left hand side cable part number T1291650 at $92.77


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post #126 of 130 (permalink) Old 05-12-2019, 08:46 AM
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Quote:
Originally Posted by Forchetto View Post
When I found out I couldn't believe myself. I manufacture electronic stuff and know how convenient it is to standardise as much as possible. They could have compromised on the lengths quite easily.

The joke is the price they charge for the HT leads:

Right hand side cable part number T1291652 at $89.85
Left hand side cable part number T1291650 at $92.77


OMG. This is just ridiculous.

So this bike has something like 23k miles on it, is 7 years old, and was bought used with 14k miles. In terms of reliable operation and cost being roughly equal, is it better to switch the configuration or to simply replace the OE coil with another? I have pored over this thread and can't get a clear indicator of advantages/disadvantages of either.

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post #127 of 130 (permalink) Old 05-12-2019, 11:57 AM
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Done. I bought the Honda 30510-MM8-003 for 1/2 the cost of the Triumph version and about the same price as the Nology/PVL one that would also require new spark plug cables.

Thanks @Forchetto for all the great info and explanations in this thread!
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post #128 of 130 (permalink) Old 06-06-2019, 11:39 AM
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Just tested the coils on my 2015 scrambler and got 19.6 Kohms on the secondary winding for both coils (primary was good). This was measured from the positive terminal on the coil to the cap. The plug wires were 4.98 Kohms and 5.77 Kohms.

Are my coils bad? Haynes manual says they should be 15 Kohms.
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post #129 of 130 (permalink) Old 06-06-2019, 02:00 PM Thread Starter
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Quote:
Originally Posted by Doctor_Bunz View Post
Just tested the coils on my 2015 scrambler and got 19.6 Kohms on the secondary winding for both coils (primary was good). This was measured from the positive terminal on the coil to the cap. The plug wires were 4.98 Kohms and 5.77 Kohms.

Are my coils bad? Haynes manual says they should be 15 Kohms.
If you measure from the positive LT terminal to the end of the plug cap the resistance should be:


Primary winding + secondary winding + in-built cap resistance (5K)

Asuming Haynes have that 15K figure right it sounds OK to me. Wound components like coils have a very wide resistance tolerance, 10 to 15% is not uncommon.
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post #130 of 130 (permalink) Old 06-06-2019, 02:42 PM
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Quote:
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Quote:
Originally Posted by Doctor_Bunz View Post
Just tested the coils on my 2015 scrambler and got 19.6 Kohms on the secondary winding for both coils (primary was good). This was measured from the positive terminal on the coil to the cap. The plug wires were 4.98 Kohms and 5.77 Kohms.

Are my coils bad? Haynes manual says they should be 15 Kohms.
If you measure from the positive LT terminal to the end of the plug cap the resistance should be:


Primary winding + secondary winding + in-built cap resistance (5K)

Asuming Haynes have that 15K figure right it sounds OK to me. Wound components like coils have a very wide resistance tolerance, 10 to 15% is not uncommon.
Thanks Forchetto! I was kinda hoping these would be the problem but I’ll keep searching haha. Can you think of anything other than the cps that would cause the “big gust of wind” hesitation feeling through the rev range? It happens especially at high speeds and the exhaust note sounds kind of “crackle-y” above 2500-3000 if that makes sense. Ttp stage 1.5 mods done and map rubbers replaced. More info if your interested here: https://www.triumphrat.net/#/topics/952662
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