Boyer Ignition and coil compatibility - Triumph Forum: Triumph Rat Motorcycle Forums
Classic, Vintage & Veteran For Coventry and Meriden Models. Anything pre-Hinckley goes.

LinkBack Thread Tools Display Modes
post #1 of 3 (permalink) Old 06-12-2008, 08:06 PM Thread Starter
New Member
Join Date: Jun 2008
Posts: 2
Boyer Ignition and coil compatibility

I have a 76 750 Bonnie that I had put the Boyer Micro power Digital Ignition and their special dual output ignition coil(0008) that came with the kit. Worked great until the control unit shorted out and now malfunctions - I have a second 77 Bonnie with the Boyer Micro - MK III with standard cannister 12v coil marked 3 ohm on it. I took the Micro-MK III off the 77 and put it on the 76 in place of the Micro Power unit that doesn't work and the bike runs fine, but the Micro-Mk III unit gets hot. My question: is the Micro-MK III compatible with the Boyer special dual output ignition coil (coil 0008) on the 76 or will it burn out? The reason I am asking is because I have to buy a replacement Boyer control box and the Micro-MK III is significantly cheaper than the Micro-Power System. I appreciate any input so I only have to buy one unit.
FLYNHI is offline  
Sponsored Links
post #2 of 3 (permalink) Old 06-13-2008, 12:16 AM
Senior Member
Formula Extreme
Main Motorcycle: 77 Bonneville
OzBloke's Avatar
Join Date: Jul 2004
Location: Melbourne, Australia
Posts: 794
The MKIII is rated at max 5 amps for coil switching. Not sure what the current being drawn through the coil 0008 is - if it's a 3 ohm primary winding, then you're basically on the limit, and the MKIII unit will run hot. You could always install a ballast resistor (1ohm, 25W) in series with the coil primary to bring the current (and this heat) down, and shouldn't really affect the spark. It may even reduce the pitting wear on sprak plug electrodes due to over-voltage.

The Micro Digital systems require suppression caps, but also provide a greater range of advance (15deg) at lower revs( 2500) compared to the MKIII (10deg at 5000).

Does the 77 Bonnie have 2 coils, or one 3 ohm coils - your post is a bit confusing on this.

Did the Micro Digital system fail on it's own, or was it an ID Ten T error?

IMHO, I'd go with buying another MKIII, and a ballast resistor. That way, you can swap between bikes if one fails, without any changes except the physical box move (eg no need to re-time), and the ballast resistor will keep the 76 box cooler.

Per Ardua Ad Astra
(Through difficulties to the stars)
OzBloke is offline  
post #3 of 3 (permalink) Old 06-13-2008, 07:26 AM Thread Starter
New Member
Join Date: Jun 2008
Posts: 2

The 77 Bonnie has one 3 ohm coil. The Micro Digital system had a short in its (my) wiring last year and I had some electrical smoke come from under the seat and before I realized it, the Micro Digtal unit actually deformed on the ends from the heat. It continued to work until last week, now it just intermittently puts out a continuous spark - I checked all the cells on the battery, all the wiring including good grounds and found nothing. That is when I took the Micro-MK III off the other bike and installed in on the 76 and it ran fine. So, I deduced the problem is the actual Boyer Micro Digital unit.

Your idea of a a 1ohn, 25 watt ballast resister in series with the coil primary sounds like the solution - I assume I can buy that at radio shack. That way I will buy a second MKIII for about a $100 less and be able to swap them. Thank you for all your help
FLYNHI is offline  
Sponsored Links

Quick Reply
All posts must adhere to Forum Rules

Register Now

In order to be able to post messages on the Triumph Forum: Triumph Rat Motorcycle Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter your valid email address, that can receive an automated confirmation message. Otherwise, you won't be able to gain full access.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode

Similar Threads
Thread Thread Starter Forum Replies Last Post
Coil Compatibility HunterThompson Hinckley Classic Triples 5 07-17-2007 04:08 PM
Boyer Ignition Troubleshoot dagboy Air Cooled Twins Technical Talk 1 10-02-2006 01:52 AM
Boyer Ignition Klicker Classic, Vintage & Veteran 2 08-06-2006 04:59 PM
coil preferences with Boyer HOPOIL Classic, Vintage & Veteran 9 07-14-2005 09:57 AM
boyer ignition help please Classic, Vintage & Veteran 3 04-25-2003 02:54 AM

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are On

For the best viewing experience please update your browser to Google Chrome