Saturday, March 9, 2013 I had an opportunity to meet a friend for dinner and since it was a relatively warm day (in the 40’s), and no precipitation in the forecast, I decided to ride the 2008 Bonneville the 85 mile, 1.5 hour trip around the bottom of Lake Michigan to Journeyman Distillery in Three Oaks, Michigan. The trip started out fine, but at one point when I pulled up to a stop light the engine died. It re-started just fine, so I thought nothing more of it.


50 miles into the trip while on I-90 toward Detroit, I felt some hesitation when accelerating. I also started watching my charging LED monitor light ( that tells me when my battery is charging. I realized that it was not charging normally.

I then experienced a sudden and total loss of power. It was like someone had hit the kill switch while going 80 miles and hour. There was no response from the throttle. I pulled in the clutch and the engine was dead. The starter would turn the engine over, but it would not start. So, since I was in the left lane and there was traffic to my right, I coasted to the center of the highway and parked near the concrete dividing barrier wall.


At this point I checked to make sure all ignition wires were intact, gas in the tank, no leaks, fuses OK, etc. Everything seemed to be in order. I had battery power for lights and signals, and enough to even turn the engine over… just no spark-no start. I figured that one of the main electrical components had failed… coil, wires, plugs, etc.


The Fix

At home, I put the bike up on the jack and removed the seat, tank and side covers. I checked over everything again and could find nothing obviously wrong. I got our my Haynes manual and read through the troubleshooting steps. At the end I read about the ignition control unit possibly failing. I went online and started  searching “bonneville ignition control unit” and discovered there were many posts by Triumph owners with similar experiences to mine. After reading through the various options to fix the problem I decided to try the Procom, Programmable Hi-Performance CDI product available from NewBonneville.


Procom unit mounted under seat with the USB and selector switch shown.


Programming the Procom

Within the next day or so, I loaded the Procom software on a PC laptop (I was irritated and disappointed that there was no Mac version), and used the Procom software to reprogram the CDI unit with Map #9: “designed for advanced riders on general modified machine.” It is possible to edit the settings for each map, but I left it stock for now, and am testing it out on the road.

Here is a complete listing of the maps that come with the Procom software:

  • Map 0 is default and designed for beginning riders on stock machine.
  • Map 1 is designed for medium-level riders on stock machine.
  • Map 2 is designed for advanced riders on stock machine.
  • Map 3 is designed for beginning riders on minor modified machine.
  • Map 4 is designed for medium-level riders on minor modified machine.
  • Map 5 is designed for advanced riders on minor modified machine.
  • Map 6 is designed for beginning riders on general modified machine.
  • Map 7 is designed for medium-level riders on general modified machine.
  • Map 8 is designed for advanced riders on general modified machine.
  • Map 9 is designed for riders on aggressively modified machine.


After a few days of riding with the Procom ICU using Map #9, I’ve realized that the bike runs very well above 1,500-2,000 RPM, but it now runs rougher at low RPM’s and stalls easily on idle. It also will not start after sitting overnight in an unheated garage in near-freezing temperatures.

I sent an email to Procom Engineering on March 26, asking for clarification on what map to use for my application. I provided details on the modifications I have made to my Bonneville. It seems that they should provide more details about what constitutes “minor” and “general” modifications as well as “aggressively modified.” I have not heard back from Procom yet. On March 26, 2013, I also reset the Procom to Map #6 thinking that may help, but alas, it would not start this morning.

If I do not hear back from Procom today with some kind of clarification and direction, I will reset the ICU back to the “default” setting (no map), and see if it will run.


First, I’ve still not heard back from Procom Engineering about my map questions – so consumer, let that speak for itself. The unit has been set back to “default.”

I’ve still been having problems starting my Bonneville in colder weather since installing the Procom. In reading through the Triumph Rat forums, I’ve discovered that cold starting is a problem experienced by other Procom users. It also struggles with a rough idle.

I am happy to report that the cold-start condition did improve after I made a shim adjustment on my DynoJet needle setup (2 shims above the C Clip). I will now experiment with the idle mix screws to see if turning them out another quarter turn (to 3.25 turns) my help.

I am also going to install a new coil and spark plug wires within the next few days.


After installing a new Nology coil and NGK spark plug wires, my Bonnie ran about the same. So, I decoded to swap out the Keihin size 40 pilot jets to size 42. Wow! What a difference! I must have been starving the engine below 3000 RPM! Now the Bonnnie just wants to go, go, go, no matter where I am in the RPM range!

My current setup is:

  • Dynojet needles
  • 2 shims each needle (above C clips)
  • Stock Keihin springs (not the Dynojet springs)
  • Keihin size 140 main jets
  • Keihin size 42 pilot jets
  • Slides drilled to 3mm
  • Idle Mixture Thumbscrews (NewBonneville) turned out 2.5 turns
  • Procom CDI Limiter is set to “Default.”

SEP 2, 2014 UPDATE

I just realized that I never updated this post after completing my Mikuni carb modification. With the Bonneville Performance Mikuni Carb Kit installed on my setup, I changed my Procom CDI map to #9 which seems to work the best.

Procom CDI Limiter User Manual v1.1 – PDF

AUG 4, 2018 UPDATE

Since my last post, I’ve upgraded my Bonneville Performance Mikuni Carb Kit from the 42mm size to the 45mm size. I did not change my Procom CDI map (still #9) and it continues to perform very well. I’ve had no failures or issues with the Procom since I installed it.