Chasing Intermittent Tiger Stalling: Checking Motorcycle Electrical Systems

I'm starting to think the stalling issues I'm experiencing on my Triumph Tiger might be an electrical issue.  The onboard computer isn't giving me any error codes, but when I rev it the lights on dash dim a bit, which shouldn't happen.

Motorcycle electrical systems are, like many aspects of motorcycling, a simplified and often more high maintenance version of what you see in a car where the extra space and size means you can make things modular, more self contained and cheaper to rebuild.

Instead of packing everything into an alternator running off the engine via a belt, motorcycles break things up to minimize drag on their smaller engines (belt driven systems suck a log of energy out of a small motor).  A bike will typically put a generator inside the motor on the engine crank so if the motor is turning over the generator is using magnets to generate electricity from the spinning motion.  This produces alternate current but, like cars, bikes generally use direct 12v current, so they need something to change the AC to DC.

Regulator/Rectifiers not only switch your power generation from alternating to direct current but they also regulate it so your battery is receiving a steady 14.5 volts on charge.  A failing reg/rec can overcharge or undercharge your battery.

The flakiness of my situation (sometimes it works, sometimes it doesn't) suggests that this is a connection issue.  Before I start replacing parts I'm going to chase down all the connections, Dremel them clean and refasten everything properly.  If I'm still getting stalls and weird light dimming I'll test components one by one until I've isolated the flakey bit.

I teach computer technology as my day job and a flakey power supply (which also converts wall AC to in-computer DC) can produce some very unusual and difficult to track problems in a computer.  This feels like that.

There is nothing magic about how electricity works, but many people are really jumpy about it.  I've found that a rigorous, step-by-step analysis will usually uncover even the flakiest of electrical failures.  It will again here too.

RESOURCES

Analysing engine stalling in powersports motors 

How to know if your regulator/rectifier is failing

How a motorcycle electrical system works

Various motorcycle charging systems (full wave/half wave)

MOSFET regulator upgrade

The regulator/rectifier (#7) at the top is under the seat next to the battery.  I'm going to remove, clean and reinstall that.  

The big parts on a bike's charging system are astonishingly expensive!  Replacing an alternator with a quality rebuilt parts will cost you about $170CAD.  To do the rotor, stator and regulator/rectifier on the Tiger would cost me the better part of two grand Canadian!  Some of that might be old-Triumph price gouging, but it's ironic that all the online explanations describe motorcycle charging systems as built down to a price when it's clearly built up to one... on a mountain.  But there are options...