KIds in the Hall Effect

Intermittent problems are the most annoying of all. When a bike won't start, or always pulls to the left or something you have this repeatable event that helps in the diagnosis. When the problem is intermittent you have to be thinking-will this be the ride where I get left stranded?

I had noticed that the problem seemed to occur only on hot days in stop & go traffic. Since the cooling fan and coolant temperature sensor had both been replaced, I was confident the engine wasn't overheating and that the ignition control unit was getting an accurate signal. So I'm really looking for something that gets flaky at higher temperatures. That tends to be electronic goodies. Maybe my ignition control unit is going bad.

I did some reading on the ignition control system and posted a question on a forum. The problem description led some of the more experienced wrenches online to the hall effect sensor. This is basically a timing switch that sends out a signal when a metallic element enters its path.  Apparently they crap out at high temperatures after a while, acting up like mine did , when they are in their death throes.

The diagnostic test for a intermittent failure of a hall effect sensor (HES) is to let the bike cool down, start it and see if it idles normal. Then you point a blow dryer at the T-shaped section in the front of the engine that houses the HES. If the HES cuts out when the blow dryer gets it up near 150-160 degrees F, then you have your culprit.  In my case, it went from the smooth idle to the chugging death spiral in minutes. I couldn't even get it to restart. After I let it cool 20 minutes it started right up again. We're onto something here!

Then I went to the Euro Motoelectrics site to see how much a new one cost. HOLY CRAP! They want $400 for a new one?  That would eat up my 20% budget pretty fast.  I scoured the forums for some options and found that I could get a working replacement on Ebay for $100, or I could get replacement sensors for about $40. So I decided to do both. I would have a direct replacement assembly that is plug and play, and I would have the components to rebuild my old one as a spare.

The new HES unit arrived in a few days and it was pretty easy to replace. Pop off the gas tank, remove the electrical connector, snip a couple zip ties and then remove some bolts from the T-shaped HES cover. I carefully marked the location of the base plate notches relative to the notch in the HES housing so I could get close to the original timing.

So I swapped out the unit, bolted the cover back on and it started right up again. Took it for a ride around the neighborhood and it felt odd. Throttle response was poor and inconsistent and the bike stalled at the top of the hill. I managed to restart it, ride it back home and started scratching my head again. Crap-tastic!