1998 ST2 Biennial Electrical Gremlin

[triangleforge]

Apparently, some force in the universe heard me tell a friend - just one, I swear - that I thought I finally had the ST2's electrical issues under control. Apparently that force has a very petty sense of humor.

Riding on Saturday, I noticed the voltage at the battery steadily dropping - from the 14.0-14.2 where it usually runs (on the low side, but within all the specs I've seen, and apparently plenty to run the bike & charge the battery) all the way down to 12.4 by the time I got home. The bike's computer apparently starts to do funky things at voltages below 12.2. Ignition off, the voltmeter said the battery (Shorai) was at 12.4 or less and when I went out to put a charger on it the next morning it was down below 2.0. I put the charger on it and hoped for the best, and it seems to be holding a charge at right about the 13.2v level it always has.

Modifications/repairs I've done to the charging system over the years include:

• re-positioning the regulator to an aluminum plate mounted on the bottom of the lower triple, between the fork legs and out in the wind
• replacing the regulator twice (once with a Honda unit, currently with one from Rick's Electrics)
• replacing a burned out stator
• replacing the battery with a Shorai, moving it to under the seat and significantly up-sizing the wiring in the starting & much of the charging circuits

Checks I've done so far:

• looked over all the connectors - stator to regulator, regulator to charging system, battery terminals - and don't see any obviously burned or corroded. While they were off, I cleaned & dielectric greased them.
  
• put the meter on the stator output with the motor off; resistance across the two wire output is within spec at 0.3 Ohms -- according to my Haynes manual & LT Snyder's manual, spec is from 0.2-0.4 ohms.
• checked to see if the stator is shorting to ground - it's not.
• measured AC voltage coming out of the stator at a whopping 70 vac at around 5,000 rpm; higher than I expected

Here are my questions:

• What other checks should I be doing (particularly of the regulator/rectifier)?
  I expect the failure mode of a regulator to result in voltage that's too high, not too low; am I missing something?
• if it is the R/R, does anyone have experience or opinions on going with a MOSFET regulator like the ones sold at http://www.roadstercycle.com/?
  

Thanks!

[Howie]

Sounds like you fried another regulator.  Is your '98 a single phase charging system?  If so, a contributing cause could be a clogged gas filter.  The single phase units had two windings, one for running the engine and one for everything else.  This worked OK until fuel injection.  Filter clogs, the fuel pump wants more amps, system works overtime.

You should also check that the regulator has a good ground. 

IMO, the Shorai is a great battery for a canyon carver, track or occasionally used bike, otherwise my preference is for AGM. A fully charged conventional lead acid battery is 12.8 volts verses 14.34 for a Shorai   http://shoraipower.com/lfxcheck   Also, according to their chart that battery is not reaching full charge.  Give them a call, their customer service seems to be quite good.

[ducpainter]

I agree with howie...

except my preference is lead acid batteries for the street.

[triangleforge]

Thanks! As Howie noted, this is a two-phase system; they went to three-phase in 1999. I'd heard about the fuel filter issue - I'll take a look, as it's about time to replace the filter and all the hoses inside the tank anyway.

I went with the Shorai primarily to get the battery relocated under the seat - on this bike, removing/replacing the fairings is a pretty hair pulling/loud cursing experience, so I wanted it in a place where I could easily get at it. Still, I'm not morally opposed to putting it back where it was originally (which I'd have to do to go back to lead or AGM).

I'll get in touch with Shorai as well.

[d3vi@nt]

...on this bike, removing/replacing the fairings is a pretty hair pulling/loud cursing experience...

If you haven't seen this setup before, it might be worth a look: http://www.desmotimes.com/product23.htm

[stonemaster]

+1 on the battery advice, went through some issues with a LI battery, that being said the Shorai is a decent unit compared to others