Subject: Before & After; a dissertation
Author: Tom Bowes
Date: Jun 6, 2004, 7:54 PM
Post ID: 1716917759
OK, so this is not specifically loop related, but let me state for the
record that there certain modifications that nearly every Guzzi should
have.
I was over to Gary Cheek's place, on my V-50III the other night, when he
commented on how dim and yellow the headlamp looked. I had to agree that
the thing was none-too-impressive in the lighting department, but I had
been procrastinating in doing something that I should have done three
years ago when I bought the bike.....install headlight relays. I finally
summoned the ambition to have a motorcycle maintenance afternoon after
church today, and installed the relays and took care of a couple of
other minor electrical problems. What follows is a summary of the before
and after results of my electrical efforts.
Prior to installing the relays and separate feed to the headlight shell
the voltages in the system were as follows (as measured with a Fluke 78
multimeter):
Battery Voltage, no load; 12.8 Volts
Battery Voltage, ignition and low beam on; 12.6 Volts
Voltage at lamp terminals, low beam, stock wiring; 10.05V
Voltage at lamp terminals, high beam, stock wiring; 9.8V
Voltage drop on negative wiring between headlight and battery; .4V
Voltage drop on positive wiring between headlight and battery; 2.1V on
low, 2.28V on high
All in all, a pretty pathetic showing for a bike with only 5000 miles
and standard Guzzi-issue electrical components. I might add that I found
similar stats on my 2001 Cal Special before I reworked the lighting
circuits a couple of years ago. Not to burst anyone's bubble here, but
there is an inherent design flaw in the way that Guzzi has implemented
the wiring on their bikes for too many years now. First of all, the
gauge of the wiring used for some of the loads on the bike is just too
small. Secondly, the habit of running most of the current for the bike
throught the ignition switch is an invitation to a time delayed failure.
Stop and think about how the average Guzzi is wired. The current starts
at the battery, goes up to the key switch, back down to the fuse block,
back up to the light switch, back down to the wiring harness, and back
up to the headlight. Not only do you have the resistance of the wiring,
all of the current has to go through the key switch. Big deal you say?
Big bad deal, says I! How many times have you met a fellow Guzzi owner,
usually with an older bike who complains that their bike won't start
when it's hot? Sure it starts great in the morning when its dead cold,
but take it for a long ride and the bloody thing won't start. The
starter solenoid clicks, sometimes, but doesn't have the ooomph to turn
the bike over. Do ya' know what the problem is? Starting relay? Nope!
Solenoid? Nope! Starter? Nope! Bad cable connection between the battery
and the starter? Nope! Bad ground cable connection? Nope! Vapor lock?
Nope (well maybe).
Guys, it's the key switch, and here's why. As the bike ages (and
sometimes this occurs after but a short period of time) the contacts in
the ignition switch start to get a bit worn and don't connect like they
do when the bike is fresh and new. A bit of corrosion, pitting, or crud
in the switch is all it takes to start the chain reaction. Because the
vast majority of current for the bike runs through the switch, heat is
created as the current flows through the dirty and/or pitted contacts.
As the heat increases, the resistance increases, which in turn increases
the voltage drop across the switch. Which all means that when you go to
start the bike and the headlight has been on, and the switch is hot, and
then you try to come up with another 15 amps worth of momentary current
to bring in the starter solenoid (which, by the way, has to go
through.....you guessed it, the switch) the juice just ain't there to
make it happen, captain.
Let me illustrate the point. As I mentioned above, my bike had 9.8 out
of a possible 12.6 volts at the terminals of the lamp when the high beam
was on. This means that I only had 77% of the available battery voltage
going to the lamp. But what this also means is that the lamp was only
putting out 60% of its rated wattage due to the reduction in voltage.
Why, because as the voltage decreases, the current also decreases
proportionately. Since Watts are equal to Amps times Volts, if I only
have 77% of the voltage and hence 77% of the amperage, multiply them
together and you get about 60%. Consequently, my 55 watt headlamp was
only putting out about 33 watts. Hmmmm....kinda explains that
schoolbus-yellow hue the thing was making. So where did the voltage go?
It was eaten up by the wiring and the switch and transmogrified into
good old-fashioned heat!
Ok, so I ran two #14AWG conductors (one +, one -) from the battery to
the headlight shell and installed two 40 amp "ice cube" automotive
relays in the shell, and a fuse at the battery. The result:
Voltage at lamp terminals; low 12.35V, high 12.30V. Voltage drop on
negative wiring, .080V. On positive wiring, .115V. Available voltage %
at lamp terminals; 98%. Lamp wattage; 96% of 55 watts = 53 watts.
The moral of the story. All Guzzis should be retrofitted with headlamp
relays, and the feed for the starter solenoid relay should be fed
directly from the battery (through a 20+ amp fuse). These two changes
would provide for significant increases in safety, due to better
lighting, and would also markedly reduce "alleged dead starter
syndrome".
Your honor, I rest my case.
Tom
Shelby Township, MI
Early '70 Ambo
1980 G5
1982 V50III
2001 Cal Special