Help me with a general bike electric question

[jeffcoslacker]

I'm still working on that old '81 Moto Guzzi V50 Mk III LeMans (long name huh?)

Does anyone know offhand, are most systems wired so that the starter relay (not the solenoid) being energized turns the headlight relay off while the starter is cranking the motor?

Seems like it would be...I'm having an issue with no power to the headlight relay after replacing a defective starter button with an aftermarket universal unit...wondering if I inadvertantly wired it now in a way that is cancelling the headlight relay constantly...

God I hate electrics...

[aussieidiot]

you replaced the starter button only? how many cables were attached to the original and how many contacts on the replacement.

being an 81 vintage it will be easier to trace than a modern bike but Motto Guzzi.........

are the cables color coded?

some relay's run dual contacts. normally open for the device being switched and a secondary set which can be normally closed or normaly open depending on the relay.

there may be a control relay which is normally closed in between the starter relay and the headlight relay. it may be getting constant power to open the contacts thus relieving power from the headlight relay.

[jeffcoslacker]

There are 4 wires from the original switch pod...this contains the engine kill switch and starter button. Near as I could figure, the starter button died.

The quickest way I could think of to do it was to run a switched ground wire and spliced into the starter relay's ground side, so it energizes the relay when you press the new button...it works, but I have no headlight relay power now...since the ground wire I ran is only a complete circuit when the button is pressed, I don't see where I've really changed the original configuation when the button is at rest...

Could be there is another issue that was what smoked the starter button to begin with...as far as I can see, there are only two Bosch automotive-type 5 pin relays...2 pins for the coil power, then power in, and two out...if I understand the little diagram on it correctly...

Since there is really only a need for three wires to the switch pod (power in, out from the kill switch, out from the start switch) it could be the fourth wire has something to do with my problem...

A wiring diagram would be SO helpful at this point...

[richtazz]

here you go Jeff, a wiring schematic!

http://www.thepeanutslab.com/bikehen...wiringpiaa.pdf

a link to a fix for what you're possibly experiencing:

http://www.guzzitech.com/SmallBlockRelay-PHayes.html

and heres the link to the guys main page also, hope this helps you buddy!

http://www.thepeanutslab.com/bikehenge/v50.html

[jeffcoslacker]

Wow that was a nice find, Rich, thanks! i'd heard the small block relay fix mentioned before but didn't know where to find it.

You guys ain't gonna believe this, but there actually was no problem...

I'm used to anything built in the 80's having full time headlights you couldn't turn off if you wanted to...

Turns out this one does have an on/off switch, and her lo beam is burnt out, she's just been using the high beam.

She turned off the headlight while I was working on it, to save the battery. I never even thought to look for a switch that shouldn't even be there ...I guess European bikes were a bit behind in full time lights...

So anyway all is good now. Still gonna keep that schematic...I'm sure I haven't seen the last of this bike...