Topic: damn it all to hell!

[migopod]

So finally, after reading all the wonderful advice on my bloody carburetor issues I took a ride this afternoon
and it was wonderful.  The beast leapt into action like a leapy thing and never missed a single ignition stroke
(that I could tell anyhow).

Got it back into the garage and thought "what the hell, i'll throw the trickle charger on it while i have dinner (first time the
GF let me try her cooking after nearly a year and a half*)". 

So after dinner and the Family Guy, we went down for a ride and nothing electrical happens at all.  No headlight,
no idiot lights, no-bloody-thing.  It was about 10:00pm, so i didn't rip too much apart to try to find the problem, but
the battery is really well charged and there's at least good continuity up to the main fuse terminals. 

I checked all the fuses, and none of them were blown, but no juice seems to be getting anywhere after the fuse box.
I'm using the suggested amperage fuses, so i'd be pretty shocked (no pun intended) if I managed to get excessive
current to anything electrically delicate.  Tomorrow i'm planning on yanking the tank off and checking all the stuff
under the tank and inside the headlight bucket, but i'm wondering if anybody has any advice for other possible faults
(rectifier, etc).

Thanks,

          -migopod

* it was actually very good

[Ben]

Even though the fuses are not blown, it still sounds like the main fuse is gone. I have done this a number of times when connecting a charger to the battery without disconnecting it from the bike. Maybe replace the main anyway and give it a shot, also, and hopefull not, 1. the back of the fuse bax may be melted.......... or, the battery is now shot. Try a different battery?

[Dennis]

Thinking more likely a loose connection between the battery and the handlebar switches or a problem with the key switch. These are 30 year old switches we are operating on these machines and they can get a little fussy.

[Trevor from Warragul]

I've had main fuses that look okay, but when you pull them out they come apart...

[Steve F]

I had a similar problem on a '76 750f, and it was the ingntion switch.  Was out riding, stopped briefly and later it wouldn't start, no lights, nothing.  I took apart the ignition switch, and the electrical "button" contacts that are molded in the switch had gotten hot due to corrosion and had melted down into the plastic.  When that happens, the wiper contact no longer makes contact with the molded in buttons.  I was able to fix it, but it should have been replaced.  Also, fuses can "look" ok, but are sometimes melted on the ends where they're gripped by the fuse holder.  As mentioned, try new fuses first.

[migopod]

I actually checked all the fuses for continuity.  I'm going to take the tank and headlight bucket off
today to check the connections, but the ignition switch didn't occur to me.  It should be pretty easy
to probe around in there when the headlight is out of the way.

Thanks again!

[cben750f0]

i had a similar prob, on the F1, and the fuse would be ok, then not, then ok... turned out that the filment solder had melted(? dunno why?).. and it would make contact some times and sometimes not.... it eventually melted the fuse box... much to my horror.... its amazing how much smoke can come out of 30yo melted plastic... thats why i have built a new fuse box using blade type fuses.... peace

[gregk]

Had a similiar problem with my 750.  The fuse looked good but due to corrosion in the holder, the resistance would burn the solder out of the fuse in the ends.
Cleaned up the fuse holder and never had the problem again.

[migopod]

As cheesed as I am that my only just fixed and tuned bike is again needing poking at, i'm very happy
that I can very nearly 100% rule out the carburetors on this problem. 

The only annoyance is that there's always been this competition between wiring and carburetors for which
kind of troubleshooting annoys me more.  I guess at least I won't have to rub my hands with fish to
get rid of the smell of solvent with this one!

[eldar]

But dont you miss the smell?

[057 adnoh]

 put your finger into the back of your ignition switch and push the connector with all the wiring back in !they pop out on the older bikes and every thing is dead as the red wire does not make a complete conection. this can sometimes be a little loose and cause a really annoying missfire. You can pop the black plate out and lightly sand /Dave

[migopod]

I thought i'd go with simple first, and yanked the connector to the ignition switch.  With a little hotwire action it lit right up.
Upon disassembling the switch mechanism i noticed that one of the copper contacts was melted down into the plastic
casing just enough to prevent contact and the rest were pretty generally filthy and oxidized.  I presume i will replace it
come payday, but in the mean time i've been able to replace the contact with some brass rod ground to fit.

At this point, i'd like to say:  This forum is the best, most awesome resource.  You all rock, and mad props to Steve F
for the call.  I saved so much time that I just dipped my hands in carburetor dip and washed them with a can of
kippers.

Thanks again!

[seaweb11]

I chased the same problem on by rebuild this past spring.  Last resort was the switch, and Bingo, it started right up after being all over my shop floor all winter. Nothing says warm and fuzzy like the resounding "click" of a new ignition switch