1993 vfr750 - eletrical fire / melted wiring

i have recently purchased a vfr750.

the whole way riding it home, i could smell electrics burning,
i just put it down to the factorys around..

the previous owner said it ran flat on short trips, and to get a trickle charger.
there was wiring for one present. it had a new battery.

lost enough charge to start, so i push started it, went for a freeway run,
got off the freeway and it died. push started again, got 1klm before it died,
next time i got 500 meters.

a bike shop had a quick look, and there was a melted mess of wires and plastic
that had clearly been on fire at some stage.

they removed the standard type socket clip and put on a couple of crimped wire
connectors.

i noticed when the rectifier was removed, it had 'cbr900' written on it,
the guy told me it was fine.. but what i meant was, its obviously been replaced.

so now wired back up, 15min battery charge and its at full power.
starts and charges like it should. voltage all good...

but i notice the temp guage is sitting around half way, and it usually hardly moves.

i feel the frame and its hot, real hot.. get home (only 3k's) and check the wiring,

the crimped bits have heat shrunk themselves to the wires, some of the wiring has
turned a bit soft and show burn marks and one with a hole melted in it.

what could cause this issue?

im guessing its not the rectifier.

i seem to always get caught out buying bikes with hidden problems. any info appreciated.

 

Rectifier failure is very common on older VFR's so it's really not a big deal to see a non-OEM unit on a VFR. In addition to the problems with the rectifier itself the wiring harness itself is prone to melting and/or burning due to inadequate wiring being used by Honda. It's best to swap out the entire harness with an aftermarket harness that uses heavier gauge wiring which creates less electrical resistance. As for the heat issue, I've owned two 3rd Gen VFR's and both of mine displayed these similar hot symptoms especially on the right side of the bike. Almost everyone else I talked to who owns the same generation VFR has told me of the annoying heat issue same so I assume it's an issue with all bikes of this generation. It's very annoying but manageable.

Rollin

 

i know it might be annoying but its definitely not managable when it cooks the wires in a 3 minute ride after fixing the problem.

the temp gauge is now reading way higher than it should be. the bike never ran like
that even when it was cooking the connector or whatever.

the connector socket from the regulator was toast, a golf ball sized burnt chunk of
plastic and wires.

was crimped and had the heat shrink thinks, witch shrunk themselves already.

is it possible i cooked the regulator myself? apparently the bike hasnt been ridden
much over 4,000rpm. now, in the 150klm's i've put on it, half the time is high rpm.

but i do think theres more to the issue, and maybe it was a quick fix to sell the bike?

there has to be a regulator that does not produce much/any heat.

the regulator was apparently working, as was the alternator, battery everything fine.

except the wires catching fire.

i would re-wire it if i could, but i cant afford it. have to find the problem and fix it.

 

it is a bit weird how it seems to have suffered the most heat damage just after
the crimped connections tho..

 

Is the radiator full when the engine is cold? Does the solution look clear and not cloudy? The temp gauge can read hot if the green ground on the right side under the top of the fairing is not connected well. It happened to my bike and I got a bit excited until I realized it. The frame on my bike runs too hot to rest a hand on.

BTW you have had good info on the regulator rectifier.

 

My third Generation bikes frame gets so HOT that if you stuck your willy on it, you would be out of action to boink the Misses and might even end up in the ER. Matter of fact the entire bike is a heat sink. Everything from your master cylinder cover to the foot peg brackets.

Side Note: when my r/r finally cooked itself out, it shit black stuff on the frame under the tail section. Had to use carbi cleaner to get the crud off! Get another r/r and make sure your plugs are good. Stator may be bad. There are tests that you can do to check AC from it. Get a manual (Honda) not some crappy Clymers or Heines. Cheers mate Dont give up on her bones.

 

A sliding electrical contact will eventually fail and should be avoided.

The stator produces a 3-phase alternating voltage and current that travels to the rectifier in the 3 yellow wires. If one of the legs of the 3-phase AC circuit is opened up for some reason, the current will arc thru whatever path it can create to find a return path back to the stator. The crimp terminals are tin-coated copper which lose their spring temper when heated. The loss of spring tension allows the contact sliding surface to progressively open due to vibration and arc-erosion. Once the arcing starts then it feeds on itself--heats up and loosens the contact, which creates more arcing, more heating, higher resistance in the contact, etc.

here's one that i caught and if you zoom in on the contacts you can see the erosion traces in the blade due to the arcing at the terminal. The heat damage is greatest at the terminals and progresses up the wiring harness. If the heat gets high enough it will melt the yellow wires and the green wire that is bundled with it in the harness. The loss of the green wire opens up the ground side of the main 12 volt battery bus, and there is no telling where the arcing will occur as the bus currents are trying to find a path to ground.

And that rectumfier was still good and working properly--the sliding contacts were the root cause and culprit.

 

thanks for the pics kb thats similar to my original problem.

the regulator fitted is off a CBR900, and the socket is not on the reg itself,
the wires came out approx 4in long then there was a socket.
it was the socket that seemed to suffer the most damage. it literally was a ball of burnt plastic
and wires that had to be cut out, the wiring was burnt to toast for about 5in
on the other alternator side, but only for about 1in on the regulator side of the connector.

i think its currently got 2 sections with crimped pins, that would be a double
resistance factor and make sens why its cooking just before the first crimped section.

its dark outside but i'll post a pic if i can get one.

i have pushed it pretty hard and temps did not get anywhere near half way.
soon as it was 'fixed' it shot up to over half way from 2min of idle.