Topic: What "Electrics" gets ruined when "Reverse Polarity" occurs ??

[750goes]

Guys,

Did not happen to me, but to a prospective bike I was looking at.

1976 Honda CB750F1 - was for sale until yesterday, but did not meet its reserve price - so was passed in at Auction. I talked with the owner during the week to see if it was a possible addition to my small collection, as he stated even though he had owned it for three years - it was running nicely and was ready at that time for being registered, then he bought another two bikes and put this in the garage, where it has sat for a while.

I talked to him this morning - asked if I could come have a look at it (he is about an hour away), he said fine..
Got there and he was all apologetic said he had been trying to call me (do not hear my mobile phone when riding).

He had tried to get the bike started before I arrived, by jump start from another battery - hooked up the jump wires wrongly - got distracted by his other half and then notices smoke coming from under the left sidecover - too late she cried....

Wiring harness around the regulator & rectifier looks pretty nasty. Looks like one or two wires have had the plastic melted off for several inches.

Question:
What could possibly/probably be stuffed if this happened - what do I need to check/replace, as I could still be interested - but need to assess and cost out the damage before I get back to the owner with an offer.


thanks for your replies in advance

 

[Gordon]

The rectifier is fried.  As for the wiring, it depends on how long the polarity was reversed.  The only way to tell the extent of the wiring damage is to open up the harness and follow the melted wires. 

[750goes]

If I said 5 minutes - what damage would you think then ?

be honest with me Gordon - I can take it.......

[Gordon]

I'm surprised the bike isn't a smoldering pile of ash at this point.

The only experience I've had with reversing the polarity was on my 550.  That was only for a few seconds, and I had to replace the entire length of ground wire that ran up through the harness and connected to the frame near the coils. 

Since the bike didn't catch fire, the most I can see needing to be done is to replace the wiring harness in addition to the rectifier.  But you may be lucky and only need to replace a few wires in the harness that were melted. 

[mrblasty]

I bought my 750 from a guy who had done this and gave up trying to fix it.  He had laid a raggedy impersonation of a harness on the bike. So it got a new harness because the old one was completly melted, I replaced the rectifier and voltage regulator and fuses, juiced up an old battery and it started with no issues.

[fuzzybutt]

new harness, regulator/rectifier at the least.

[750goes]

Thanks for the replies so far....all good thinking material..

Could it have done any damage to the stator windings or starter motor, coils, ignition switch/ kill switch...I hope the ignition key was not turned on as well, or gone as far as into the headlight bucket wiring..

I presume that most damage would likely have occurred along the ground paths or frame ground wires, taking all the amps etc from the battery connected to it at the time..would melt/overheat those ground wires..??

[fuzzybutt]

i dont think theres any way the starter could have been damage likewise for the solenoid. kill switch, coils (as long as the kill switch wasnt set to run) should also be ok. but like i said. i'd plan on a new harness. i dont see any reason why the parts-n-more harness couldnt be adapted to work with your f1

[mrblasty]

I would think the main fuse would keep the switches and lights safe.  But I 'll be the first to say I'm no expert.

[750goes]

thanks again, I'll have a look at the parts n more harness - do you have a link for it if I can't find it ??

cheers

[TwoTired]

Suspect the rectifier, the wires from both battery posts to the rectifier (Red/white and Green pathways) and all connectors in the path including the plastic housings.  Possibly the wires between rectifier and stator (and their connectors/housings).   Probably not the stator itself.  I don't see why the vreg would be damaged.  All the lighting and other pure resistive elements of the bike don't really care about power polarity.

Could have damaged the battery, jumping from another with reversed polarity.  (Remote chance)

Cheers,

[750goes]

Two Tired,

thanks for the reply - I will be making the owner an offer in the next few days, to see if he is amenable to me taking it from him for a reasonable amount - (less than he was bid for it I hope) and see what happens.

I would guesstimate it will be at least two full days work for me to check everything out - and repair it electrically, plus any component parts that need to be replaced - I have quite a few bits and pieces I seem to have gathered in the last few years..

I think the old battery was already knackered - thus his attempt at jump starting it....

thanks for all the replies so far - will see what happens (probably have to sell a few things to buy this bike though)

 

[Jonesy]

But I 'll be the first to say I'm no expert.

Sorry, MrBlasty.. your title shows "expert", so you're on the hook...

thanks again, I'll have a look at the parts n more harness - do you have a link for it if I can't find it ??

https://www.partsnmore.com/Merchant2/merchant.mvc?Screen=BASK&Store_Code=1&Action=ADPR&Product_Code=24-4001&Attributes=Yes&Quantity=1

[HondaMan]

But I 'll be the first to say I'm no expert.

Sorry, MrBlasty.. your title shows "expert", so you're on the hook...

thanks again, I'll have a look at the parts n more harness - do you have a link for it if I can't find it ??

https://www.partsnmore.com/Merchant2/merchant.mvc?Screen=BASK&Store_Code=1&Action=ADPR&Product_Code=24-4001&Attributes=Yes&Quantity=1

Your avatar is missing the part that says, "But the unique sound and performance is worth it!"   

[Jerry Rxman Griffin aka MuthaF'er]

I'd use this as a good reason he should sell cheap. Ask him to repair it first OR to at least check into finding and purchasing the parts once he finds all the problems. If he has to have someone else do the work he's going to find out the cost will be half of what his bike is worth IF he can find the parts.

New replacement harnesses are just not available for our bike and used ones are difficult to come by. You can always attempt to repair the harness but I'd say if it was 5 minutes you might be better off trying to find a good used harness. I'll agree that the other part you'll need to replace is the rectifier and hopefully thats all. Most of the parts should be readily available and relatively inexpensive. We can piece this back together for you. I might have a spare used harness once I get my rebuild done but that won't be anytime soon. I think I still have my "5 minute harness" around here somewhere. I know the main green ground melted quite a ways up.

Take a multimeter. Ask him to remove the tank and check the main harness visually. The rectifier can be checked in less than 10 minutes. However if he sees you check things and there's not much wrong you might not get as good of a deal. What is the bike's general condition and how much DID he want?   

[TwoTired]

I forgot to add that any wires in contact with the ones carrying the heat load within the bundle can also get fried/need replacement.

I had that happen to a bike I bought off a wrecker.  It took a full day and wires from a spare harness to repair the bike.  But, it's fine now.

Cheers,

[750goes]

Jerry, TT,

Yes there were other wires touching and they showed evidence of being a bit stressed -so it will be a good exercise for my soldering & heatshrink skills if I manage to get this at a good price.

He did want $2500 as his reserve (remember this is Aussie prices), but it only got to $1625.00 (had about 30 bids from 5-6 buyers)..so I would think around $1600 was a fair indicator of its worth.

Bike presents very original except for new paint on tank & sidecovers, tank is good, covers 95%, no major leaks seen, but never been cleaned up either, brakes need flushing, obviously some electrics need sorting, good headers, seat been recovered but a good job, wheels, discs and spokes in good condition, frame overall no rust apparent..

Will be working out a plan of attack for the current owner and try to offer him what I think is a reasonable price - not rip him off but also not rip myself off...

I'll give the finance minister some warning there may be an economic downturn in my savings account coming soon....IF I report back it means I am still alive and can use my fingers to type....but I could also be strapped to a chair typing with a pencil stuck in my wired up mouth too....lol