Topic: Fried Rectifier

[MIKE029]

What Have I Done
 '75 CB550 w/33K on odo. Picked up a few weeks ago. I've got her up on my lift and still going thru "discovery". Starts & sounds good, no leaks, seeps, or weeps. But after a test run the other night I notice a cooked harness on the rectifier assy. What gives? I was using a battery out of a quad to jump start it, 12V14A. The stock item is a 12V12A ( just arrived from bike bandit), but I didn't think that would be a problem. I also have all the rear turn signal & tail light removed.   Any help would be appreciated . . . . thanks  MIKE029 

[Queeg]

did you cook the wires or did the p/o do it?

  numb er 1 cause is hooking the battery up backwards or jumping the bike with the cable on the wrong terminals.. i have done it. when it was dark out.

 i just went to the electronics store got a new one and it worked better than the stock one.
  added a diffrent voltage regulator and it has not gone dead in 6 months and im using a battery i had for like 6 years
 if you want a new stock on . honda told me last summer there was 6 left in the u.s. and they were 265$

  there are many options to fix it.. just solder new wires on it is an option but, if the rectifier is damaged in the slightest it will cause charging issues!

[GammaFlat]

Jumping with another vehicle is bad when the other vehicle is running... can "rec" your rectifier.  Always leave the jumping vehicle off and of course backward jumping is bad. 

There are threads here on how to test them - here's one: http://forums.sohc4.net/index.php?topic=2229.msg16207#msg16207.  If you find that it's bad, you have options... You can try to find a used one, new one or build one.  Building one is not as big a deal as it sounds.  The total in parts is probably 10 or 15 bucks using good components (2 rectifiers, connectors, wire, heat sink). 

If you want to build your own, we can get through this  

[TwoTired]

I don't believe it matters during a jump if the donor vehicle is running or not.  There are nothing but old wives tales to support this claim and no technical foundation.

Reversing polarity will usually, bag the rectifier, and overload green and red wires between the rectifier and the battery.  There is no fusing in this circuit.
If the rectifier shorts instead of opens during the failure, then any power connection will melt wire insulation.

Check/measure the six rectifier diodes, and replace as necessary.  Also, replace any wires found with damaged insulation.

[MIKE029]

Thanks . . .
 Checked diodes & they tested good. Stripped insulation off the only 2 wires that were cooked & re-sheathed. Yellow diode wires were OK.  I guess I'll plug it back in & fire it up again. Obviously the charging system is putting out good juice.
 Cause ?  Not certain but I would have to say probably a backwards jump. Eager to show it off the other night & in the heat of the moment I seem to remember cranking it a bit before re - setting the mini jump cables I made.

        here's a question . . .  when battery is hooked up wrong is the starter & engine turning backwards ?? had an old Bultaco that would start ( and run ) backwards.

[steam-powered man]

pm sent re: inexpensive spare i have.

[Queeg]

Thanks . . .
.

        here's a question . . .  when battery is hooked up wrong is the starter & engine turning backwards ?? had an old Bultaco that would start ( and run ) backwards.

  also another way to cook the rectifier and wiring

ive done that too

[TwoTired]

        here's a question . . .  when battery is hooked up wrong is the starter & engine turning backwards ?? had an old Bultaco that would start ( and run ) backwards.

Yes, the starter motor can turn backwards.  But, the one way roller clutch will not engage, so it won't spin the motor at all.  Even if it did, a 4 stroke motor will only run in one direction. The SOHC4 has a 4 stroke motor.

However, reversing the battery terminals will make the rectifier turn on and place a dead short across the battery connections.  If the battery has enough power to turn the starter, it will turn the wire insulation between battery and rectifier to smoke in about 0.5 seconds.  This smoke is toxic and unless you are wearing breathing apparatus, you will lose any focus on the starter button long before any worries about turning the motor over with the starter.

I think that covers it.