Topic: 1979 CB650 Electrical issue

[Jonnynewbreed]

Starting a new project and I think I effed up.

Put the old battery on to test electrical and got lights to turn on, starter just clicked due to lack of power, but good sign.

Charged up new battery and put it on and while I was connecting the negative I had a big spark and the 30 amp fuse blew. Turns out my kid turned the ignition to on (he's two, so totally my fault for not double checking). I've replaced the fuse, but am now getting nothing. The ignition switch is not great so I jumped the ignition to test it out and still nothing.

I'm going to check the rectifier/regulator and other electrical to see what is dead, but I thought I'd post as I've been lurking for a while and have read lots on charging issues and even a post on blowing the 30 amp fuse also fries the rectifier.

Fortunately I found a full harness with replacement parts on kijiji for $100 (used), which should give me the replacement parts I need.

Any advice on troubleshooting...other than me not being an idiot in the future?

[calj737]

Confirm your battery polarity. Sounds more like you have reversed the leads.

[Jonnynewbreed]

I feel pretty dumb. I definitely tried to hook the battery up backwards, which is what caused the Spark and fuse blow out. I've since put it on the right way, but still getting nothing. Just checked and power is going into my main fuse, but I may have blown something up beyond that.

Yes I am an idiot. No, I wasn't dropped on my head as a child, which is to say I can blame no one but myself.

All that aside, what is my next move? I'm trying to figure out how to pinpoint the fried component so I can mount it on a plaque and hand it beside my shaving mirror.

[calj737]

Is power coming out of your main fuse? Check both sides with a meter.

Check the key switch for 12v in the Black wire.
Check for 12v at the coils with key in ON position.
Check the RUN/STOP switch too.

Your bike may require the clutch be pulled in to start; I'm not terribly familiar with 650s. Confirm all these little bits and report back.

And do measure the voltage at the battery please.

[Jonnynewbreed]

I'm getting power out of the man fuse from the plug in the top, but nothing out of the black wire going into the engine block. Getting power from my key switch from the red wire, but not the black wire. Fuses are all intact.

Battery voltage is 12.5

All I'm trying to do at this point is to get the lights to turn on. I'll check the engine by opening up the crank case before I hit the start button as I picked the bike up and want to make sure nothing is seized before I try to start it up.

As I mentioned, I was able to get the lights to turn on with my old weak battery, but as soon as I (incorrectly) hooked up the new battery and blew the main fuse I get no lights turning on.

I really appreciate the advice here guys.

[Airborne 82nd]

Isn't black switched power from the key sw.? check the sw. Also if you hooked up the battery back asswards you more than likely have fried the rectifier.

[Jonnynewbreed]

Fixed!!!

Pal came over and really knows how to check electrical. Turns out the main fuse I replaced was dirty and needed to be cleaned to make contact. Bike lights up and engine turns over.

Carbs go in next, gas tank put on and spark plugs replaced this week. From there I'll fire her up.

[calj737]

Reply 3 

Too often with fuses, if you blow them, simply replacing them will not yield good results. Gotta do a proper job cleaning the holder.

Glad it worked out for you! These bikes work so much better with good pals around 

[Jonnynewbreed]

Very true. Thank you for the advice. Such a great group here.