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I have a 1980 cb750c, I had all the electrical working perfect the other night, but the battery was a bit drained from getting the carbs set to where the motor ran perfect. I put the battery on charge over night but failed to realize that I had the ignition switch on the park position instead of off. Anyways came out to start it today and no lights came on, on the bike and the electric start button didn't work. I used a screw driver to jump the starting solinoid and it started perfect with the key switched to on but didn't start with the key switched to off like it is supposed to but no lights or electric start still. I don't know if it is the ignition switch that is broken or it maybe a relay? All fuses are good. Has anyone ever ran into this issue, or can anyone think of what could be wrong?? Thanks
 

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First of all, I am no expert on that particular bike. But having worked on Honda bikes of similar years, I am wondering if your main fuse let go. the main fuse is a thin strip of exposed metal that lives right under two screws on the solenoid.
They are called dogbone fuses because of the resemblance to a dogbone

Like this https://images.search.yahoo.com/images/view;_ylt=AwrB8o_yxzFVMTAAfBMunIlQ;_ylu=X3oDMTIyOG0xbzA2BHNlYwNzcgRzbGsDaW1nBG9pZAM5ODJiZDNjNDhiYjEyNWE2MTBmZDM4YWQ5OTk2NmU0NwRncG9zAzIEaXQDYmluZw--?.origin=&back=https://images.search.yahoo.com/yhs/search?_adv_prop=image&va=honda+dogbone+fuse+motorcycle&fr=yhs-mozilla-002&hsimp=yhs-002&hspart=mozilla&tab=organic&ri=2&w=225&h=169&imgurl=thumbs3.ebaystatic.com/d/l225/m/mumZiOzvzgXKZh9qlUDmS3Q.jpg&rurl=http://www.ebay.com/sch/i.html?_kw=honda+amp+fuse&size=+5.9KB&name=PACK+OF+30+AMP+NEW+OLD+STYLE+<b>HONDA</b>+<b>MOTORCYCLE</b>+FLAT+BLADE+<b>FUSES</b>&p=honda+dogbone+fuse+motorcycle&oid=982bd3c48bb125a610fd38ad99966e47&fr2=&fr=yhs-mozilla-002&tt=PACK+OF+30+AMP+NEW+OLD+STYLE+<b>HONDA</b>+<b>MOTORCYCLE</b>+FLAT+BLADE+<b>FUSES</b>&b=0&ni=160&no=2&ts=&tab=organic&sigr=11hgotghk&sigb=14si3bkdo&sigi=11r2tgtf9&sigt=12jp158t5&sign=12jp158t5&.crumb=lG7ysNBXj0m&fr=yhs-mozilla-002&hsimp=yhs-002&hspart=mozilla.

I have seen these fuses simply corrode into dust, and I have replaced mine with an ATC fuse holder and fuse on a couple of bikes. https://images.search.yahoo.com/images/view;_ylt=AwrB8o_yxzFVMTAAfBMunIlQ;_ylu=X3oDMTIyOG0xbzA2BHNlYwNzcgRzbGsDaW1nBG9pZAM5ODJiZDNjNDhiYjEyNWE2MTBmZDM4YWQ5OTk2NmU0NwRncG9zAzIEaXQDYmluZw--?.origin=&back=https://images.search.yahoo.com/yhs/search?_adv_prop=image&va=honda+dogbone+fuse+motorcycle&fr=yhs-mozilla-002&hsimp=yhs-002&hspart=mozilla&tab=organic&ri=2&w=225&h=169&imgurl=thumbs3.ebaystatic.com/d/l225/m/mumZiOzvzgXKZh9qlUDmS3Q.jpg&rurl=http://www.ebay.com/sch/i.html?_kw=honda+amp+fuse&size=+5.9KB&name=PACK+OF+30+AMP+NEW+OLD+STYLE+<b>HONDA</b>+<b>MOTORCYCLE</b>+FLAT+BLADE+<b>FUSES</b>&p=honda+dogbone+fuse+motorcycle&oid=982bd3c48bb125a610fd38ad99966e47&fr2=&fr=yhs-mozilla-002&tt=PACK+OF+30+AMP+NEW+OLD+STYLE+<b>HONDA</b>+<b>MOTORCYCLE</b>+FLAT+BLADE+<b>FUSES</b>&b=0&ni=160&no=2&ts=&tab=organic&sigr=11hgotghk&sigb=14si3bkdo&sigi=11r2tgtf9&sigt=12jp158t5&sign=12jp158t5&.crumb=lG7ysNBXj0m&fr=yhs-mozilla-002&hsimp=yhs-002&hspart=mozilla Sorry-- just hit the back button on the dogbone image and you will see the ATC replacement fuseholder. It is not beautiful, but you get the idea of the fuseholder installed on the bike

Maybe someone who knows your bike model will happen along and can tell you for sure if your bike has such a fuse
 

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I have a 1980 cb750c, I had all the electrical working perfect the other night, but the battery was a bit drained from getting the carbs set to where the motor ran perfect. I put the battery on charge over night but failed to realize that I had the ignition switch on the park position instead of off. Anyways came out to start it today and no lights came on, on the bike and the electric start button didn't work. I used a screw driver to jump the starting solinoid and it started perfect with the key switched to on but didn't start with the key switched to off like it is supposed to but no lights or electric start still. I don't know if it is the ignition switch that is broken or it maybe a relay? All fuses are good. Has anyone ever ran into this issue, or can anyone think of what could be wrong?? Thanks
What you just said in the above post is not possible unless you're saying it wrong. Please repost an accurate description of the problem. Perhaps we can help...
 

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My description is bang on with what happened I have worked on bikes all my life and never run into this it's like the battery charging overnight burnt out the ignition switch. The fuse under the seat is still all good I took it out and replaced it just to be sure. There is a diode under the seat located close to the battery maybe it could be broken?
 

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I used a screw driver to jump the starting solenoid and it started perfect with the key switched to on but didn't start with the key switched to off like it is supposed to
Huh? Say What???

If you can jump the starter and make it spin then you've got a good battery and a good starter.

Starter SWITCH should not burn out.

Sounds like perhaps your starter SOLENID or starter RELAY fried.

Try jumping 12V to the START terminal on your solenoid and see if it cranks. If so, then your solenoid is good.

Then backprobe (stab, etc) the output from your starter switch and see if it's putting out 12V when you press it WITH IGNITION on.

After that check your kill switch, kickstand switch, neutral safety switch and starter relay or whatever it is that integrates those switches and gives the solenoid a go/nogo signal.
 

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TRy this

OK, first of all, I thought your bike was a Nighthawk or something. It turns out that my 1979 CB750K is almost a dead ringer for your bike,but a year older.

The starter solenoid on my bike has a dogbone fuse mounted right on it. If that fuse blows, the bike would still crank if you shorted across the solenoid, but no way would the key and start switch operate it. There is a little panel on the side of the solenoid, appearing as a flat spot with some kind of little latch. Easy to miss if you do not know it is there. Anyway,the dogbone is right behind the little panel and outside the seat,not underneath.

So please tell us what you find.
 

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I used a screw driver to jump the starting solinoid ... but didn't start with the key switched to off like it is supposed to
This doesn't happen. As two others have suggested.

If it could happen the bike would continue to run when you turned the key to the off position.
 

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He probably thinks the keyswitch is like a car, for all we know. 1st position,ign,second position to start. When you back it off from second position,it is "off".

Anyway,being rude to an EE and also a practicing pro motorcycle mechanic by informing of "years of experience"does not make a great deal of sense. I ignored the on-off switch thing, just figuring that we could get the bike going.

Now I do not care so much.............
 

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He probably thinks the keyswitch is like a car, for all we know. 1st position,ign,second position to start. When you back it off from second position,it is "off".

Anyway,being rude to an EE and also a practicing pro motorcycle mechanic by informing of "years of experience"does not make a great deal of sense. I ignored the on-off switch thing, just figuring that we could get the bike going.

Now I do not care so much.............
I'm one to get curious about things once the door is opened. However, I'm not sure what is meant by working on bikes all of your life. I'm not certain I would have known what end of a screwdriver to use when I was one week old.

I wonder what kind of charger he left it on over night.
I'm not certain what the switch is like on his bike, but I did have the one on my '78 CB750 do an interesting trick. Long story short - it got a little sloppy with age and that created a loose connection which led to some heat generation that melted part of the plastic. That made the spring loaded contact get gripped with the spring in compression such that it failed to make contact. The fault reared its ugly head for the first time while I was on a trip from the east coast to Lansing, Michigan. I could clean out the slot and get it to function again on the roadside. I found out slapping the shxt out of the switch gave temporary relief. That was while attempting to pass an 18 wheeler in heavy traffic. Not the time you want a dead motorcycle under you.
 

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so instead of pushing the start button, you jumped the solenoid with a screw driver?
did you try the start button?
My old 750 only did this once, i took a doublejack sledge hammer and threatened to beat it to death... never happened again.
 

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This doesn't happen. As two others have suggested.

If it could happen the bike would continue to run when you turned the key to the off position.

Gee... I didn't mean to sound ugly when I posted to the OP. But that's the statement he made that I had a problem with. If the key is off, and you jump the solenoid, the starter will spin, but the bike won't start. So why would the OP expect it to start and run when the key is off??? :confused:
 

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Gee... I didn't mean to sound ugly when I posted to the OP. But that's the statement he made that I had a problem with. If the key is off, and you jump the solenoid, the starter will spin, but the bike won't start. So why would the OP expect it to start and run when the key is off??? :confused:
Beats a weeks worth of crap out of me! I thought I'd landed in an alternate universe.
 

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No worries about the OP

At this point, what difference does it make??? If you read the original post, he says that all the fuses UNDER THE SEAT were all good. Look at this:

http://www.hondapowersportsoftroy.com/fiche_section_detail.asp?section=2569535&category=Motorcycles&make=Honda&year=1980&fveh=133012

See part 25? Those fuses are located in the center of the handlebar bridge. I can also confirm this personally because my own motorcycle has them...4 fuses all 10 amps with one spare. Also a dogbone fuse on the starter solenoid.

A guy who does not know any more about his own bike than this,especially when every time you look at the speedometer, right underneath,it says "Fuse". Pretty good odds that taking a screwdriver to remove the fuse panel would be a good first step to solve the problem....

So he comes here and instantly gets all butt hurt and tells us about all his experience, well he should just grab a tissue I guess. Anyway,guys, you are good people just trying to help out, but sadly you cannot save them all....

I get in these moods once in a while, so thanks for letting me vent. I guess that now I need a hug from Moni :p
 
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