Topic: CB750 Not Starting/Stalling

[Christopharx]

Hello! So I'm very new to the bike world (today new) and I just picked up a 1982 CB750 custom from someone a couple hours away. Test drove fine, ran good, bought it put it in the back of a truck and brought it to where I live.. and that's where the fun ended.

Trying to start the bike, the engine turned over about three times, then nothing. Next time all I hear is a clicked. Wait about ten minutes and it turns over once, and on the next attempt to start it just clicking. This goes on for about an hour and someone who knows more about bikes than me comes over and shows me how to "pop start" the bike, it works! He ran the bike around the parking lot for  a couple minutes then let it idle, and as it was idling the lights got dim (unless revving the engine), and eventually the bike died. Back to the beginning, go to crank the bike and it's just a clicking.

The previous owner said it was a bran new battery and it started first try for him several times. Where do I start?

[crumpet8]

Doesnt sound like a big issue, but annoying none the less. Could be a few things but the first thing I would do is check the battery is actually new and charged (get a charger). Talk to the seller again, if hes nice enough. So many dodgy sellers out there.

The lights will always get dim after idling for a while, but with a fresh battery it should take waay longer than 2 mins, so it sounds like the battery isnt charged or being recharged.

In regards to the clicking, again Id start with the battery as you said previously the engine cranks over.

After you check your battery is good, try fire it up and if it cranks strong and starts up then all is good. Before going on any rides though, Id then start checking the charging system.

hope this helps Hopefully some more experienced people will also chime in too.

[calj737]

Battery is at fault. Either it's weak or your charging system is not functioning properly. Possibly bad ground connections will make the charging system not work fully and recharge the battery.

Definitely check the battery connections, and the NEG connection to the chassis. Probably loose or corroded.

[Christopharx]

I'll head to Walmart and pick up a charger and a multimeter, off the tops of your head do you know where I would find the grounds? I looked earlier and couldn't find anything.

[calj737]

Follow the cable from the battery NEG post to where it connects to the frame. Make sure that bolt is tight, and the connection at the battery itself is too. Any "wiggle" is a problem.

[Stev-o]

You have one or two problems.  Once the battery is fully charged [and dont buy an automotive charger!], wait an hour and check the voltage, should be around 13V.

Then, with the bike running, check the voltage at diff RPM readings: 2K, 3K, 4K, the voltage should go up if your charging system is working.

And dont ever believe a seller!

[CBGhia]

Yeah, it sounds like a bad battery.  I think if the charging system was really toast, then it wouldn't run with the battery being that dead. 

I bet the owner stuck it on a charger and it holds a charge long enough to get it to start once or twice and that is all.  Just enough to get it sold.

Get a good battery for it.  I recently with a Battery Tender brand lithium for my KLR and I'm quite happy with it.

[Stev-o]

  I recently with a Battery Tender brand lithium for my KLR and I'm quite happy with it.

Hey Joe....whats the latest with your 550/650? Last I heard you needed an exhaust...

[CBGhia]

  I recently with a Battery Tender brand lithium for my KLR and I'm quite happy with it.

Hey Joe....whats the latest with your 550/650? Last I heard you needed an exhaust...

I have a rigged up exhaust and I still need to wire it up.  I was hoping to hear back from Pamco Pete about a 650 version of his unit, because I donf't want to mess with the stock unit, but it does not look like that will happen.  I just need to start messing with it.

If you come across a good 650 4 into 1 or a good set of 4 into 4 headers, let me know.  You are always on the old craigslist.

[Christopharx]

Quick update, I had advanced auto parts charge it, put a multimeter on it. It dropped from 13.2 volts to 12.95 in about four minutes and still dropping.

[Christopharx]

It was the battery, the one that came with it dropped from 13.2 volts to 12.7 volts in about ten minutes and kept dropping, picked up a new battery and started right away and held charge idling for about ten minutes.I used the multimeter and kept checking the volts on the new battery, held at 12.35ish while idling and went up when RPMs did.  Starts up on first crank now. You guys are AWESOME! Thank you!

[Stev-o]

  I recently with a Battery Tender brand lithium for my KLR and I'm quite happy with it.

Hey Joe....whats the latest with your 550/650? Last I heard you needed an exhaust...

I have a rigged up exhaust and I still need to wire it up.  I was hoping to hear back from Pamco Pete about a 650 version of his unit, because I donf't want to mess with the stock unit, but it does not look like that will happen.  I just need to start messing with it.

If you come across a good 650 4 into 1 or a good set of 4 into 4 headers, let me know.  You are always on the old craigslist.

Will do.  Are you ever around Greenjeans home?  I'm buying a set of 750 pipes from him and need to pick them up at some point.

[CBGhia]

  I recently with a Battery Tender brand lithium for my KLR and I'm quite happy with it.

Hey Joe....whats the latest with your 550/650? Last I heard you needed an exhaust...

I have a rigged up exhaust and I still need to wire it up.  I was hoping to hear back from Pamco Pete about a 650 version of his unit, because I donf't want to mess with the stock unit, but it does not look like that will happen.  I just need to start messing with it.

If you come across a good 650 4 into 1 or a good set of 4 into 4 headers, let me know.  You are always on the old craigslist.

Will do.  Are you ever around Greenjeans home?  I'm buying a set of 750 pipes from him and need to pick them up at some point.

He lives 30 minutes north of me.  Are you driving up here? We should chat via PM

[Christopharx]

Hey, sorry to bump this thread but I'll post another update for you. This might be a coincidence, or it might be the same problem I was having.

After riding the bike for a couple of days, one time it just didn't start up.. No noise no clicking no nothing again. After hours of frustration I talked to my dad who in a matter of two minutes walked me through jumping the solenoid and it started right up. Then cut it off, and tried pressing the button while banging the solenoid with the bottom of a screwdriver, again started up. Now it starts every time, I'm gonna get a new solenoid anyway. Anyone googling away for a possible solution to your problem try jumping your solenoid by quickly taping both terminals with a screwdriver on your solenoid. You can unplug the the wires (not the terminal leads) going into it if you want, it'll attempt to start either way. If it does start by jumping it, try banging it and see if it works; if not your problem is probably before the solenoid. If neither jumping it, nor banging worked it could be the battery, or a problem down the line (towards your starter).


Again thanks for your insight and help guys, just throwing this out there if anyone else has issues similar to mine and would like to save the several frustrated days.

[crumpet8]

If you haven't ordered a New relay already you should try cleaning the one you have. Over time, the parts corrode and stick so the connection doesn't work as it should. I saved a few quid doing this some require soldering however... not sure about this one, but worth a shot,