help please, anyone lol

[karcher]

I bought an 1976 honda cb750a, great bike. I have owened it for a few months now. it has a new battery. One day i was driving and i felt the battery dying, so at a red light my bike completly dies. I had a friend come give me a jump and i made it home and then the bike wont start back up unless jumped. The bike will also only stay on if its in gear and im reving it. Any insight on this problem would be appericated and helpful

[TOOLS1]

The battery problem sounds like it is not charging. You can download the factory service manual from the manual thread on the home page here. It has detailed instructions on testing the charging system. Also the charging system is the same as the "K" and "F: models. The running problem sounds like plugged pilot jets. They will need to be removed to properly clean them. However they are a pressed in jet and can be tricky to remove. There is a thread here somewhere on removing them. Search for "removing pressed in pilot jet," or removing pressed in pilot jet from keyhole carbs."
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[Re-run]

With the cb750, the engine has to be turning 2000+ rpm in order to charge the battery. When you get below that, it pulls from the battery and so if the battery is going dead, the bike will die. I had this happen once, but it was just a battery that I neglected to add water too and charge before riding the first time that year.

Very quick test is to charge the battery then start the bike. Hook probes to the battery and rev the engine. Your voltmeter should read at least 13.5 volts, but it shouldn't go over 14.5 really. If it starts to hit 14.8, the battery will start to cook its water off from over charging.

My guess is that the voltage won't climb to required levels. The rotor and stators on these bikes are pretty good, it is usually the regulator or rectifier that go, so I would start with testing those. The regulator is mechanical and can be adjusted, if it is out of spec. If you have to replace 1 of those, I would get the reg/rec combo unit.

[karcher]

Thank you both for the advice, my battery doesn't have water. i plan on testing it more today and try and find out whats going on with it

[LukeM]

This is presuming you have a lead/acid battery, and not one of the gelcell or AGM batteries:

Depending on how long you run it with little or no water, you may have killed it.  Charging a battery while low on electrolyte is very hard on the plates.

Use distilled water to fill it enough to cover the plates.  Try not to overfill.
Put it on a low current charger/tender overnight or longer.
Once it's done charging, check the voltage.  Ideally it will be at 13-13.5v with no load.

If the charging system is fully functional, you should see 14-14.5v at the battery terminals when the engine is at 2000 rpm.  Any higher than 15v, and you may have issues with the regulator.  Less than that, and your rectifier may have issues (bad diode, corroded yellow wire connection, stator/rotor problem).

Again, the FSM has good procedures to test the charging system.

I hope this helps.
Luke M

[karcher]

The battery doesnt require water, but a quick question. I installed a new battery after buying the bike and of course i drive fast(very fast). could that have over charged or fried anything?

[Re-run]

So, you put in an agm or gel battery, or maintenance free? If any of those, then adding water isn't needed.

As for driving fast, no that would not over charge anything unless there was some issue with the regulator.

[karcher]

i feel as if it is the reg or the rec. Does anyone know a guide to replace these? Im guessing its not the alternator because if i hold my throttle in the bike will stay running. But if i let it go then it dies and wont start up. i can get it to start by jumping it. i did jump it with a car the first time it died... and then the second and third time also. so im guessing i might have fried a few things. all my lights work still if that matters.

[Re-run]

You may also want to load test the battery. Not likely the issue but if a running voltage test comes out good, that would be the next check.

Also, when jumping, make sure the car isn't running. You can really do some damage to your electrics and battery if the car is running.

[karcher]

yeah i have been learning alot from this form. I will never do that again. and thanks for all your help guys. Ill be testing everything after finals and ill post an update

[Maz]

Karcher,

click this link for a very useful 'Motorcycle charging system trouble shooting guide'.
Works for any bike and I've used it many times.

https://www.electrosport.com/media/pdf/fault-finding-diagram.pdf


Maz

[karcher]

Sent from my iPhone

On Apr 30, 2015, at 1:55 AM, Maz [via Honda CB750'S] <[hidden email]> wrote:

Karcher,

click this link for a very useful 'Motorcycle charging system trouble shooting guide'.
Works for any bike and I've used it many times.

https://www.electrosport.com/media/pdf/fault-finding-diagram.pdf


Maz

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NAML

[shinyribs]

Plug wire? Sorry, I don't think the pic uploaded very well. Hard to make out.

[karcher]

it looks like its some kind of drain tube? but on other news, i went and tested my battery and it was done for. bought a new battery and put my kick start back on and the bike came back to life. but does anyone know where to put the kick start on at? its always in the way of my foot peg

[TOOLS1]

There is a place for the kickstarter right under the seat. It lays across the top of the battery box. There is a part with a nub that the bottom of the kickstarter slips over bolted on behind the gas tank bracket on the right side, and the top lays to the left at the rear.
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[karcher]

I hope everyone reading this is enjoying the weather today, glad my bike is back and running. Thanks to all that helped.

-Archer