TOPIC:

i recently purchased a 1978 kz650. the stator was only putting out 35 VAC at 4k rpm so i bought a used one of ebay. the new stator is putting out 75 VAC at 4k rpm which from what ive researched on here is correct. now i am still having charging issues. when i rev the gas and check the voltage on the battery its only reading 11.78. i can leave the bike off all nite and it will still read 11.78 so i dont think its a bad ground. my next guess what the regulator/rectifier but im not sure how to test this. can someone please help me with testing the regulator or any other suggestions of what to test or what could be wrong? thanks!!

A suggestion is to first fully charge the battery,clean all battery terminal connections and the ground where it goes to the frame/engine.

Clean all electrical connectors(the bullet type and the block connectors) of the green crud of corrosion and spray them with a good electrical contact cleaner(not WD-40)before reconnecting them.

The battery plays an important role in the operation of the electrical system and should be checked with a hydrometer for spcific cell gravity after it is charged. A hydrometer can be purchased at any good auto part store and is nothing more than a glass tube with some floating balls that is used to get a sample of battery fluid.

bobbisman wrote:

i recently purchased a 1978 kz650. the stator was only putting out 35 VAC at 4k rpm so i bought a used one of ebay. the new stator is putting out 75 VAC at 4k rpm which from what ive researched on here is correct. now i am still having charging issues. when i rev the gas and check the voltage on the battery its only reading 11.78. i can leave the bike off all nite and it will still read 11.78 so i dont think its a bad ground. my next guess what the regulator/rectifier but im not sure how to test this. can someone please help me with testing the regulator or any other suggestions of what to test or what could be wrong? thanks!!

Hello, bobbisman, and Welcome to the forum! We're glad you're here!

Seem to recall a complete 1978 KZ650 repair manual being somewhere here on the KZR site, or via a link or reference from here to another site. Or might conduct an on-site search for diagnosing the particular part involved. Am expecting someone will be along soon with better more specific directions.

Meanwhile, if not already done, and as suggested by MFolks, would go ahead and assure a good solid ground connection where the negative battery terminal attaches to the engine or frame. Most of the bike's electrical components do rely on grounding to the frame for return to the negative battery terminal. At least that's my understanding. Would also double-check all the wiring connectors for a good clean snug fit, and for any blown or loose fuses.

And of course assure clean tight connections at both battery terminals.

[click here for link to] > KZ650 Wiring Diagrams

Also may check "Filebase" under "KZ Information" in above green header ribbon, and navigate to the particular year and model.

11.78 volts doesn't qualify as a fully charged battery, so would be better to get it fully charged before relying on the following quickie test (but everybody knows you'll likely try it anyhow ).

Could try this test (with good fully charged battery, good battery ground connection , and assured good solid wiring conections everywhere else) ---
With ignition off, unplug green regulator connector from electrical panel. Start engine. Run at 5000 rpm with headlight lit. If meter across battery terminals now reads more than 15 volts, regulator is defective. If less than 15 volts, either dynamo or rectifier is defective.

Z1 Enterprises lists this combination unit (temporarily out of stock):
[click here for] > Z1E's reg/rec combo

Please Note -- This test presupposes that the green connector is for the regulator on the KZ650 as it is on the Z1/KZ900/KZ1000.

Good Luck!

so i made sure the battery was fully charged for this morning. just incase i put a boosterpack in my backpack along with a voltmeter. i drove the bike all the way to work on the highway which is like a 10 minute ride and when i got to work and checked the battery with the bike still running it barely reading over 9 volts. i would think being in 5th gear and running between 6-7k rpm would charge the battery. i tried finding the green plug your talking about but couldnt locate it. would it be a different color plug where my regulator/rectifier are one unit?

Every charging problem I ever had was because of bad batteries. I got 2 bad ones in a row. The only way I could tell was to check each cell with a hydrometer.

bobbisman wrote:

so i made sure the battery was fully charged for this morning. just incase i put a boosterpack in my backpack along with a voltmeter. i drove the bike all the way to work on the highway which is like a 10 minute ride and when i got to work and checked the battery with the bike still running it barely reading over 9 volts. i would think being in 5th gear and running between 6-7k rpm would charge the battery. i tried finding the green plug your talking about but couldnt locate it. would it be a different color plug where my regulator/rectifier are one unit?

Am thinking the mentioned regulator test is possible only where the rectifier and regulator are separate units whereby the rectifier remains functional during the test. So the combo reg/rec unit may not permit such test.

At idle rpm, voltage across battery terminals should be about 13 volts. At 3000-4000 rpm, voltage across battery terminals should be be 14-15 volts.

Good Luck!

if i completey charge the battery and then start the bike and let it idle the voltage will be around 11.8. if i drive it around for a while and check the voltage it will be even lower and if i keep driving eventually the bike will just die from the battery being so low. so its like the battery is not being charged when the bike is running. i have now replace the regulator/rectifier but still no luck. if i let the bike sit over nite and test the battery after all this has occured the battery will gain voltage back but as soon as i try to start it again the voltage will drop to between 9 and 10 volts depending on how low the battery was drained. i am absolutely stumped:unsure:

How old is your battery? I'm having the same issue, replaced the stator and upgraded to the
rectfier/regulator combo fron Z1E, same issue.
Used a hydrometer and found (2)cells to not
fully charging might need to replaced the battery.

its brand new

How long did you charge the battery?
After you charged the battery what was the voltage? It should be as high 13 volts, then settle down in the mid to high 12v (12.6-12.8).
But you might want to try a hydrometer to check each cell.

Check and clean all connections and make sure the system is fully grounded.

Are you having any issues with other electrical units (lights, turn signals, and taillights)?

If you go to the KZ information tab, under filebase you'll find a wiring diagram for your bike, if you don't have one.
There different models for the 650's, so you might want to include this info.

Hi gang, I seem to have the exact problem on my 78 kz650. I have gone thru 5 different stators 3 differnt regulators and changed the flywheel 3 times. on my 2nd battery now. the batery charges fine checjked with a hydrometer. voltage in the morning is @ 15.4 after charging. after 3 days of riding the voltage with the key off is 12.1 with the key on drops to 11.55. pulling my hair out on this as there arn't many parts to work with.

spudbudy wrote:

Hi gang, I seem to have the exact problem on my 78 kz650. I have gone thru 5 different stators 3 differnt regulators and changed the flywheel 3 times. on my 2nd battery now. the batery charges fine checjked with a hydrometer. voltage in the morning is @ 15.4 after charging. after 3 days of riding the voltage with the key off is 12.1 with the key on drops to 11.55. pulling my hair out on this as there arn't many parts to work with.

Check and/or clean all connectors.
Confirm a good ground source.