|
|
12
|
|
I have a '78 single over head cam K model. The problem is that the battery (new) will not stay charged. The turn signals stop working when the battery gets low. When the battery is charged the engine starts instantly and runs strong.
Short in turn signal switches? Any suggestion on where to start.
Thanks!
Remember, you meet the nicest people on a HONDA.
|
|
|
I had the same problem, all of a sudden!
I kept trying to fix the cheaper stuff and that wasn't it.
It ended up being the rotor.
Try the rotor, the regulator/rectifier, and the stator first.
|
|
|
Do you have any test equipment (multi-meter) ?
Do you have a shop manual ?
It's pretty costly to just start replacing things one at a time.
|
|
|
Yes, I have a shop manuel. I will be checking the rotor, the rectifier, regulator and stator this weekend.
NOt something I really want to start getting into. I was looking for some simple things that might be the problem that someone else had discovered.
Thanks for the message. josh gates
|
|
|
I had the exact same problem with my '77. It turned out to be two problems. First, some of the wiring had started to corrode and wasn't letting the juice get back to the battery. After fixing that it would still not hold a good charge. After some poking around we found out that the fuse box had some issues. It was creating enough heat to melt plastic around some of the contacts. After replacing the fuse box and some of the wiring around it, the bike will charge back up. My turn signals still don't like to fire at idle but that's a battle for another day, just happy the bike is starting.
Also, i came across this the other day which made some sense after my fuse box issues. It's from a recall they did in the 80's.
1978 Honda CB750 Recall
Item Affected: ELECTRICAL SYSTEM:FUSES AND CIRCUIT BREAKERS
Date Announced: 1/14/1980
Description of Recall:
THE FUSE HOLDER CONTACT SPRING ON THE INVOLVED VEHICLES IS DEFECTIVE IN THAT IT CAN CAUSE HIGH TEMPERATURES TO DEVELOP AT THE FUSE, AND THE FUSE MAY FAIL. FAILURE OF THE MAIN FUSE WOULD CAUSE ALL ELECTRICAL FUNCTIONS TO CEASE, INCLUDING LIGHTS AND IGNITION.
Action Needed To Fix It:
DEALER WILL INSTALL A FUSE BOX WHICH CONTAINS A MORE EFFECTIVE SPRING, AT NO COST TO OWNER.
Good luck.
|
|
|
Thanks for the information. I just replaced the fuse box, I'm starting this weekend on checking the rotor, rectifier, stator, and regulator.
When the battery is charged it started on the push of the started button, when it gets low voltage it is hard starting.
Guess I have to just start checking the wiring. If I could find a new harness I would just replace it all.
Josh Gates.
|
|
|
You did the fuse box thing..next fire up the bike and disconnect the battery..does it keep running...if it quits it is the charging system..the bike will quit if you give it the gas also..as that is when a GOOD battery kicks in to keep it running and to assist the charging system when running...hook up the battery...put a 20 volt meter across the battery poles...should register 14.2 volts if everything is good...and less than 12 volts if it is not charging...but you MUST have 14.2 volts to have a good running bike..and if you are less than 14.2 volts the regulator CAN be adjusted with a phillps screwdriver..a No.8 wrench and a running bike to watch your meter reading across the battery terminals..
|
|
|
Thanks, this is the best reply I have received. Most just say read the manual. Josh Gates
|
|
Administrator
|
I hate to do this but 2tires is wrong. he gave you poor advice.
the sohc 750 will NOT stay running if the battery is disconnected when the bike is at idle. It WILL die. The sohc does not put out enough power at idle to keep the bike running. this will also screw up your readings if you take them at idle. You MUST have the bike over 2000 rpm to do this correctly. Over that rpm, you CAN disconnect the battery and you CAN rev the engine, it just cant drop below 2K.
Now your voltage reading does NOT have to be 14.2. It can be from 13.5 - 14.5 and be ok. the higher the voltage, the faster the battery will charge back up after starting or idling.
the other guys were right, you WILL have to do the manual and use a multimeter to test things. It is the proper way to do it. be sure to pay special attention to the connectors as said before. They get very corroded and can cause issues even if they look good on the outside.
Sorry 2tires but your info is not right.
The ride IS the adventure. The destination is just to get gas!
|
|
|
THanks, not looking forward to start taking the rotor apart. I'll try your suggestion. I appreciate your help. josh gates
|
|
|
Hello-
My bike is doing the same thing. (1980 CB750F SS) We tested it at idle and found 11.7V and at 2500K and got 12.3 V.
I was told the stator is bad. This seems to be a problem with these bikes they say.
Anyone know why they go bad?
My bike had 18K miles on it when the original stator failed. It was replaced with a used one and now needs
replacing again.
When we pulled the original out we bench tested it along with the new (used) one and all readings seemed
the same, but the original would not put-out voltage.
Regards
1980 CB750F Super Sport
|
|
|
Thank you, I will check it out first before I take the rotor out. My stator makes a Humming sound when the battery is low, does that sound like what your bike was doing. josh gates
|
|
|
On the stator, unplug the connector from the regulator harness then measure between all 3 yellow wires on the stator side of the plug. Honda says the reading should be .41 to .51 but in reality they measure all the way up to .80 to .90. Some of the extra resistance is the meter leads and internal resistance of the meter.
Now check each yellow lead to ground and it should be infinite resistance (open).
You don't have to take the rotor off to test it. Remove the left cover then measure across the slip rings with a GOOD QUALITY ohm meter. It is normally 4-6 ohms. Anything less than 4 is shorted and it must be replaced. Also measure from the slip rings to anything metal on the engine. It should be open, infinite reading. Any reading here is a short to ground. Also check the brushed. There is a line scored in each one of them. This is the wear limit.
If these things check out ok then let me know and we'll test the regulator.
|
|
|
THanks for the reply, I will start here this weekend. Any good places to get part you know of. Again, thank you for taking the time to reply.
Josh Gates, DC
|
|
|
Dr Josh wrote
Any good places to get part you know of. Again, thank you for taking the time to reply.
Josh Gates, DC
On the Rotor it's best if you can get one locally. A rebuilt one is about $150 but if you get it online you will have to not only pay shipping for the part but you will have to pay return shipping for the core.
|
|
|
It's usually the rotor on these DOHC bikes. The Sohc bikes are a whole different story.
Most of my good original rotors measure 4.5 ohms ±.2 ohms... either that or they are bad. I use a very high quality Fluke meter that is calibrated to include the resistance of the leads to check them. Rewound rotors will often measure higher, which is OK to about 5.2 ohms in my experience. Anything lower than 3.9 ohms is bad, and might burn out your regulator/rectifier if left too long.
What happens is the coil wire in the rotor has a coating on it. Over the years of vibration and heat, that coating gets worn down from winding to winding, and the windings start shorting together. Once numerous windings have shorted, the resistance goes down, and the magnetic field becomes less. Eventually there is not enough field to produce adequate power out of the stator, and the bike no longer will keep the battery charged. Also, the regulator tries to put more power into the shorting rotor, and sometimes it can burn out too.
The key is usually the resistance of the rotor. But, there is also a problem here, because the resistance can measure OK when stopped, but when spinning, the rotor is shorting out windings due to centrifugal force. Eventually, the rotor will become so damaged that it will measure bad when stopped, but it might take out the R/R by then.
|
|
|
Great explanation,genesound, I copyed and saved it for reference.
Thanks,
Karl
|
|
|
I would start by charging the batt. then unhook the neg. terminal and put a volt meter between it and the frame and see what it is drawing should be around .480 Milla amps unless something is pulling power constant
|
|
|
Thank you for the suggestion. I will give it a try. I haven't started to track down the problem yet, too much to do at home after work. I'll try to start on it this weekend. josh gates
|
|
|
Did you every resolve this problem? I have the same problem with my 80 K
|
12
|
Locked
