• Enter the March CB750 Supply gift certificate giveaway! It's easy... Click here, post something, and you're entered into the drawing!

Charging system, stupid question

motogtp

CB750 Addict
Messages
294
Reaction score
0
Points
16
Location
Des Moines
Stock '78 Super Sport w/ 6,000 miles, CycleX ignition, and new regulator/rectifier. My charging system seems to be all over the map. I have about 12.8V at idle but at 4000 rpm I am seeing over 16v. When I shut it off the battery reads 14.40V and it would drop 0.01V every two seconds. It eventually settled at 13.1V. Checking the terminal connection under the fuse box I get 1.2 ohms across the stator wires and no reading on the field wires. I know they are supposed to be 0.2 and 7.2 respectively. Is the charging system toast or am I measuring wrong? But here's my dumb question. I popped off the alternator cover to inspect the components and engine oil ran out (about 6-12 oz). Is there supposed to be oil in there? I saw a post earlier about someone's stator being rusty so I couldn't figure how it would get rusty if it is getting an oil bath.

Before I finished this post I went out to do the screwdriver/wrench slap test. Nothing! Main fuse is good, 13.09V at the battery, and I took it for a short ride this morning.
 
Last edited:
16 volts is too high...14.5 is best 15 is still OK. What regulator did you buy? If your specs are not right then start looking for another field coil and stator...they are all over ebay.

Yes there is oil under the cover on the sohc motor, it needs oil for the starter gear.
 
I,m almost positive there should be a small amount of oil in there to lube the starter clutch rollers and bearing I could be wrong, Sounds like the regulator is constantly exciting the field giving You the overcharge. To get a correct ohm reading wires should be disconected from any connection and tested directly to the component. Good luck.
 
Sorry Digger, We must have replyed at the same time, By the way did You get Your big bore together? As I recall You were waiting for the cyl. head.
 
Good advice guys. I got the rectifier/regulator from CycleX. I wired it up per instructions on this forum, the CycleX instructions weren't very clear. DD, you know the issues I have been having with this bike. The pilot screws now set at 1/2 turn out. With new plugs it starts and revs well but they are starting to get fouled after 5 minutes of idling. Even tried a hotter set today. Same result. I think I am chasing two or three issues that interact. Starting with the charging system tests next (it did pass the wrench slap test) and then a good carb rebuild and sync.
 
Is it a newer style electronic regulator? Not the oem style? Not sure what to say anymore about the plug fouling, Could probably figure it out if it was at my shop and sitting in front of me...kind of hard to diagnose stuff by remote:doh:

No dan not together yet. Waiting on APE to get me some special wrist pins. I got the cylinder head back but while waiting for the pins I have decided to replace the guides and cut the seats(should have had APE do it while they had the head but I was planning on having it together by now) I am having issues with the guide fitment in the head now so I have special parts and tools on order.:cussing:
 
Is it a newer style electronic regulator? Not the oem style? Not sure what to say anymore about the plug fouling, Could probably figure it out if it was at my shop and sitting in front of me...kind of hard to diagnose stuff by remote:doh:

No dan not together yet. Waiting on APE to get me some special wrist pins. I got the cylinder head back but while waiting for the pins I have decided to replace the guides and cut the seats(should have had APE do it while they had the head but I was planning on having it together by now) I am having issues with the guide fitment in the head now so I have special parts and tools on order.:cussing:

Yup, new electronic regulator. Yeah, remote diagnostics is tough. I am inquiring now for some local help. I get the feeling that I am missing something simple and hope that having another set of eyes on it will point that out. Thanks for all the help.
 
No Such Thing Lad. I had a really weird problem once. The engine on my 1970 CB-750 would shut down. I checked everything.
But could find nothing. one time I was checking the fuse and saw what looked like a small blob of solder inside the fuse. It turned out that the fuse holder had some corrosion where the fuse sat causing the fuse to heat up and melt the solder at the end of the fuse strip . The fuse looked fine. But when it warmed up it would disconnect. Maybe.
But the other charging problem I had was a bad stator that would quit when it warmed up.
Good luck
 
Back
Top