so i have a 1993 CBR900RR.
I was riding it around and it felt like i was out of gas, but i just filled up. took it to a shop, turns out its not charging the battery.

They told me i need to replace the stator and the alternator rotor.

now my question is: what can be bad about the alternator rotor?

From what i see in the haynes manual, from pictures and what not, its just a piece of metal. is it magnetized or something that i cant tell by the picture?

I haven't taken it apart yet, but i have looked online and the alternator rotor isn't exactly cheap, and i hadn't planned on replacing it so its kind of out of my budget at this point.

Just kind of wondering why i would have to replace the rotor, and if there was a way i could "recharge" the magnet to save on money, if that is even possible.

any and all help will be greatly appreciated. thank you!

 

or is there a way to check if the alternator rotor is bad?

 

I have read that you can test the resistance on them so I would assume they can go bad, but I don't know much about diagnosing them. Very good question! I'm surprized no one has answered.

 

Most common issue when a battery isn't charging is a bad stator or a bad regulator rectifier. The 'alternator rotor' doesn't go bad. It is just a big piece of metal that spins inside the stator, producing electricity, just as you surmised. It seems like there might be a miscommunication or misunderstanding. I will say this - the part that is truly bad can be determined with proper testing so you wouldn't have to replace BOTH the stator and the reg/rectifier (R/R), as that will be expensive to do both. Maybe you need to retrieve your bike and go to another shop? Sometimes the real 'problem' is just the connector from the stator to the R/R melting down. I wonder if the shop even bothered checking that? Good luck my friend. I've been through R/R problems with a VFR and I've been through stator problems with a CBR929RR. Both are a nuisance, but I'd rather replace a R/R anyday! The stator is a PIA to get to and replace.

 

alright good deal! thanks for the info! yea i already got my bike back from that shop, i dont think they know what they are doing since they replaced so much other stuff, then said OH, its the stator. so needless to say i was a little upset to have my bike sitting there and spending money on parts i didnt need. on a plus side tho i pretty much have a new bike minus the charging system haha.

Looking through the haynes it seems its pretty easy to test the battery, r/r and stator to see which one is bad, if not all. so ill be doing that today or tomorrow and ill post back on here what i find.

thanks for the help!

 

alright, so i tried to get the bike started today, jumped it from my car, has guage lights and everything, no headlights though. thinking it may just be a fuse or bulbs to fix that issue.

The bike turns but doesnt fire up. so tomorrow i guess im going to tear her apart, check the plugs for spark, give them a clean, and then possibly take the carbs off and give them a proper cleaning.

Still havnt checked the stator and r/r yet, will most likely end up doing that while i have the fairings and tank off tomorrow.

 

Frog, I'm not saying your wrong. I searched a couple different searches on google. I don't remember the exact wording I used. One was similar to "how to test an alternator rotor" and one was "do alternator rotors go bad". There were some links that said they do go bad. There were YouTube videos of people replacing the rotor. Some mentioned the resistance can be out of spec. Some mentioned that they can demagnetize. I know a little about how the charging system works involving the battery, stator, and r/r. But I have never heard of them going bad. Maybe it's one of those rare occurrences?

 

I had the exact problem that you had (charging) on my 1993 CBR900RR. check the connection under the seat in front of the battery. See if they are melted. if so repair, I just soldered and heat shrink the wires and eliminate the connection. Check the rectifier regulator. Pull it from the harness and see if the plug or Rectifier / regulator is melted.



Here is a picture of the plug for the rectifier plug on my bike.



You can see that the rectifier/regulator is also melted.



The original is on the left. the new one on the right has cooling fins. If you change the rectifier/regulator put some CPU grease on the bottom then bolt it to the frame. The grease will help dissipate the heat better.

Disconnect the 3P connector under the seat use an ohm meter to check the stator wires and ground there should be no continuity between the stator wires and ground. Check between each of the stator wires resistance should be 0.1 - 0.3 ohms.

Replace the stator id the resistance is out of specifications or there is continuity between yellow wire terminal and ground.

 

thx for the tip. I will be doing this. gets so dang hot down here, every little bit helps.

 

alright so i tore the bike apart today. the r/r looks fine, but im having trouble testing it.

The connector from the stator behind the battery is melted. is there a way i can still test the stator to see if its just the connectors i need to repair?

thanks for all the help so far. im trying to figure out what all needs to be replaced so i can order all the parts at once instead of a part at a time and my bike being down for weeks instead of a week haha. My real concern is thinking i fixed it, going for a ride then getting stranded on the side of the road since i dont own a truck or a way to haul it back haha.