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Charging Issue 1982 Honda CB900F Super Sport

CBRiderNYC

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Hi I’ve got a 1982 Honda CB900F Super Sport a that is having charging issues (I also plan to switch to an antigravity lithium ion battery but currently I am still using a New Lead Acid Battery in the Bike)

Currently at idle it only puts out 11.7-11.8Volts DC & @5000 just barley hits 13.1-13.5

The previous owner replaced the rotor and stator & I have put a new ricks lithium ion rated regulator rectifier on the bike. (it caps out voltage @ 14.5V so as not to damage the lithium battery)

The first step I took was to replace the brushes since they were a bit worn, and had some success, the bike is charging better. I can now get about 3 or 4 rides out of it before the lead acid battery dies on me. (But it’s still putting out not enough volts to support a lit ion battery which needs at least 13 to start charging)

I’ve test the rotor and measured 6.4 ohms across the slip rings. (This seem high and out of spec to me) I’ve also confirmed that it is not shorted to ground.

The stator appears to be ok. I test continuity across the three yellow wires and measured 1.1 ohms (a bit high but I’ve heard this is acceptable) When testing the ohms between the Black & White on the 6 pin connector I’ve gotten mixed readings. Sometimes it reads 36ohms and other 11ohms The connection to brushes themselves is fine. I test from the tip of the brush to the black and white wires on the 6 point connector and got 0.7 ohms.

I’ve currently ordered a replacement rotor from ricks but wanted to make sure that is the best next step and see if anyone has any ideas on if there are other test that I could preform.

Thanks for any help with this issue.

Best,
Andrew
 
Likely the rotor, the way most often fail on them. Delicate as spit and they break if you drop bike on that side for sure. They can be very bad even if the test shows to be good.
 
Thanks, that where my money is as well. I've got a new one coming in a couple of days, I think its a safe bet that its the source of the trouble, but I wanted to make sure since the rotor is relatively new and I thought I that I could be missing something. Hoping that's all it takes.
 
It can be hard to get a good rotor even new, that design is so flimsy. Literally EVERY single wrap of wire needs to be epoxied down and commonly they don't or leave the last inch of the ends unsupported by epoxy right down to the solder point. The centrifugal force then works anything loose including inside the body of wire wraps to abrade the coating to then short to other winding or to the steel rotor to make various problems. They can even break or fix repeatedly based on the rpm you are at. BTDT on one that would quit charging at over 4000 rpm, slow down and back to working again. And if you run them too long like that at some point the reg then fails because the reg senses the lost charge and ramps up the field trying to get it back to overheat to fail itself.
 
Just replaced the rotor last night and it works like a charm. At idle the bike is putting out 12.2 and quickly jumps up to 14 at around 3500. My new lithium
Ion RR is capping the voltage @ 14.3. I’ve attached a pic of the old rotor. Looks like a cheap rebuild was the source of my troubles.
IMG_4513.jpg


 
Actually I typed that wrong, I’ve got 12.9 volts at idle. Running strong. Just installed my new custom battery box for the lit ion batteryIMG_4521.jpg


 
They may barely not charge enough at idle but it should run up past break even point at past 2000 rpm or so. A normal lead acid battery is 12.3-12.8 volts.
 
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