Rectifier Regulator for CT90 and SL100

H

Honda Hornet

Member
I have a 1978 CT90 and a 1972 SL100 and only one silicon rectifier. Moreover, I often ride 100 mile trips at close to full throttle and find that the battery has lost water when I get done. If I could get a regulator that will limit the high voltage, but allow power to pass as needed for ignition and lights. I tried to buy one on eBay, but it does not allow enough power to maintain the battery at high revs with headlight. Apparently, this was because it was intended to work with an AC headlight (although both bikes have DC headlight).
 
H

Honda Hornet

Member
Can anyone recommend a rectifier regulator that will limit DC, but only when the voltage gets too high (i.e., not being used by lights and ignition), rather than always limiting power? Obviously, for a 6V system.
 
H

Honda Hornet

Member
Curiously, mySL100 has a vintage 12V headlight and it does not seem to work well, but I might test more. On the CT90 I was able to add the front signal lights as running lights to lower max voltage to 7.2V, and the battery serms happy. I switch it off for stop and go in the city, but it makes the longer high RPM rides okay. Fixing the issue with electronics seems like a better answer, but it seems there are none available. Most sellers on eBay offering rectifier regulators for 6V just ignore my questions.
 
B

b52bombardier1

Well-Known Member
The rectifier is NOT meant to be a voltage regulator on these 90 CC bikes. Rather, the overall vehicle lighting on the bike is meant to consume the power produced in the stator to a normal level.

Rick
 
H

Honda Hornet

Member
I know that Honda did not include a regulator originally, but I also think it is pretty well known that relying on matching load and overcharging the battery as the regulation is not ideal. I am looking for a replacement part that does more than original equipment. I doubt I am the first, so if you have had success, please let me know.
 
OldGuy

OldGuy

New Member
Just thinking about the use of a 12v bulb... This would NOT consume more current on the 6v battery system. In fact the 12v bulb would have roughly 4 x the resistance of a similar wattage 6v bulb. It would draw about half the current, and thus allow the 6v system to run higher than normal. It also would have much less brightness. Resistance/current draw on an incandescent bulb varies with heat/brightness, so the calculations are more complicated than simple ohm's law, so this comment is only an estimate.
My '66 CM90 now has a silicon rectifier and the voltage is higher than original. With the daytime headlight laws and the extra headlight winding active in the generator full time, it seems to be OK, but battery life is still only 1-2 yrs.
 
J

joel1234567

Active Member
Battery water loss after extended wot trips is normal.

PardueBrothers used to have a regulator like you describe. I used it on a ct70 with an aftermarket coil that was putting out too much voltage and it worked well to keep the bulbs from popping. It was a beast tho, great big thing that filled the whole headlight bucket.
 
H

Honda Hornet

Member
Did the Pardue Brothers regulator have a large heatsink or just large enclosed components. I have looked at options to make one for myself, as I have not been able to find one already being made.
 
J

joel1234567

Active Member
I think i misspoke here after looking back thru my records at what it was. It was specifically a pardue brothers headlight voltage regulator, not a whole battery regulator, specifically for taming ac voltage headed to the headlight. Not what youre looking for. Sorry about that.
 
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