• There has been a recent cluster of spammers accessing BARFer accounts and posting spam. To safeguard your account, please consider changing your password. It would be even better to take the additional step of enabling 2 Factor Authentication (2FA) on your BARF account. Read more here.

CT90 12 volts conversion

musiclucho

musiclucho

Zombie
Joined
Jan 15, 2018
Location
Delano
Moto(s)
Honda CBR900RR
Honda Nighthawk
Name
Gabriel
Howdy all,

Two days ago I decided to pull the trigger on an old Honda for my wife to ride in town. I tried before 250cc but she felt intimidated. No clutch and smaller cc, power and less weight seems the right way to do for her (for now…bua ha ha ha)

Anyways, bike barely runs and one thing bothers me is the original 6 volts system. I have experience in the past of batteries dying all the time because not enough juice to light all the lights (running lights, turn signals, horn, and speedo lights) and still charge the battery.

Anyone has done it? Any advice?
Another idea is to switch everything to LEDs and keep and bike and a trickle charger. Would that be better?

Thanks. I will post updates as I go along this issue.
 
If you can get 6 volt LED’s, you might try keeping it as a 6 volt system. Id try that first over the expense of converting it to 12 volts. The biggest part of the cost of converting to 12 volts might be the alternator. I dont know if the current alternator puts out enough voltage to run a 12 volt vrr and system.
 
And do a google search for Honda CT90 conversion 12 to see other’s efforts in that area.
 
The old CT90 and other small Honda 6 volt bikes were a "balanced" charging system where the output of the charging system matched (slightly exceeded) the drain of ignition, lights etc. so the battery would always remain well charged but not excessively overcharged during normal operation despite lack of a voltage regulator. When the wiring connections are clean and the battery is healthy these systems work just fine. If they didn't there would not have been over 100 million Honda 50 Super Cubs sold worldwide since 1958. But with corroded connectors, bad grounds, deteriorated batteries and sitting at stop lights for extended periods with the high wattage brake light illuminated, voltage can drop too low to power the ignition coil. Bottom line is the 6V systems work just fine if in good shape, but likewise 12V systems also only work well if all components are in good shape. 12V systems are stronger but the conversion requires change of stator, rectifier, battery, ignition coil, light bulbs and horn so they are an expensive solution to a non-problem if the stock 6V system is up to par.

-Bill
 
ST Guy:
Thanks for your reply buddy. I have been googling and trying to find YouTube videos but nothing really concrete…so far. I just saw a guy that upgraded the rectifier and bunch of others that have changed the whole engine. I will keep looking….

Bill:
I just came from a video that explains what you tell me. Just enough current to maintain the system. I will start with cleaning all connections and see if that helps to keep the battery. I have done a parasitic test but plan to do it soon. Will keep posted…
 
musiclucho, one other bit of information. The 6V charging systems had 6 coils in the stator. With the headlight off, only two of the coils were connected which put out enough power for ignition and occasional blinkers, horn etc. With the headlight switch in the ON position it added the additional 4 coils to increase the charging current to also supply the headlight and taillight. So a faulty headlight ON/Off switch can cause low charging current if it does not add in the extra coils.

-Bill
 
Since these simple systems lack voltage regulators the charging output is designed to match the loads, so reducing the wattage too far leaves excessive charging output which can burn out bulbs and overcharge the battery.

-Bill
 
Howdy,

Some updates on my electrical nightmare lol. I got it running with the current battery (after I charged it with my 12 volts connected to some bulbs used as resistors) and the rectifier (regulator?). This last one was corroded and when I cleaned it, one of the legs broke off but I re-soldered just to make the bike run.

I ordered a new rectifier on eBay (it is a solid “heavy duty” made by braintarp) and a 6V Yuasa. Bike kicks and runs easy but lights are still weak even with full battery. I found out that hi beam is not working so I always turn the bike with no headlight (I don’t have an on off switch for the light so they are always on). Today I found out the culprit of the hi beam was the switch and I fixed it but in the process I tried the switch the battery 4 or 5 times less than 10 seconds and now the battery is discharged at 5.6 volts or so. Of course bike is hard to start again. Placed charger (I got a dedicated 6 volts) and see.

Here my questions. Bike on and running, I check voltage on the bike and is merely 6 volts even revving that sucker up (could it be that the charging system is not working or the bike drawing too much front the battery? How to individually test that?) Battery charge 6.5 but with switch on, goes down to 5.6. Stop light and neutral are on all the time. Is that normal to have such low voltage (again, seems like the bike is sucking down the volts).

Thanks for your input. Please ask as many questions as you consider appropriate. English is not my first language so some times I feel like I might not explain myself well enough.
 
For all your various checks, just half the voltages of a 12 volt system. For instance a full charge on a new battery would be half of 12.8 volts: 6.4 volts. The charging system should put out half of 14.4 volts or so: 7.2 volts or so. A used battery at full charge would’ve around 6.25 volts. Half of 12.5 volts.
 
And your reading of 6 charging volts is equivalent to 12.0 volts in a 12 volt system. You need closer to 6.9 volts. Equivalent to 13.8 volts in a 12 volt system.
 
You must log in or register to reply here.
Back
Top