Twinstar conversion from 6v to 12v

I have a 1978 Honda CM185 Twinstar that I've been repairing and decided it would be best to convert it from 6 volts to 12 volts since 6 volt parts are getting harder and harder to find.

My question is do I need to replace the alternator? I took the starter motor and solenoid out since it's a kick start, replaced the 6v ignition coils with 12v coils, and I can easily replace the lights with 12v bulbs but I'm worried the stock alternator won't work.

I don't know enough about electonics to know for sure so if someone could offer some help that'd be fantastic.

Thanks,
rubiks

 

Of course you'll have to replace the alternator. Voltage regulator too.

If it's got an electronic ignition that would have to be replaced.

Of course all the lamps will need to be replaced.

 

Been thinking of doing the same thing to mine. Don't forget to switch the condensor from a 6 volt to a 12 volt one. I have owned mine since new and have always had trouble with it over charging the battery. From what I understand on these bikes it has no voltage regulator just a rectifier. The voltage is regulated by the draw of the headlight. I see my $65 headlight is already starting to blacken and I've only got a few hours running time since replacing it. Read in a magazine somewhere that the alternator windings on the 6 volt systems are capable of putting out higher voltages and a 12 volt regulator would be the first step. I have just started looking around to see if any other Honda 12 volt regulators have the same style of plug on them. Think I'll have to go out to the shed tomorrow and see what the one on the 400 Hawk looks like. Worth a try if a guy can round up the parts to try it cheap. If successful also opens up the possibility of updating to electronic ignition from the early 80's model. Let me know how you make out with your bike. I would also put the starter back in your bike as you don't want a open hole at the front of the engine. It won't hurt anything sitting there. If you get her switched over to 12 volts just get a 12 volt starter off ebay from a early 80's Custom or Rebel. They still use the same basic motor in the new Rebels.

 

From the little amount of research I was able to do today it looks like you could take the alternator and the regulator from a 1981-1982 Honda CM200T Twinstar and they would bolt right into the stock locations on the 185 with little altering. It seems that Honda went from the 6volt system to the 12volt some time between 1978 and 1981.

Hopefully some further digging proves that to be true. Although if I am correct you're out close to $300 just in parts to begin the process.

I did leave the starter motor physically on the bike, I just unplugged it and hid the wires.

-rubiks

 

I was looking around today too and it looks like the 80-82 parts would bolt right up. Might be some minor wiring differences to sort out but shouldn't be too bad of a job. The other option would be to hope to come across a complete 200 engine for a reasonable price and bolt her in. There was a year or two there that they had a belt final drive but I believe that is just a matter of taking off the front pulley and putting it back to a sprocket. Need to find my missing shop manual so I can compare wiring diagrams etc. Had a complete drivable bike this morning but now she's on the lift in the front room with half her parts stripped off. Want to redo a few items before spring so I can get her back on the road plus she is the only bike in the house where it's warm to work.

 

I have decided for now to just try and upgrade the 6 volt system. I have a 6 volt regulator/rectifier coming that I bought on E-bay from a 1980 Twinstar. Has 5 wires coming out of it compared to the 4 wires of the original rectifier so hopefully I can sort out the wiring and make it work. If I can get it to work it should solve the overcharging issue of the original system and not fry the battery and expensive headlight bulb.

 

I found a rather elegant solution to the expensive headlight. Not stock, but looks good, works, and is comparatively much cheaper.

http://cgi.ebay.com/ebaymotors/ws/eBayI ... 0218031838

 

Just curious as to how the transaction went as I've been a little leery of ordering from Thailand. I guess as long as they have a good feedback rating shouldn't be a problem. Any idea of what kind of wattage the bulb is compared to the original? Thanks for the tip, will keep it in mind. Also found a link to a classic VW parts supplier today that sells 6 volt H4 style halogen bulbs. All one would need is the headlight lens that accepts a H4 style bulb. Your route is cheaper though as I don't really drive mine at night anyways, just around town.
http://www.wolfsburgwest.com/cart/Detai ... D=N177621Z

 

The transition went well, actually. I'll take pictures later today and post them for you.

I've ordered a few parts from that company and in the past, aside from waiting for 3 weeks for it to arrive, I've had good exchanges with them.

 

Nevermind, camera is broken.

The headlight rim mounts straight into the mounting holes on the stock bucket and the wiring is the exact same.

The unit is shipped with a 12volt bulb but can be replaced with a 6volt bulb for a few dollars.

I'm pretty happy with it. Easy to install and extremely cheap to replace the bulb if it burns out.

 

Actually... some alternators put out upwards up 30V at speed. Your 6v alternator may not be able to keep up with everything at idle, but at cruising RPM it might be adequate.

I just had this same debate with myself after buying a '72 Honda CL100. Decided to just stick with the stock 6V system as well, using LEDs to reduce demands on the alternator at idle and adding a regulator (not equipped with one from the factory!) to keep the battery from boiling at speed.

 

acutally converting over to 12 volts is so easy. all i did was buy a 12 volt regulator/rectifer for a 12 volt twinstar and a 12 volt coil and 12 volt condesor. For the wiring of it since the 12 volt regulator had a 3rd yellow wire that that 6 volt alternator didnt was not used. i kept the 6 volt startor and soleniod which work just fine on 12 volts.

 

Here's what I did on my '78 CM185T Twinstar - NOTHING!!

My brother originally got the bike for free and it had a dead battery. He didn't know any better and bought a generic 12-volt battery and put it in. The bike blew all it's lamps, but since he'd never had it running before, he just figured that that was one of the reasons he got it for free.

He replaced the blinker and tail/brake light bulbs with generic 12-volt automotive bulbs but never replaced the headlight. Just drove it illegally only during daylight. Eventually, he moved and gave the bike to me.

I didn't know anything about it or it's history, so I just put a salvage-yard 12-volt headlight on it and new 12-volt bulbs in the dash.

I did NO OTHER CHANGES and ran the bike like that every day on my 60 mile daily commute for over 10,000 miles. It was MONTHS before I even discovered the 6-volt / 12-volt error, and by then, I didn't bother to do any further changes.

No changes whatever to alternator, starter, horn, ignition system, regulator/rectifier and, as I say, commuted those 10k miles until I eventually gave the bike back to him, and he eventually sold it off. Still running perfectly (well, as perfectly as you can expect a poor 185cc bike with 25k+ miles on it).

So, it's just a data point for you....

Kirk

BTW, the '78s and '79s were 6-volt and the '80s and '81s were 12-volt.

AFAIK, the Twinstars never came with belt drive, but the following year, the stroked and re-badged CM250 Custom DID.

That motor has been around continuously ever since. The 185 was stroked to get to 200 and stroked again to get to 250 and the 250 is still in use today, virtually unchanged, in the Rebel and Nighthawk 250s.

Great little motor...

 

If The CB125 has an alternator and not a generator, then you do not need to change it. An alternator takes a given voltage (6 or 12v) to its stator and steps up the voltage to its secondary windings. As the magnetic field (on the stator) is mechanically moved passed the secondary windings, the amount of voltage is slightly higher because there are more windings in the secondary than the primary. The output is a pulsed DC at about 14v. The faster the stator spins, the more frequent the pulses. The Rectifier is a bridge rectifier that takes the more negitive peaks of voltage and makes them positive. The reason you need to spin a certain speed before you start charging is because your pulses need to be frequent enough that the RMS voltage is higher than your supply (battery).
The condenser is a capasitor thats only job is to filter any rippling DC away from the coil. A capasitors range is stamped to it. I don't think you would need to change it because most capasitors range is very large.
The coil is the same deal. The only reason for having to change the coil is that maybe you think that 6 more volts would cause insulation brakedown on your primary coil. Your secondary coil handles thousands of volts.