1979 Honda CM185T 12 Volt Conversion

tatters · Exxon Valdez Joined: 05 Jan 2004 Karma :

A few years ago myself and my brother-in-law found a 1979 Honda CM185 Twinstar in a barn that had been sitting since 1993. Bike is in very good condition with only 4500 miles on the clocks.

Brother-in-law is looking for a small light bike to carry on the back of his motorhome so we have decided to get the little Honda on the road.

I am currently doing all the normal stuff like new tires/carb clean/oil change etc. The bike currently uses a 6v electrical system and 6v batteries are hard to come by in my part of the world.

I am planning to use a 12v battery and replace the 6v rectifier/regulator along with the ignition coil and lamps with 12v ones.

I cant seem to find any more solid information on other forums but does any one know if the existing stator will work with a 12V rectifier/regulator. Also will the change in voltage effect the points?

https://www.bikechatforums.com/files/tatters_cm185t.jpg
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Past:NRG50,AF1125(x2),NSR125RR,ZZR250,CX500,VFR400,KR1S,ZZR600(x2),CB400N,YZF1000(x2),KH125,Z200,FX400R,CBR954RR(x2)GPZ500S,GT550,VFR750F(x2),RD350N,XR650R,CBR600F,CB250,KDX250,YZF750R,CRM250,400EXC,KLR650,TTR600RE,DR350S,R100GSPD,RGV250,VMAX1200,DL650 Present:G650XC,C12,KZ750,1190ADV

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

It'll have the same power output, so more volts, fewer amps. Cables will all be thick enough because they will be carrying half the amps.

The points will be ok, the condenser might not.

Also flasher relay, horn and Possibly any diodes that may be fitted. Ballast resistor if it's direct lighting.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

WD Forte · World Chat Champion Joined: 17 Jun 2010 Karma :

You really need to examine the stator first, everything else is pretty easy.
12v bikes run at closer to 14V than 12V and have a stator output well in excess of 14V in order to get a consistent supply and keep the battery charged.
The CM 185 stator looks a simple affair and I reckon could easily be rewound to give a higher voltage output if needed
Any voltage under 13v is doing nothing useful.

The limited power output can be dealt with by using led lamps
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tatters · Exxon Valdez Joined: 05 Jan 2004 Karma :

So l ended up replacing the 6v rectifier with a 12v rectifier/regulator off amazon along with replacing all lamps to 12v and the ignition coil with a spare l had from a KZ750.

Starter motor is still 6V along with the horn and condenser plus starter solenoid. And the stator was never change/rewound.

Bike runs perfectly and l am getting 14 volts when engine RPM is increased. Thumbs Up

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Past:NRG50,AF1125(x2),NSR125RR,ZZR250,CX500,VFR400,KR1S,ZZR600(x2),CB400N,YZF1000(x2),KH125,Z200,FX400R,CBR954RR(x2)GPZ500S,GT550,VFR750F(x2),RD350N,XR650R,CBR600F,CB250,KDX250,YZF750R,CRM250,400EXC,KLR650,TTR600RE,DR350S,R100GSPD,RGV250,VMAX1200,DL650 Present:G650XC,C12,KZ750,1190ADV

blurredman · World Chat Champion Joined: 18 Sep 2010 Karma :

I'm curious.

What RPM are you doing when the 14v kicks in?

So the battery is still 6v I take it in order to power the horn and starter motor (although i'd also think the brake light (not the 5w tail though) is most likely DC (although I suppose you could have rewired it for both filaments to be AC) - so how do you then step that 14v to 7v down again for the battery? Have the original regulator alongside the 12v one to step it down again just before battery? Question

I'm just curious that's all Cool

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CBT: 12/06/10, Theory: 22/09/10, Module 1: 09/11/10, Module 2: 19/01/11
Past: 1991 Honda CG125BR-J, 1992 (1980) Honda XL125S, 1996 Kawasaki GPZ500S.
Current: 1981 Honda CX500B - 91k, 1987 MZ ETZ250 (bored to 295cc) - 38k, 1990 MZ ETZ251 - 49k, 1979 Suzuki TS185ER - 9k, 1972 MZ ES250/2 - 17k.

tatters · Exxon Valdez Joined: 05 Jan 2004 Karma :

blurredman · World Chat Champion Joined: 18 Sep 2010 Karma :

Thanks for sharing Cool

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CBT: 12/06/10, Theory: 22/09/10, Module 1: 09/11/10, Module 2: 19/01/11
Past: 1991 Honda CG125BR-J, 1992 (1980) Honda XL125S, 1996 Kawasaki GPZ500S.
Current: 1981 Honda CX500B - 91k, 1987 MZ ETZ250 (bored to 295cc) - 38k, 1990 MZ ETZ251 - 49k, 1979 Suzuki TS185ER - 9k, 1972 MZ ES250/2 - 17k.