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6volt to 12volt conversion

Posted: Sun Jun 23, 2019 12:10 am
by IronTom
I have a 2-cycle 79cc Yamaha scooter engine-2-wheel 'unit', with two spring-loaded brackets which were cut from the original frame.
The plan is to adapt this complete assembly into a small 1959? PUCH scooter made in Austria.
( You may remember Sears&Roebuck sold Allstate mopeds & scooters. )

According to Google, the Yamaha thing was a Riva CV80k, or maybe a Beluga CV80.
The swingarm is stamped 3T-00 1231. The exhaust is the 'bota-bag' style.
The old carburetor and oil injection pump will not be used.

Question :?: Six-volt AC or DC CDI ?
Of all the Google wiring diagrams,,, none match this engine.

We have five wires from the flywheel:
Black #1 is battery negative, grounded to the engine.
White #2 is AC voltage approx 5-8v.
White/red #3 freaks my cheapo-meter. Suspect it is the CDI 'pulser'.
Yellow #4 is AC voltage approx 5-8v.
Black/red #5 is zero. Suspect it is the CDI 'pulser'.

Since there are two pulser wires, we assume the Yamaha CDI is AC, and does not require a battery for ignition.

We bench-tested a 12v (5-pin) AC CDI but the pulser will not trigger a spark. The AC voltage is too low.
A 12v (4-pin) DC CDI is on order. It connects direct to the 12v battery.

Question :?: Has anyone converted the 6v Yamaha(Japan) to 12v CDI(China) ?
Your advice is welcomed.

Re: 6volt to 12volt conversion

Posted: Sun Jun 23, 2019 4:56 am
by flybd5_juan
The CV80k has a magneto CDI. I suggest you sit down with a large cup of coffee and read the service manual. :) ... Manual.pdf

Re: 6volt to 12volt conversion

Posted: Mon Jun 24, 2019 4:18 pm
by IronTom
I typed out a long narrative on this topic.... but it asked for my signon ??? which discarded everything I had typed.
( this automatic sign/on works just like the Yamaha rev-limiter, if you dont go fast, it shuts you off ! )

Anyway...... thanks for the most-correct manual.
More to follow... maybe.....

Re: 6volt to 12volt conversion

Posted: Fri Jul 26, 2019 12:25 pm
by Dan Durston
I used to have a CV80 and found the 6v electrical system highly problematic (e.g. the headlight would dim when the blinker blinked) but instead of switching to 12V, I made it more efficient by using LED bulbs everywhere. I didn't switch everything (e.g. headlight) but I switched the blinkers, tail light etc which made the scooter a lot better. There's more info on this if you search over at

Re: 6volt to 12volt conversion

Posted: Sat Jul 27, 2019 12:23 pm
by flybd5_juan
Switching to LED bulbs is an excellent idea.

Re: 6volt to 12volt conversion

Posted: Fri Oct 25, 2019 2:33 am
by Madhurigore
Here are some of 6V to 12V DC converter circuits that can be used to convert a small voltage of about 6 volts to a higher voltage of 12 volts but ofcourse with a lower current rating. ... This inverter circuit can provide up to 800mA of 12V power from a 6V supply.