6v to 12v HELP NEEDED PLEASE!

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willmc
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Joined: Mon Sep 14, 2020 5:00 pm
Rides:: Honda ST70

6v to 12v HELP NEEDED PLEASE!

Post by willmc » Wed Oct 13, 2021 11:59 am

Sorry all I have posted this in the past but have done some extra research and feel like I need more help.

Has anyone done the 6v to 12v conversion? I have an ST70 I want to convert.

I am now reading I would need to change the crank, stator and flywheel? Is this correct? Only with other parts listed on my previous post.

Has anyone out there done this? Need help bad, thank you!

loadedtoad
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Re: 6v to 12v HELP NEEDED PLEASE!

Post by loadedtoad » Wed Oct 13, 2021 9:03 pm

As your research has correctly suggested fitting a later 12 Volt stator plate is quite involved and expensive especially if you have a good running 6 Volt engine.
Unfortunately the 12 Volt lighting and charge coil is a different footprint to the 6 Volt so cannot be directly exchanged.
If all you want is 12 Volt lighting and charging the cheapest route i expect is to have your lighting/charging coil rewound to the 12 Volt specification
Not a DIY job unless you are experienced but there are plenty of motor rewind companies out there.
Get hold of a used 12 Volt Lighting coil of ebay etc and take your 6 Volt coil to a rewinding company and say make my 6 volt coil the same as this 12 volt one.
If i had to guess It's probably a simple matter of twice the amount of windings with copper wire half the thickness but i'd prefer to dismantle a known good unit to be sure.

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steveST100
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Re: 6v to 12v HELP NEEDED PLEASE!

Post by steveST100 » Wed Oct 13, 2021 10:07 pm

Another way of doing the 6v to 12v is to find a old Jincheng m50 or DX90 plate and flywheel as these are 12v but the cranks have the 6v taper on them.
Not easy to come across now as they were 15+ years ago. Lot were used in monkey and Dax bikes to make them 12v.
You do have to do a bit of grinding to fit the cdi pick up on the crankcases, but not as much as fitting the 12v cub plate to the 6v engine cases. Also think you have to fit the 12v flywheel cover as the flywheels are deeper on the 12v ones.
If you can get the DX90/110 early engine the crank is the same throw as a c90 and will make your 6v ST70 a 85cc or bigger when fitted with the longer studs and cam chain of the 90/110 engine. The 6v cases can be modded to take the bigger 90/110 or TRX90 oil pump.

steve g

cozi70
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Re: 6v to 12v HELP NEEDED PLEASE!

Post by cozi70 » Thu Oct 14, 2021 7:53 am

In relation to the jinger/easy rider 6v/12v flywheel and stator availability new, I contacted shire bikes recently and they can no longer supply either of the parts now.

Regarding the long and short crank shaft situation, which of the 6v engines are long. Is it just down to the original setup having advance and retard, like a c70, as I've an ss50 engine 12v converted but recently found the z50 engine to be short?

willmc
Posts: 10
Joined: Mon Sep 14, 2020 5:00 pm
Rides:: Honda ST70

Re: 6v to 12v HELP NEEDED PLEASE!

Post by willmc » Fri Oct 15, 2021 1:03 pm

Thanks for the response all.

To confirm I only want to have the 12v to make the ST70 easier to start up, greater voltage would make it easier and then of course in term improve the strength of lights etc.

So if I only want to achieve the above in terms of better start up what would you recommend I change? Is it just basic electrical conversion?

Let me know what you guys think, thank you.

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wightegi
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Re: 6v to 12v HELP NEEDED PLEASE!

Post by wightegi » Fri Oct 15, 2021 1:21 pm

The voltage will not make it easier to start , the 6 volt 70 and 12volt bikes do not need the battery to start and run off the stator. If it is hrad to start I would look at the wiring and any joints and also check the compression and timing, ignition and cam.

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