C90 into st70

A place for Monkey Bike and Mini Bike (including Grom/MSX) enthusiasts. This will be moderated in accordance with C90Club rules. Welcome!
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Sparky_col
Posts: 3
Joined: Tue May 14, 2019 5:27 pm
Rides:: St70

C90 into st70

Post by Sparky_col » Thu May 23, 2019 8:31 pm

Hi all,
Anyone advise on any problems doing the above, its a 6v c90 engine.
Many thanks.

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wightegi
Posts: 7462
Joined: Tue Sep 01, 2009 7:23 pm
Rides:: 12v 1988 e start C90, Gl5oo silverwing ,suzuki GS500F
Location: Isle of Wight

Re: C90 into st70

Post by wightegi » Thu May 23, 2019 8:38 pm

50 and 70 engines are the sane size as the 12 volt 90 , the 6 volt 90 will not fit in these frames , the big valve C70 bike is faster than the 6 volt 90 one ;)

Sparky_col
Posts: 3
Joined: Tue May 14, 2019 5:27 pm
Rides:: St70

Re: C90 into st70

Post by Sparky_col » Thu May 23, 2019 9:16 pm

Thanks, next question is where can i get a big valve head, anyone know?
Thanks again.

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steveST100
Posts: 1640
Joined: Tue Oct 25, 2011 3:04 pm
Rides:: 1983 C50LAC 1976 ST100 1980 ST70
Location: Clitheroe Lancs

Re: C90 into st70

Post by steveST100 » Thu May 23, 2019 10:16 pm

Yes it can be done.
Lot of work and some cutting of the frame to fit it.
Will be a pain to do the wiring.

Image

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Stick to the 6v 50/70 and 12v 50/70/90/110/125 for it.

steve g

Sparky_col
Posts: 3
Joined: Tue May 14, 2019 5:27 pm
Rides:: St70

Re: C90 into st70

Post by Sparky_col » Fri May 24, 2019 7:44 pm

Thanks for that info, i want to keep my bike as original as possible so i really dont want to cut the frame, i will hunt for a c70 head, i understand its pre 79 bikes that had them, any pointers towards one would be gratefully received.

User avatar
steveST100
Posts: 1640
Joined: Tue Oct 25, 2011 3:04 pm
Rides:: 1983 C50LAC 1976 ST100 1980 ST70
Location: Clitheroe Lancs

Re: C90 into st70

Post by steveST100 » Fri May 24, 2019 8:17 pm

Bit i did in the guides on the big valve heads.

viewtopic.php?f=43&t=25040

steve g

Barnsey
Posts: 92
Joined: Fri Aug 11, 2017 12:31 pm
Rides:: Honda C50 BMW R100
Location: Portsmouth, Hampshire

Re: C90 into st70

Post by Barnsey » Thu Jun 06, 2019 2:09 pm

Check this out:

Ebay part number 322387613092 .

I ordered one of these, and I was relieved that it bolted straight onto my 1973 C50 engine. I just can't say how well it runs as I haven't started it yet.

Regards,

Ian

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