C90Club.co.uk

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

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

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

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.





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

steve g

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.

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

viewtopic.php?f=43&t=25040

steve g

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

Steve g, thanks for the big valve link, can you tell me if all big valve heads are bi metal, its just i looked at my spare c70 motor, its an early one with a downdraught carb, the head is not bi metal but the valves are marked with 7's not 7's in circles, the top of the inlet valve measures 26.45mm, thats accross the top in situ, so is it a big valve one?
Many thanks.

Apologies, they are 25 and 22mm not as i said before.

Most but not all the bi-metal big valve 70 heads i have had were from the early downdraft carb models. Think some may have been swapped for later 6v heads or ones from the ATC70 engines. Have had a lot of good fast engine builds using the smaller of the 2 big valve heads,work best with a good fast road cam. One non bi-metal head i had that took the bigger valves was from a CT70H engine.

steve g