Honda-SOHC

SOHC.co.uk Forums => CB750 => Topic started by: whiteylfc on February 20, 2020, 08:36:03 PM

Title: F2 big bore piston
Post by: whiteylfc on February 20, 2020, 08:36:03 PM

I stripped down a cb750 f2 engine i bought off ebay last yesr and found this piston hiding inside the engine block..its marked as a Honda but is very different to a standard f2 piston and a much higher crown and bigger valve cut outs.its looking like it's had a big bore conversion but I'd appreciate if someone can identify it..

Title: Re: F2 big bore piston
Post by: Bryanj on February 20, 2020, 08:57:12 PM

Measure the bore, F2 pistons do have a big dome and cuttouts(for the bigger valves)

Title: Re: F2 big bore piston
Post by: whiteylfc on February 21, 2020, 01:33:16 PM

Side by side the piston on the left is way bigger...the left one has a 64mm diameter.the right one,a standard f2 piston has a 61mm diameter.the displacement should be 812cc.I just wondered if one of the boffins on this site would know the origin of these piston with them being a Honda item...

Title: Re: F2 big bore piston
Post by: K2-K6 on February 21, 2020, 02:58:09 PM

Recollection is that the 64.0 mm piston was from cb350 Honda twin engine?

Cursory looking via search seems to confirm this,  also thought that made them 836 cc as used in general "big bore" kits.

Additionally,  thought that Yoshimura used sizing to make 812cc,  possibly with bespoke pistons.

All subject to other confirmation  :)