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Author Topic: Cb350 64 mm pistons 812 cc information  (Read 357 times)

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Offline Turbogrimace

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Cb350 64 mm pistons 812 cc information
« on: May 29, 2024, 07:43:44 pm »
I have a set of cb350 twin pistons (64 mm) and I'm looking for some information on compression ratio and mods needed to get them to work in a cb750. The pistons are marked AP. The valve pockets are pretty substantial, and so is the dome. I recall hearing that the CR would be around 12.5 to 1 with a K head. If I could drop this closer to 11 and run a long duration cam, I think I could manage running pump gas. I'm not sure what, if any mods are needed to run these with a big cam.

Any info is much appreciated. I'm digging through my parts stash to put together some sort of big bore kit. I'm just looking for more torque for touring and some extra fun.

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« Last Edit: May 29, 2024, 07:45:34 pm by Turbogrimace »
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Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Cb350 64 mm pistons 812 cc information
« Reply #1 on: May 29, 2024, 10:32:21 pm »
The early 812 kit pistons. The dome needed cutting but I have no info on that
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Offline Old Scrambler

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Re: Cb350 64 mm pistons 812 cc information
« Reply #2 on: May 30, 2024, 07:10:30 am »
Run them with an F2-3 head and somewhat mild cam..........

or install a double or triple base-gasket and a thicker MLS or copper head-gasket. Be sure to install cam 'straight up' ;) Measure carefully.
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Offline Dresda500

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Re: Cb350 64 mm pistons 812 cc information
« Reply #3 on: June 17, 2024, 02:32:02 pm »
The CB350 had 34mm Int and 28mm exh valves stock so had sizable reliefs
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Offline johno

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Re: Cb350 64 mm pistons 812 cc information
« Reply #4 on: June 20, 2024, 01:38:59 am »
Hi Turbo,
Check out a forum posting by Mick, titled "CB900 rods in a CB750"
Its got all the goss you will need and more.
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