Topic: 500ccm for cb 400 four

[rudi]

Hello everybody,
I had a Question for the Experts and "Oldtimer"......
In the late 70th a Company named Action Four sells Big Bore Kits too raise the ccm from the HONDA CB 400 Four up to 500ccm.
My Question : Who knows what are the Basic Pistons for this Big Bore Kits ?
The pistons are totally flat ( like CB 500 Four ) , 13 mm Gudgeon Pin , and two small Valve Grooves.......

[robvangulik]

If you go over 466cc you need to resleeve the cylinders.

[bryanj]

Probably special cast ones.
You could get complicated and look up what models use the same wristpin circlip and see what bore those are

[Tim2005]

That's an interesting find. Have you got any photos of the pistons? That said, I strongly suspect they are specials. If there was a piston from another model that fitted I think it'd be well known by now.

And yes, as above, it'll need larger sleeves too.

[Don R]

 The 466 sounds like a handful of fun to me. I've owned three and one of those twice, but never had to take an engine apart.