CB750 sohc F2

[archmill]

Got the pistons ready for fitting ( ring gaps checked, pistons cleaned ) and noticed I had not marked them front and back.
Do the pistons have a front and back ? or does it not matter.
Anybody know ?

[Johnwebley]

Normally a small arrow on the crown

With the size

Looks like a small triangle

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[Bryanj]

Yes it matters and should be marked if genuine

[archmill]

[ Guests cannot view attachments ] no arrows guys but the pistons have an indented circle on them. Assume this is front ?

[K2-K6]

Could be wrong, but some details on that piston appear odd against what I recall as normal.

Looks like .... the top valve clearance "pocket" has been recut, with evidence of original visible near to edge, then another pocket located inwrads.

Is there some bits missing from ring land at about 2 o'clock  ? Those little triangle marks, or just carbon and indented  ?

The turning finish is quite "rudimentary" especially in the centre, and makes them look like a modified piston possibly.

The official Honda manual for F2 indicates to put the "offset  "O" mark on piston faces to exhaust side  (forward)" quoted directly, it gives a picture of the O location consistent with your piston too. But if you're really unsure, then assembly with representative gasket and use plasticine to check valve pocket clearance by rotation of crank would be definitive in assessing them.

[archmill]

Thanks K2-K6, answers my original question as to whats the front of the piston.
I don't think the top pocket has been re-cut, I think a valve has been hitting it.
Yup, the small triangles at 2 o'clock are just small dents with carbon, not anywhere the ring land.
Pistons could have been turned as the valves I took out did not match and I recon it either dropped a valve at some time or a valve head decided to part company with the stem and possibly someone cleaned the damage on the piston top.
I am fitting brand new valves from Cyclex in the USA and had to replace one of the liners which had a big gouge out of the side wall, funnily enough the shape of a valve edge.
I will indeed take onboard your suggestion with the plasticene. Going to re-build everything without torquing the head down and look at the valve clearances.
Again, many thanks for your advice.

[K2-K6]

A bit of a fraught existence then for the engine in previous ownership 

Hopefully you get all the details sorted and back to more cohesive running.