Is this a standard piston?

[TonUp]

Popped the head off my CB550F2 to fit new cam chain and tensioner. My mates were curious to know if these are standard Honda pistons or first oversize or pattern? Any engine experts on the forum?

The bike has done 58,000 miles and I have been told that the bores look like they have been honed. Also the bores are in perfect as new condition "like a new bike, less than 10,000 mile".

[Bryanj]

Pistons are not always marked with size but rings are if you take them off.

Alternatively just get a set of vernier calipers and measure the bore.

With the head off i have found that the cylinder always moves and unless changed the base gasket/O rings will leak later

[Trigger]

Look Original Honda due to the arrow on top of the piston. Pattern piston's don't always have the indication arrow. Looks too clean for 58.000 miles. Pop the barrels off and that should give you more of a clue, and as Bryan has stated: once the head has been disturbed you will have to replace the O'rings and base gasket.

[TonUp]

Thanks for info. I will do the base gasket as well, good job I posted on here.

[Bryanj]

HINT:-

Leave the base locating dowels that have the oil restrictor in place whilst you clean off the old gasket as a bit of old gasket down the oil feed gallery will wreck the top end and its ever so easy to remover the dowels and clean the jets just before assembly

[TonUp]

Thanks for the info about cleaning old gasket off.

The original tensioner is broken, moving the blade does not move the screw. The nut was seized onto the adjustment bolt too. Had to drill and dremel the nut off.
On the plus side - I did get £150 refund from the motorcycle dealer that sold me the Honda.

One of my mates has taken the head away to de- coke and re seat the valves. He says that there is no wear on the stems at all, just like new.
Some low life broke into his garage the same evening that he took my head. Power tools stolen but thankfully the head was not touched.