Topic: mic'ing pistons

[wadarush]

I'm helping a buddy of mine build his cb550 motor and we've come across a little confusion while inspecting for wear.  In the manual it says that the piston diameter serviceable limit is 2.302in.  I measured each piston in two different locations above the first ring groove and got consistent measurements in the 2.283 region....  What gives?  Am I measuring in the wrong spot on the piston or have all the pistons worn evenly and need to be replaced?  The cylinder bores checked out to be ok so that adds to the confusion. 

[mark]

Measure the other end. You should get different numbers when the pin bore is straightways/crossways as the pistons are not round when cold.


Happy trails.

[Jinxracing]

Found this:

http://www.kb-silvolite.com/feature.php?action=read&F_id=27

and this:

http://www.dansmc.com/pistons.htm

[754]

Bottom of piston skirt @ 90 degrees to the pin bore..

[bryanj]

Pistons are always measured on the skirt not the ring lands and if there are no siezure marks I will be amazed if they are below limit as Hondas just dont seem to wear, More important is ring gap in the bore and that isnt often outside limits, ive had 120,000 mile old 750 with pistons, rings and bores all inside limits!!