Topic: cb750 piston # question

[muddykart04]

hey guys, i have a stupid question. im doing a top end in my 76' 750 my verneer caliper measures 2.490" ( it isnt perfectely accurate either hence the stupid plastic ones )

honda states that std. bore is 2.480 but..... i think my pistons in the bike are .15 over The ###'s on the pistons read
15  300  HONDA.  do i have my info correct? What size piston rings should i order? any prefered manufacturers?? thanks

also upon tear down i noticed that the two of the main oil passageways between cylinders 1/2 and 2/4 on the back side of the motor were 1/3 full of sand!!! i never have been in any sandy place or took neglegant care of the bike howw did it get there?? ( the bike was given to me after sitting for 15 years)

[muddykart04]

so.... anybody have some imput here??? it would be muchly appreciated

[City Boy]

Hi there.The sand sounds scary but since you are tearing it down and don't know the previous history,don't sweat it but do a thorough job of cleaning and inspecting for wear.Honda pistons come in 4 oversizes for the sohc's,.25mm-.50-.75-and1.00mm.The oversize # will be stamped on the top of the piston if OEM.    Rock On

[crazypj]

You would be better off with an accurate steel rule marked in mm.
The cheap ( $2.00~$5.00) plastic Vernier calipers are only useful to explain how they work when teaching.
(Vernier scale was invented by Pierre Vernier in 1631)
 Harbor Freight Tools has electronic calipers for less than $20.00, they are accurate to 0.0005" or 0.001mm (I checked)
 Battery life is a bit short though, I find new battery needed every month/six weeks (so I've got back to 'real' Vernier calipers)
PJ