Topic: CB 500 61mm

[Stone69er]

Hi new here,
                Im rebuilding a 1974 CB 500 motor as part of a ground up rebuild.The motor has 61
mm pistons fitted and Id like to replace or re-ring them.The pistons fitted have ART and 300 embossed on the sides by the gudgeon pins,they have a small raised dome in the middle(1 out of the 4 is different??),the valve pockets(or reliefs)look to be "machined"with a file  . I think new ones would be the go,can I use 750 pistons and maybe at 1st oversize to allow a clean up of the bore??Taking it that the pin etc all work.If not what would be the other options available.
                Also are the std valve sizes IN 27.3mm EX 22.8mm as Id like to replace these also as the tips and tappetts are showing signs of wear.Also can anyone advise or help on the matching of the bearing shells for mains and b/ends??,c/cases have 5 B,s on them and I can get the crank numbers if anyone can help.
                Any help and advise would be great,cheers Matt

[trueblue]

Have a read of this

550/650 hybrid or 650 big bore HOW TO

[Greggo]

Can you show us some pictures?  Maybe I haven't had enough coffee, but it sounds like they could be the 'Gentlemen's Express' pistons in there, right?

[Stone69er]

Ill take some pictures tonight and post them,almost time to head off to work,were early starters here in New Zealand.Can some one inform me on std valve sizes please

[turboguzzi]

yep, std valves

would first check how much sleeve thickness you have right now. stock 500 sleeves cant take 61, so these must have been changed, question is how much meat you have left for over size.

if too thin, you'll have to re-sleeve again

download the manuals, you'll find all the info on shell codes, matching, etc.

[Stone69er]

cheers Turbo