Topic: Do CB650's (or 550's?) use O-rings around their cylinder sleeves?

[turkey2143]

To my horror after fuddling to put my 1980 CB650 cylinder block onto my CB650 pistons with a friend for 45 minutes (oh noooo!!!) I checked bikebandit.com's parts fiche to double check my O-ring placements to find that I am missing part 5 in this diagram, which are the 4 O-rings that appear to go around the cylinder sleeves in between the block and my 1977 CB550 crankcase:

http://www.bikebandit.com/houseofmotorcycles/1980-honda-cb650/o/m1974#sch17510

I don't remember removing these from my CB650 parts bike's engine, but my memory is a little hazy on it.

On a second look, I checked the Honda Shop Manual that this forum has a link to:


EDIT- my picture link doesn't work anymore, so here is the site link for the 650 manual:
http://cosky0.tripod.com/sitebuildercontent/sitebuilderpictures/page07-08.jpg



It mentions some oil passageway o-rings, but not these 4. They aren't even listed on bikebandit's site for sale, but they came with my CB550 rebuild kit.

I'm doing paulage's CB550/650 big bore build, sans the 750 cylinder sleeves & pistons and instead using the 650 stuff, so can anyone confirm whether or not they go on a stock CB650? It'd also be nice to know if they come on a CB550, and as well as to folks' thoughts on whether or not they are necessary, as they do not hold piston pressure like the head gasket does.

Any input is appreciated

[tomkimberly]

They are on mine. Do you need them?  I don't know.

[paulages]

They keep oil from seeping up between the sleeve and the block. Yes, the 550 and 650 both use them.