I am midway through a rebuild on my 87 600F. I found some o-rings around the cylinders that were not in my OEM gasket kit.

Part #8in this link:
http://fiche.ronayers.com/Index.cfm/...Group/CYLINDER

My local machine shop and engine builder says they are unnecessary.

If anyone has any experiece with these I would appreciate some feedback.
Engine is in pieces and ready for re-assembly except for this. 4 days plus from Hondaand I don't wanna wait. The old ones are not re-usable due to swelling from parts washer solvent.

Thanks.

 

My genuine Honda top end rebuild kit didn't include them either. No idea what they do... but Honda OEM manual says check them for damage or fatigue (presumably replace), Clymer manual says replace if worn or deteriorated, & Haynes manual ignores them. IMO, considering the time & cost of a rebuild, I'd say its worth 4 days' wait to fit replacement ones, just in case. Can't see why Honda would fit them if they aren't necessary.

Looking forward to other opinions on what these o-rings do & whether they should be left out!

 

I agree about the "time and cost of rebuild" being sufficient to wait for the o-rings.....at least that was my first reaction. If they are truely needed and not in the gasket kit I am gonna have a bone to pick with Honda ( 1st time ever ).

 

Gearloose,
I take it you did install them in the end eh?

 

Mine were OK - I hope. I sent the cylinder block (I hadn't removed the O-rings - thought I might damage them if I did) to an engine shop and they cleaned it and deglazed the bores (also did work on the head). O-rings looked the same when it returned. Bike's done about 3k (giving it gyp, not commuting) since then and hasn't fallen apart. So I think they are OK. Will ask the engine reconditioner what they are for next week. Can't find anything on internet.

 

The rebuilder of my engine said:
[ul][*]the O-rings are there as backup to the gasketed joint between the block and crankcase. They are an added measure to stop oil seeping through the joint to the outside of the engine;[*]this sort of seal is not particularly common, but not that uncommon either. It is one of the methods used by Japanese engine manufacturers to minimise oil leaks. Sort of competitive advantage over road-oilers of the time;[*]the O-rings are normally a special profile: thin section, and special size. There's usually no alternate generic replacement. Replacing them with standard O-rings usually results in failure (either not sealing, or distorting the barrels and causing the barrel to tighten on the piston at that location);[*]He advises against removing them if undamaged. You do not have to replace them if damaged, but it increases the possibility of oil seepage at cylinder/crankcase joint.[/ul]
Howzat! Gogar & Michigan_313 - you guys got any comments on the above?

 

Thanks for putting so much effort into finding an answer. Since they (o-rings) are already on the way I guess I will wait till Friday to assemble. Maybe I will exclude on the next rebuild just to see what happens.
Thanks again.

 

sounds legit to me. i have spare engine at home but i don't remember seeing them. i may have to look again it's been so long.

but i do think that if the manufacturer put them in to begin with, they should go back in for the rebuild as an added measure of confidence. you already are putting so much time and effort into it, why skimp now? honda, in general, engineers some pretty good stuff. if it wasn't necessary, they wouldn't have done it. plus, you gotta remember this was hi-tech almost 25 years ago. these days you can get away with the fancy-shmanshy nitrogen filled bi-metal copper hi-tech who-knows-what's-in-there gaskets. but since there probably aren't any applications for this engine, you just gotta go oem.

my original engine (90,000k+) has not gone through a rebuild and i don't see any seepage from the block/crankcase area. so far, so good.