Topic: Down to base gasket, unsure of next move. [pics]

[Papa-wheelie]

I'm replacing leaking gaskets on a 1981 CB650 on a bike I recently purchased.  The bike ran/drove fine but leaked.  I intended on only replacing leaking gaskets but now am unsure of the condition of the piston and rings.  Lots of carbon buildup on top of piston but bike ran fine before tear down [ other than the leak], no smoke from exhaust and ran smooth.

Questions:

1.) Can/should piston be cleaned or replaced before re-install?

2.) Do rings need to be replaced?

3.) Any recommendations on gasket kits?   Are the cheaper Athena kits on Ebay okay to use?

Any tips on reinstalling this would be appreciated.  Previous owner failed to clean grit from head bolts before removing them prior to him replacing the gaskets and as a result the gaskets leaked due to poor torque settings.  Plus now I've got to figure out how to get the grit out from the bottom bolt holes before I put the head bolts back in since there is grit in them.

Again, any advice is appreciated.

Papa-wheelie

[dave500]

making sure every thing goes back where it came from id pull the pistons to clean them your this far into it now,carefully remove the oil rings and clear the lube holes,those are normally 1mm.check the ring gaps in the bores and if ok then keep the rings,loosen that grit poking with wire then just use compressed air to blow it out,cover any where you don't want grit landing in like open cases etc.

[Bodi]

Since it ran well before disassembly without smoking, I would avoid fiddling with the rings. Getting them out to check gap then getting them back in risks breakage - that metal is very brittle.
The piston crown and combustion chamber (not shown but this usually matches the piston tops) carbon is not very bad, it will look the same fairly soon if you get them spotless before riding again. You can use a fine steel brush to get it off if you want. Pack rags around the rods to keep crap out of the block, clean the pistons really well afterward - brake cleaner spray around the rings will wash the grooves out as well as possible.
Removing the pistons is OK but you should always use new pin retainers on assembly.
A very light hone of the bores won't hurt, and removes any carbon buildup above the top ring. If you really feel new rings are desirable you need a fairly aggressive hone to get a crosshatch that will seat them.

[TwoTired]

I'm a minimalist.  If your intention is to street ride instead of getting max race potential, I'd just de-coke the piston tops and chambers to get out any major build up that would change compression, and then go ahead with your original plan of fixing leaks.  As long as the rings and pistons are still married and seated to the bores, keep them that way, and don't remove any more metal from either.  Honing will remove metal from both, giving you the opportunity to take it apart again sooner and replace components.

That's what I would do, anyway.  Kinda depends on how much tinkering you want to get into.  I don't buy the "while-you're-in-there-do-more" approach for normal machine operation.   Honda built engines way better than any rookie mechanic, imo.

Cheers,

[Don R]

 I have to lean towards what TT said. Projects tend to get out of hand, next thing you know you'll be boring out and spending $$.  If you're leaving the rings, leave the cylinder as is. 
 That said, if you're always wanted to build one and the funds / time permit, rock on.

[dave500]

not hard to remove rings,always good to clean the grooves and backs of the rings,be sure they can rotate,check gaps and good to go,so long as your not ham fisted its not real fiddly.

[Papa-wheelie]

Thanks everyone for the tips so far.  I'm one of those guys that [at times], has a little more ambition than ability .  I've never done a top end before and had no intention of doing one now.  The bike ran fine, minus the fact that it was leaking oil all over the place.  I thought I could remove a few covers,....slap on a new gasket, ....button it up and be done with the leak.  However, now I find myself all the way down to the bottom gasket.  In addition, it seems that I now need to learn a bunch of stuff [camshaft timing, tension setting etc] that I don't know how to do; or even what needs to be done.

I just purchased a Clymer manual M336 online and am eagerly awaiting its arrival.  I'm going to go to Harbor Freight and purchase a 3/8 torque wrench [5-80 ft lbs] for $9.99 w/ super-coupon! as well as a blow gun attachment for my compressor to blow out the sandy grit that is currently in the bolt holes, [along with some pipe cleaners and brake cleaner spray].   Hopefully the manual is clear enough and easy enough to understand what to do and how to do it.

I'm still at a loss as to which gasket kit to use.  Expensive Honda individuals, medium priced Athena brand complete kit [$84.00], or the $52.00 complete kit from the brand NE.  I'd rather go with the less expensive brand if they actually work out okay but will skip it if it's a guaranteed to leak.  Any advice on the gaskets? or any special tools I'll need to get this bike back together?

Thanks again for your replies.

[dave500]

ok its all apart so lets also de carbon the head/valves and relap the seats?your wise to replace the valve stem seals this far into it,youll need a valve spring compressor though,you can buy cheap ones that work fine.

[Bodi]

I have never had trouble with Athena gaskets.