Topic: cb350f rings in oil pan

[monsterbuck2006]

So after cleaning the oil pan I found part of a ring.  This is a $100 dollar bike that I am in the process of restoring.  My biggest question is since I now have to do a top end at the minimum can I put std 400f pistons in this with having to do a lot of boring.  Just rehoning the cyclinders and new 400f pistons on the 350f rods and new wrist pins?

[Powderman]

No, you can't hone 4mm. Your cylinders need to be bored to fit a 400 piston. You will be at the limit for overbore on the 350 cylinder. You can fit 400 sleeves to the 350 cylinder head and then bore for a 466 kit.
I imagine that once you pull the top end you may find the cylinder wall beyond honing if that ring  floated out of its bore more than few RPM.

[seanbarney41]

Are you sure what you found is part of a piston ring?...much more likely to be part of a transmission gear/bearing retainer

[monsterbuck2006]

I am not 100% that it is a piston ring.  Before I disassembled the bike to a pile of parts to clean and paint, I was able to ensure it does run by rebuilding the carbs, new plugs, wire caps. etc.... There wasn't any strange noises that I noticed.  No real noticeable white or blue smoke from the exhaust.  And it did have over 100# compression on all cylinders.  The piece may very well may be from some other part of the engine...the trans area.   I guess now I have to decide whether or not to leave alone and just build it and hope form the best.  I am open to all advice on this one.  Just to let you know I m not new to building or restoring just this is the first Honda cb.  Thanks for all the help in advance.

[MoMo]

can you post up a good close-up of the piece?  Might help with feedback...Larry

[scottly]

The usual cause of broken parts of piston rings in the pan is they fell in there when the PO re-ringed the motor. If the compression is good, run it. Don't fix it if it ain't broke.