Get a complete gasket kit, and replace everything you encounter in the rebuild.
Base gasket (you'll never have another chance hopefully), all the o-rings, everything. Exhaust gaskets etc. etc. etc.
Are you doing the tear-down/reassembly yourself? Do you have all the Service and Parts manuals?
What are the condition of your carb intake rubber boots? They're cheap to replace new and worth doing if they're hard - prevent any intake leaks.
Obviously replace your oil filter when you drain / refill the oil (assuming you're doing that as a part of this. You might want to replace the oil pan gasket while your hands are dirty and your wrenches are out (and you should have the gasket in the kit).
Did you buy the 605cc kit off eBay? From
www.classiccycleparts.com ? Do you know who manufactured the pistons etc? Take some pics as you go and let see them.
I'd be curious to see pics of the new piston rings. I bought the 555cc kit - being installed as I type this. The oil-ring in my kit was a one-peice unit, while the original Honda rings were a 3-peice design. My kit was made by ART - embossed on the inside of the pistons.
Are you rebuilding the carbs while you're doing this? What is the condition of them?
I don't know anything about valves, other than you need new valve seals (again, in the gasket kit).
Oh, and new spark plugs unless yours are brand new.
Basically, I'm suggesting you have as fresh a start as possible after the rebuild, especially when you're increasing displacement. You will probably need new jets in your carbs too... Don't forget you'll need to break-in the engine as if it were new (it will be).
