Piston 80.6 mm

 
Why 80.6mm? Aftermarket pistons usually come in 0.5mm increments, sometimes 0.25mm but never seen them for Laverda. If you have knackered 80.5 pistons/bores, standard practice would be to get a set of 81mm pistons and bore/hone to suit.
 
OK, never seen that. Every day is a school day! :) Are you trying to match a piston you already have or need a set? And are you talking 750 or 1000? They have a different deck height among other things.
 
Asso and Mondial in 80.00, 80.40 and 80.60 mm IIRC, never seen 80.20
Aftermarket in 0.5mm increments, and I'd do what Steve suggests, go to 81mm and be done.
 
To all…thanks for your help.

I have the new piston rings and some other parts from OCT and the gaskets from JLO.

My mechanic says that the old pistons are good and can be used again.

Now we are going to take apart the zylinder head to change the bearings of the camshaft and take out the valves.

Because two valves are leaking a little bit (test with gasoline).

By the new piston rings I didnt see any marks how to build them on the piston (there are no marks for up or down side). Is there something special that I have to consider when I will put the new piston rings on the piston?

KR, Mitja
 
First ( upper ) and 2nd are the same
( compression ring )
3rd is the "thicker" Ring ( oil scraper ring ).

Rainer
 

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Make sure that the new pistons rings are properly gapped according to the manual and I think the rings need to be inserted w the correct side facing up, but others can verify this. Also check that the ring grooves on the old pistons are within spec to the manual
 
Top ring is chrome, either side up. Second ring is cast and can’t remember ( but thought they had a stepped recess (which faces down). Oil rings either way. If we’re talking Laverda original. Yes, from my memory 80.0, 80.4, 80.6.
Agree with Ted, check side clearance of the rings. Top groove often has too much side gap (not talking about ring end gap) on well-used engines.
 
OK. So the 1st and the 3rd are either up or down. What is the right direction for the 2nd piston ring? Photo1 or Photo2?
 

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