Actually Weisco doesn't sell a 78.5mm piston, the smallest is 80mm.
Thought stock was 80mm.....I stand corrected.....Try these if your piston is still good....
http://cgi.ebay.com/ebaymotors/NOS-Honda-Piston-Ring-STD-85-FL350-Odysey-13011-VM0-681-_W0QQcmdZViewItemQQhashZitem43a3818472QQitemZ290505983090QQptZMotorcyclesQ5fPartsQ5fAccessories
If not,it may be well worth the money to buy a 80mm piston and have it bored opposed to paying for a stock piston if you can even find one....
Thanks Hoodlum - I may be over thinking this but I'm thinking that if I go back to an 80mm bore then I should consider a water cooled head - after all that's why Honda went from 80 down to 78.5. I assume they did is to increase the thickness and strength of the exhaust port divider.
A water cooled head might be a good mod anyways![/quote]
WC head will not cool the exhaust bridge....When it is bored,the bridge needs to be relieved a couple of thousands,and holes need to be drilled in the piston to allow cooling of the bridge...There are instructions included with the piston for doing this....They dropped to 78.5mm to give more metal and better heat displacement,but there aren't very many running around now with that size bore....
Just make sure you leave enough piston/cylinder clearance and you should be fine....DO NOT go by what is on the box or it will sieze....Leave a minimum of .005" clearance.....I actually ran one a couple of years with .007 clearance without issues....Not condoning it,just saying what I have experienced...I have also heard of people running as much as .009",but I have never done it..It had a little slap until it warmed up,but that was all....If you are jetting for optimal performance,then leave more clearance....If you are planning to run it on the rich side,.005" should be plenty....Make sure also that the ports are chamfered correctly,or that exhaust bridge will snag a ring.....
Hoodlum[/quote]
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Thanks for the help, I'll post on the board once it's running.
Hugger