I have a 1985 fl350r. Not sure exactly what size the piston is. It has the x stamped at the end of vin number. Which from what I've heard means it was recalled. So how do I tell if this is the 78mm or 8omm head and what do they mean when they say the fins are turned. Thanks for any help

If the X is stamped after the vin then it should have the recall head with the fins in the picture below. The fins turn out at the front to help redirect more air over the head. The original head had fins that went in a straight line front to back. You can measure the bore in the cylinder with a micrometer and that will tell you the current size. The pistons sometimes have numbers on the dome from Honda or wiseco and those will also refer to a size. See second picture. Post pictures of what you have and it will be easier to tell/explain.

Thanks for the info. I do have the turned fins. I checked the bore and it is the 80mm piston. Thinking about taking it to 81mm. If I do should I use a cool head or will running a fan blowing directly on the motor (( Internal Combustion Engine ? )) work. I have seen one with the fan setup a was told it worked fine.

Have the place that will bore the cylinder measure it for you. If you can get away with and find an 80.50 then I would do that. No sense in going to 81 and skipping a bore size. Look up Oddy-cool on eBay that is a kit, Others have probably made their own though. Water cooling would be best, check some of the Facebook ody pages (used ones pop up) or contact methodical fabricator as he makes water cooled parts for the odyssey.

Ok thanks for the info. I will check them out