Re: 1992 Force 120hp
Being the top, #1 overheats first and gets the hottest. It most likely galled the piston, wiping aluminum into the ring lands and onto the cylinder wall. This is the double whammy in that the rings are cold welded into the grooves and do not seal and the aluminum wiped onto the cylinder wall also prevents sealing.
The cure is to replace the piston.
Remove the head and look at the cylinder. Feel for aluminum wiped onto it and feel for scoring. If it is heavily scored you must disassemble the engine and overbore. If it is very lightly scored or only has aluminum wipe-off, you can use a razor to scrape off the excess aluminum, then hone the cylinder (after removing the piston)
To remove the piston without disassembling the entire engine, remove the carb and manifold with the reed Vee blocks. Remove the head. Using a 1/4 inch drive 12 point 1/4 inch socket, remove the connecting rod big end bolts. being careful not to lose the rollers, push out the piston/rod assembly from the block. If you are lucky, the 92 will have rollers permanently mounted in the cages and will be easier to retrieve. If loose, be sure you account for all 16 of them.
Install the rod on a new piston and reassemble into the block. It takes time and is semi-difficult but can be done. Look for other posts about how to reassemble.
