Just bought a 2002 Yamaha Blaster last weekend And I think the thing has a piston slap.

Someone said that it could be the exhaust not sealed which mine isnt because there is no gasket on it at all!!

but I stuck my hand in the exhaust port and pushed on the piston and it had some play in it.


If it does need a new piston and rings, what should I do hone it out to the next size or put a sleeve in it?

The only right way to know is to tear down the top end, measure the piston, ring gap and bore and compare the numbers to factory specs and replace as needed.
If your Blaster has a lot of time on it and you haven't replace the top end parts in a while, say about 60-75 hours, then it's overdue.
The secret to a long lasting top end is quality oil and clean air filters!