Hello guys! 
Today I realized that my motor still uses a 81 mm piston size which means last possible size. Correct? Any ideas when I‘m going to change piston? Is there the possibility for a similar piston (maybe from the 400 model)?
Thx!
Gerry

This image is hidden for guests.
Please log in or register to see it.

 

If there's enough "meat" left in the cylinder, then Wiseco might make one. Alternatively, look out for a replacement cylinder on fleabay etc (make sure that sellers aren't listing RT1/2/3 cylinders as ones for DT360! ).

I would say yes, there is enough meat….

I use a 2X5 kit which is 82mm in two of my 360's. It's from a yz400 1979 "only" 'one year'. Don't go with earlier 400 85mm kit or the fins will fall off haha. For safety you need about 5mm off the skirt base although I forgot on one of mine. If you fit the piston on the rod & go to the bottom with no cylinder you can check how much forward & aft clearance there is to rock the piston. Anyway, put it side by side with your old one will show how much difference. Good apart from that. Big cut away piston not two holes.

Wiseco makes a few in that size, the closest fit overall is the 639M08150. You will need to make a spacer 2.5mm thick and run a base gasket on each side of it to raise the cylinder and correct the deck height. These are available up to 82mm so if you go 81.5 for now you can save that last bore for another time.

I ordered a plate of aluminum on ebay for about ten bucks, at that thickness it is easy to work with. Hack saw, drill and file it into shape.