Fitting YZ piston to 04 RM 250

I don't think that the stock YZ250 piston is a single ring. I'm not sure about the height difference but I would be happy to measure mine for you if you'd like.

the piston you have been talking about is the YZ250 Wiseco GP race piston- yes its a single ring, and i think its a bit taller.

this will alter the port timing similar to milling the cylinder base- ie it lowers the ports to make for more bottom end at the trade of top end. It will also increase the compression, so you have to consider fuel etc.

if you want that type of powerband, i would look at the regular Wiseco 2 ring piston and run the high comp (thinner) base gasket from cometic.

Me, i will be looking at running a thicker gasket to try and get some more topend!!!!

I have the single ring YZ pistion in my 03 and I did loose some top end but it gained bottom It also knocks a little when i run pump gas