So I was looking through the wiseco pro-lite pistons on RMATV... and i noticed... the 2010 YZ 250 Has a 66.4mm piston, and I thought to myself, this is a little bit of an odd size. Yamaha: Bore x Stroke 66.4 x 72.0mm
I jumped back to the 88 YZ which had a almost square bore 68mm.
I then jumped over to my bike a 1996 RM250. Guess what I see? Its piston is ALSO 66.4mm. Suzuki: Bore x Stroke 66.4 x 72.0mm
So that means Yamaha changed their engines and they now have the same bore and stroke (66.4x72mm) as a 96-08 RM250's. Now thats comical
I jumped back to the 88 YZ which had a almost square bore 68mm.
I then jumped over to my bike a 1996 RM250. Guess what I see? Its piston is ALSO 66.4mm. Suzuki: Bore x Stroke 66.4 x 72.0mm
So that means Yamaha changed their engines and they now have the same bore and stroke (66.4x72mm) as a 96-08 RM250's. Now thats comical