Got me stuffed--& i've been stuffed lots [in my dreams]. Anyway, looking on 'FleaBay' & put in yamaha dt2mx jug just to see what came up--just doodling, & there's a Dt250 cylinder with a water pipe atatched above the exhaust port where say a decom valve would fit on a 400 but can just read 246? on the cylinder so assume it is 250. See what ya think!!. auction number is 201031421868 headed "Yamaha DT250 79 Cylinder Jug". Maybe i'm just having a bad 'thinking day'--Cheers.