Super Thumper
The stock sprokets are 23/68.
I can tell ya that 24 is the biggest sprocket that will fit on the front and there ain't no extra room. I can also tell ya that a 150/90-15 is the biggest tire that will fit in the stock swing arm (axle completely forward). I've got both on mine and I can tell ya "Ya doin't want to go any taller on the gearing , these added together make about a 19% speedometer error". That is speedometer indicating 60mph / ground speed is really about 72mph. Needless to say I doin't go over the indicated 55mph in a 55mph zone.
I'lll go with one size smaller tire next time!