Odd Sprocket sizes ???

[bonnetboy]

Thats realy odd sizing,
small sprockets wear chains quicker and your bike will be revving fairly hi at cruise
but if you put it to std now with the diameter differences your going to be up for a chain too , 16 /38 may fit with your current chain and put your gearing close to normal , and 17/38 may even get close to your speedo being accurate ...

It doesnt seem overy high reving but then again ive never ridden another one so not sure what the normal revs would be. But i can tell you my speedo is out a fair bit.
Well i wont be able to afford new sprockets & chain for a while now so will have to make do with the way it is.
Any idea why the previous owner would want to change to thses sizes?