SmokeyMcBong

Hi There I was told you may be able to help
My name is Dave Giles & I live in Johannesburg, South Africa,
I have recently aquired a couple of 2003 Traxter Max XL's which I am busy cleaning up, I have done as much research as I can re the tyre sizes, but cannot get a definative answer.
The bikes I have, have the original 26's on the rear & 25's on the front, I would like to put 25's all round, will that work ?.
I am also lead to believe that these units have a viscous driven front diff, so that should take up any wind up in the transmission, is that correct
There is a slight "drone" I can hear at about 5mph in second gear (it goes away as I accelerate) , I have taken it to a few "experts" & they assure me it is nothing to worry about, it is the viscous drive ??, any thoughts ?
Your comments & guidance will be appreciated
Regards
Dave