compatibility of two different tires

yes.

your speedometer will read just slightly off, but you will be fine...

From Tire World

another cool site with a diameter calculator built into it...

http://www.buicks.net/shop/reference/tires.html

the 195/70 tire has a diameter of 24.8 inches

the 205/75 is 26.1 inches. it is a skinnier, taller tire.

this should not be enough to give a significant change in handling on that chassis, but a careful first drive is always a good bet...

Tire size depend on whether or not they fit the rim of your bike. Before you start using your winter tires did you considered choosing the same brand of tires? There are a number of motorcycle tire brand that can help riders maintain control in variety of terrains types such as Pirelli motorcycle tires.

If no aftermarket mods have been performed on your rim to tire setup already, it should be fine.

Assuming you have four and not two. Also assuming you do not bottom out on the arches already.

You may want to drop the PSI by a couple of single digits in winter.. It provides stability. (varies based on normal running pressure).

Hello Friends,

Tire sizes express the tire’s various measurements in a standardized format written on the side of the tire, also called the sidewall. The three measurements included in all tire sizes are section width, aspect ratio, and diameter. Depending on their intended use, some tire sizes also include information such as speed rating.
Tire sizes are expressed in the format WWW/AAXDD. WWW is the tire’s section width, measured in millimeters. AA is the aspect ratio or profile of the tire, which expresses the tire’s height as a percentage of its width. X is a letter indicating the tire’s internal construction. DD is the diameter in inches of the wheel that the tire is intended to be mounted on. An example of a tire size written in this format is 225/50R16.
This particular tire has a section width of 225 millimeters (8.86 inches). Section width is measured from the widest point of the outer sidewall - the side with the tire sizes and brand name that faces out from the vehicle - to the widest point of the inner sidewall when the tire is mounted on a specified width wheel. Narrower tires have lower section width numbers.

Thanks and Regards,
Umang Kumar