What is the kerb weight of Kawasaki Ninja 300?

The recommended tyre size for Kawasaki Ninja 300 is Front:-110/70-R17 Rear:-140/70-R17. Moreover, upsizing the tyres is a possibility but there will be some effects on vehicle performance. If you replace any part with a different spec, you will most probably have to change some other related parts as well. So, if you upsize your tire, there is a chance that it might start brushing the swingarm and that will result in faster wear and tear than the normal rate. In terms of performance, with a wider tire, the performance will also be on the decrease, which can be seen in the fuel economy and the top speed of the bike. Also, the increased contact of the tire with the surface results in increased efforts to handle the bike.

Absolutely... the seat is too low that a 5 feet person is also good.