[BlackdogADV]

I’m going from a stock 130/70-18 rear tire to a 150/70-18.  Do I need a new tube?

[Hoiho]

When I ran tubes; I changed them every tyre change. Haven’t run them for a couple of years now.. 

[Streetliight]

I’m going from a stock 130/70-18 rear tire to a 150/70-18.  Do I need a new tube?

The answer is yes, regardless of your tire size change imo. If you're changing the tires, you may as well do new tubes too, for peace of mind.

In the cycling/mountain biking world, I'd then rotate the old serviceable tube into my backpack as a spare tube in case I had a puncture, but unless you're touring on your motorcycle with a robust set of tools, that seems rather useless to me.