Inner Tube Size for 400sm?

[stizo]

Hey, just had a quick question about which tube size I need for the 17" on my SM. I'm putting a 2ct up front (120/70/17) and a regular Pilot Power (150/55/17) rear. I just wanted to make sure I buy the correct tubes before I had the tires mounted. Also, can I reuse the stock tubes or should I just replace them though they're still good? Thanks in advance.

[supertireguy]

4.5x17" inner tube.

[Mondo]

Just reuse the stock ones. I used the same tube from the original 140 tire in a 160 slick and it worked fine. No reason to replace them if they are still good.