[peteb1951]

If I put a 44 tooth rear sprocket on a 2016 ST to improve acceleration can the stock 520 chain still be used or would I need a new chain with a different pitch?

 

[twinsisin]

If I put a 44 tooth rear sprocket on a 2016 ST to improve acceleration can the stock 520 chain still be used or would I need a new chain with a different pitch?

If you order the correct sprocket with additional teeth it should be the same pitch, but the stock chain might be too short..

 

[CafRacer]

Gearing commander website shows a 44t will move the wheel forward about 10mm with the stock chain, as long as you have room for that adjustment you should be fine, if not you'll need a longer chain.
520, 525 or even 530 chains are all the same pitch, just different widths.