Hi Scotty, my motorcycle is about 10 years old, and has done around 50000 miles, the manufacturer recommended oil is 10W-50 4T, I was thinking about changing the oil to 20W-50 4T , what do you think?
Stick to what the factory recommends. My '79 Pontiac has tight fitting piston rings and requires heavier oils. Anywhere from 10W-30 to 20W-50, depending on ambient temperatures and the state of internal wear. Yours isn't like that. It was made in 2013.
20W will wear your engine out faster because it was intended for 10W (there's a formula, cold weight is equal to a 10-weight oil, you're intending on putting 20-weight oil, which is more viscous and will take longer to pump).
Be sure to choose an oil that is safe for wet clutches - many of the new car oils have anti-friction additives that will make your clutch slip. My Suzuki manual says, "Use oil with an API (American Petroleum Institute)
classification of SF/SG or SH/SJ, or with a JASO classification of MA" If you don't have an owner's manual handy, you can usually download it from the manufacturer's web site.
Like Scotty, I prefer Castrol - in this case Actevo 4T 10W-40 Synthetic Blend Motorcycle Oil
