10w40 is recommended and you used 10w50, right?
This shouldn't be a problem and is largely determined by the environment you ride in and the type of riding you do.
example - Street riding in the arctic might warrant 5w-30 while racing in the Arizona desert might warrant 20w-50.
By using 10w-50 (versus 40) you're still starting a cold engine with oil rated at 10w (W means Winter) viscosity and as things heat up the 50 remains a little more viscous than the 40 - but under most conditions there isn't enough of a difference to cause a problem.
Are you experiencing a problem of some sort or just more generally concerned about the difference between 10w-40 vs. 50?