Did you hear only one sort of loud pop at start up? If so check the heads nuts for being loose
one of my bikes did this kind of made me go what the ????? So I broke out the torque wrench and checked the nuts on the head sure enough they were loose, tightened them up to the torque
I like to use on the 10mm nuts which for me is around 110 inch lbs. and no more pop on start up.
This might be happening on your bike wouldn't hurt to check them might save you a blown head gasket.

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