Mike is right but there's more to it.

A 60 watt bulb draws 5 amps at 12 volts, a 100 watt bulb draws just over 8 amps. So with two uprated bulbs you're going to draw an extra 6 amps. This may well blow the standard fuse. However, just putting a bigger fuse in to stop it blowing, does not change the fact that the existing switches and wiring are now handling those extra 6 amps. So yes, you may well be compromising things. Sparking at switches and relays, plus wiring running hot are possibilities.

Plus, more heat in the headlamp housings can start to melt plastic fittings!

Just as a final thought, is it legal where you are?

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Cheers, Neil