There are a few options - depends how bu99ered the screw head is? I've had most success with method (1) on this size of screw.

1) Use a hand (hammer) impact driver. Tap the bit in first, to get it seated nicely in the damaged screw head before using the impact driver. Don't whack it the impact driver too hard - one firm tap should be enough to get things going with a bit of luck. (A bit of fine valve grinding/lapping paste can help to get a screw driver/bit to grip better.)

2) Use an EZ-Out. Drill small hole in the centre of the screw, insert EZ-Out and wind in drawing the screw out. Not a ideal method though as its a very small screw and a very small EZ-Out and there is a knack to using them - they can break off themselves and then you've got a piece of hardened steel to drill through using method (3)!

3) If all else fails - Carefully use a bigger drill bit to take the head off the screw, making sure you get the dead centre of the screw, then remove the reservoir cover to expose enough thread to get some grips on.

There are probably many other ways too...

Good luck!

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