Its a very precise thing to drill out jets as the orifice must be smooth. You may be able to do it with a wire-size bit set and a pin vise. A dial or digital caliper could come in handy. IIRC, jets are calibrated in 'wire-gauge' already, so the wire-gauge bits are a natural for this job. You can use the shank end of the bits to determine the existing size and simply go up one size to start with. Try that and see how it runs. You should actually mow with it for at least ten minutes to get a good assessment of the results. Obviously you have to remove the jets to do this so you don't get any debris in the carb. Very carefully remove any burrs on both ends of the orifice before re-installing.
The idle and hi-speed RPM may increase when the mixture is enriched. You adjust this with the knurled disc at the base of the air vane on top of the carb. This is the governor spring pre-set and it moves both lo-speed and hi-speed limits at the same time, so you will increase or decrease both ends of the speed range at the same time. Four clicks on this adjustment (clockwise for faster) is pretty much the max.

So do the jets you buy have to be drilled out too? I took the carb apart and cleaned but still surging, thought I would just drill out the current jets rather than buying the others if they have to be drilled out as well.

If you search the forum, you can find links like this-

http://forums2.gardenweb.com/forums/load/lmower/msg0910272311499.html

Replace the $5.00 pilot jet with either a

Briggs & Stratton #801308

Mikuni #N101.043

Cures most surging problems and no mess up if you drill the factory one out to large or untrue (oval).

I drilled mine with no problem. IF you have access to the drills, why not try drilling, IF results are not good, then you can buy new ones instead of giving up first.

Walt Conner