Right you want to tone your abs and lose a bit of weight?? Ok then
1. keep riding but use lower gear and increase cadence, Uses more aerobic energy- carbos stored in your muscle at first, but then when thats depleted the energy system swaps and draws the fat out and convets it into carbos for use by the muscles, hence burning fat!!
2. increase the distance your riding as well but keep the revs up and don't go into big(heavy) gears
3. decrease the intake of Kcals per day to just below the amount your using, this will make the body utilise the fat as energy quicker, cause that fat is the bodys reserve energy store!!
4. do situps, crunches to tone the abs or another good one expecialy if you sit at a desk for hours a day or dont have time/motivation for lots of situps is to just tense your abs for 5 seconds then relax for 5 and repet (as many times as you need to) so easy to do at the desk!!

I hope this helps