It is not a common practice to rent out motorcycles or scooters to foreigners in Siem Reap, alas! If you want to have your own transport, the only option is **bicycles** which are offered at around USD2 per day. Be realistic, though: it is about 7 km from Siem Reap to the ruins plus the same distance back and than add no less than 10 km if you wish to do the Small Circuit. And yes, it may become scorching hot in Angkor.
If you prefer motor transport, than opt for a motorbike taxi, a tuk-tuk or a normal taxi.