I saw several motorbike users during my own tour of this vast site, so I don't think entry is any different for motorbikes than it is for any other form of transport. Certainly you will really benefit from a motorbike because some of the roads my tuktuk went down were really narrow, barely wide enough for us, while temple areas in other parts often had rough area pull-offs impossible for even a tuktuk to negotiate which forced us to park on the edge of the road. With a motorbike you will find it a lot easier. Unless you are taking a guide as a pillion passenger then you need to keep a close eye out for information boards at the front of many temple sites which will at least give you a bit of an idea what you are looking at. Most -- but not all -- have a translation in English but, since my English guide spoke and read Thai, this was not a problem for me. Just make sure you have enough petrol in your tank when you set out because we covered a lot of miles exploring around and I didn't see a single petrol pump anywhere until we got back much closer to the city itself. Hope this helps.

From town to Wiang Kum Kam: most tuktuks quoted 600baht (Dec2016), but we managed to get it lowered. Once you reach the visitor centre, you only have the option of taking horse carriage or the open-air vehicle (good for 10pax). Horse carriage is comfortable enough for 2, maybe fits up to 3 only. It's quite small. No advance booking required for both.

You can visit all the sites easily from a van. We took a horse and cart just for the fun of it and the driver had written information about the various sites. Two hours is plenty of time.

Not sure

I agree with the previous comments. A Taxi is the go. More comfortable and cost wise about the same. However I do disagree that Tuk Tuk's are more dangerous than Taxi's. Having been to Thailand 38 times I have survived Tuk Tuk's everywhere in my travels though out Thailand. It's part of the fun of going to Thailand. Do try going to Masae Elephant show and the Elephant trek over the mountain to the Long Neck Tribe. Fairly close to that is the Tiger Kingdom. Both done in the 1 day as they are close to each other. Another great sight is the hill side Temple Doi Suthep. Magical.