The XR650L is the electric start version of the 600R not the 650R.
The 600R and the 650L are both aircooled, steel framed, 80's tech singles. The 650L has a more robust subframe and a few other bits as well as the electric start but essentially the two bikes are first cousins.
The XR650R has virtually nothing in common with either of them (other than the makers name ). It's water cooled with an ally frame and much more powerful than either of the older bikes. As you say, it's kickstart only and I've no idea whether a conversion kit is available. Other's may know but I've not heard of one.
Hope that helps