Hi. I've got some free time, so I decided to build something like your circuit, to see if it'd work. The Colpitts oscillator is the same, but I decided to make some changes:
1. Instead of a fancy UHF transistor, I used a jellybean BC550C in the oscillator. Everything else in the Colpitts is the same.
2. Instead of the comparator, I used a emitter follower buffer (BC550C) and then a switching transistor (2N2369A). At first I used another BC550 as a switcher, but it was too slow from 3MHz on.
The circuit is simple, it took me little more than an hour to build, and it works all right. I attach the schematic, a picture of the circuit (the small mushroom is the 2369A, the other two are the 550's), and the oscilloscope capture of the output for a short circuit, a 30uH axial inductor, and a 1000uH axial inductor.
Perhaps your circuit is failing by some other reason than biasing. And you only need three more or less jellybean bjts to build an equivalent working circuit. The switching transistor is biased quite hard (10mA), because at first I was using a BC550 as the switcher. I think that with a 2369 the biasing can be quite relaxed.