Where do you want to start you ride in Kyrgyzstan: Bishkek or Osh?
In any case, you may want to consider flying to/from Tashkent instead, back in 2005 the road into Fergana Valley was soooo much better from Tashkent than Bishkek. Uzbeks are pretty good with road maintenance, though admittedly for the wrong reasons. It will also give you more choice with flights as Uzbek airlines are actually pretty good and the last time I checked Turkish flew to Tashkent too. Best thing, there may be still a direct Heathrow-Tashkent connection with Uzbek airlines, so no changing in Istanbul which is never fun with a bike... Check it out.
If you want to start riding from Osh, rather than cross Tien-Shan by bike first, flying to Tashkent makes even more sense as a minibus journey to Osh is much shorter, over lower mountain passes, and on better roads than from Tashkent. Should be cheaper too. If you want to ride your bike through Tien Shan, then the Kyrgyz road is far scarier and more demanding but far prettier too, and you may get to ride horses a lot too, so up to you!
BTW this is all I can advise as I was there without a bike and 9 years ago. Do go, it's a stunningly beautiful place!
