Hi there,
I personally haven't done a motorbike trip (I have one in the works) but I have been travelling as a lifestyle for the past two and a half years and I write a blog specifically about travelling long term with diabetes to encourage type 1 diabetics to get out there and do exactly this kind of thing!
So first let me say IT'S POSSIBLE! And a very exciting prospect too. You will just need to plan a number of things in advance for certain. My most risky stint was probably when I was travelling around India for 5 months and in the end, I didn't have a glitch.
So here's my advice...
As for hypo supplies. Definitely stock up on as many packets of glucose tablets as it is possible for you to carry, alongside all your other gear. SAVE THESE for those times/activities when you are out in the middle of the sticks with absolutely no shops or civilization around you. Rest assured other than at these times, there's nowhere I've been in the world yet that doesn't have coca cola being sold somewhere within a ten mile radius. From the foothills of Kilimanjaro to Patagonia in Chile to rural India, there is almost always a little shack, refuge or corner store of some sort that sells coca cola. Therefore it is unlikely that you will often be somewhere where there is nothing for you to buy. And re-stock as you go with other lightweight hypo supplies so cereal bars or whatever local carbohydrate alternative is on offer - you'll discover that as you go.
As for your medication: The NHS is legally allowed to prescribe you up to three months worth of medication at one time, so that will start you off. For the rest of the time you will need to buy your own medication. Costs vary significantly from one country to the next - it really depends where you are going. The USA is extortionate in costs for diabetes medication. Most countries is South American are very reasonable. Here in Brasil it costs me $20-25 for a pot of 50 test strips. I've even been told I'm eligible for free insulin, if I switch brands (which I personally don't want to). As for obtaining it, I simply need to show a copy of my home prescription in order to get it from the chemists. So bringing at least one copy of your home prescription with ALL your medication on it is absolutely necessary. This process of obtaining your medication through showing a copy of your home prescription will be the case for many countries. In other countries you may have to see a doctor first to get a local prescription, in which case, as long as you have declared your medical condition to your travel insurance provider, they should pay for this doctors visit.
Be aware that not all countries/regions may have your brand of insulin. Do your research ahead of time, according to your itinerary and speak to your doctor about alternative insulins you can use, and how to use them, if you can't get hold of your regular brand on insulin.
To be clear, travel insurance companies, even when you have declared your diabetes to them, do NOT pay for your ongoing medication.
Also take at least one copy of a letter from your doctor stating that you have type 1 diabetes and that you need to travel with your medication: insulin, needles and test strips, at all times. This is to save you from any trouble with customs officials, especially when flying.
That's all I have time for for now, but if you have any other questions, please don't hesitate to ask! You can also find lots of other information on my blog.
But I strongly encourage you to do it: I understand your reservations entirely, but, at the end of the day, I feel I won't let anything hold me back from doing what I love. I only have one life, so I'm going to live it my way!
Best of luck!