On a cbt you can ride up to a 125 with so much bhp or something. You want a 125 2-stroke to start with, trouble is the prices are getting higher on the old 2 strokes now. Dtr125 are popular, few if my mates have them. All the new ones are 4-stroke and not very exciting. The bike rules are rubbish now. I had my 250 on the road at 17, full licence at 19 lol a full size bike . I go out for the whole day on my bike covering miles. You need to find byways round where you live and make some route up. I'm quite lucky having lots of good areas round me. It's gone down hill in the last 6 years. Nearly all the unpaved byways have changed to restricted byways! But if you get a sm you can have just as much fun on the roads