I'm not too sure what it is about the Honda CBF250 but they seem to loose their valve clearances really quickly between services. The past few that have come through the shop have all required shims to be replaced to get the valve clearances back within spec. And on the CBF250 they need checking every 12,000k's. The Honda CBF250 that was here today was the worst example that I've seen. In all fairness this bike had not been maintained properly right through it's 21,000 kilometer life and this has played a major factor as to why this bike had issues. The owner was complaining of the bike being hard to start and after a quick chat about the bikes lack of proper maintenance I already had an idea what was wrong. Once the bike was here I went to work on it and it wasn't long before the problem was identified. No valve clearance at all on the exhaust valves. After removing the cams and re-shimming the valves it was put back together. It actually took two attempts to get the valve clearances back into spec and a jump of 10 shim sizes to get the gap correct. A jump of 10 shim sizes is unheard of and its understandable why this one wouldn't start due to the cam holding the exhaust valves open. If you're the owner of a CBF250 and it's due a service I recommend you remind your mechanic that the valves may be in need of some attention. This reminder may be the difference between a bike that goes and a bike that doesn't.