I run marathons, ultras etc for 'fun' and cramp is an issue with those events. I've had to try and deal with it as best I can as just packing up in the middle of nowhere isn't really an option. In terms of what brings it on for me the most common reason is overuse - for leg muscles anyway. After that it's dehydration and thirdly it's electrolyte imbalance.

It's not that difficult to get overuse cramp on a motorcycle, especially if you suddenly up your time in the saddle. Long days sat in an awkward posture can create leg strain without you being aware of it. Add in a bit of dehydration and the two together will bring on cramp. Dehydration (a small amount anyway) is something that responds to training. Your body will adapt to it but if you're not used to it - you live in a cold climate and suddenly go somewhere hot - it will have consequences.

I'm not so certain about electrolytes. I've tried all sorts of fixes with this - more/ less sodium, potassium, magnesium etc, just about every commercial fix I can find, and the jury is still out for me. Even professionals I've spoken to give me mixed messages. By default I use dioralyte, mainly because it's cheap and it doesn't seem to make things worse. It works like magic if you're really dehydrated but for cramp, well, it doesn't hurt as long as you don't overdo it.

That's cramp, but as other have said there's other stuff - like nerve pinch pain - that has a different source. It's not that difficult to tell the difference once you've had both but I suppose muscle fatigue could feel a little like cramp at the end of a long ride.