Beeing an aircraft maintainer, I can tell you that nearly 90% of all problems are cause by maintenance "we" do. I'm not saying you messed anything up but I'd start looking where the last maintenance was done. If it were my bike, and I'd just worked on it....I'd start looking there. Like Glider said, could just be a loose ground wire. I would not use a higher amp fuse to try to fix the problem.