Motorcycle Repair: system charging problem, fuse box, affected systems

Question
hey chris hows it going? i have a 1983 yamaha virago xv500 that all things considered runs really well. I am having trouble trying to locate a short in my charging system. i know its there cause when i am riding and i hit a bump, the headlight gets really dim.But if i hit another bump or jump down on the seat it picks back up.My problem is that when it is sitting still it charges fine,so it is hard to detect the short.What do you suggest i do?I did replace the fuse box under the seat,but all connections there are good.i have looked for any visable signs of wear on the wiring harness or any kinked wires, but cant see anything wrong.Thank you for your time.

Answer
Hi Ken.
 This is the part where you are going to both kick yourself and prepare to scream in frustration.

First of all, the problem is not in your charging system.  The problem is in one or more of the wires directly under your seat.

More than half of all shorts are completely invisible to visual inspection.  You will need to get a multimeter and the repair manual so that you can test the wires that are for the affected systems that go directly under the seat.  One thing that you need to focus on are the contact points of the seat as it relates to the position of the wires.  Those are the wires to look at first.  Check the connections as well, since you could also have loose or corroded connectors.

Start with that and see what you find.
Good luck.
FALCON