There are a few things that have power to them all the time (IGN SW,FuseBox,R/R,Solenoid).
There are many things connected to the harness that have power applied when the IGN is on(including the Horn).
So theoretically anything with power applied (including the harness itself ) could develop a short to ground.
Recalling from my memory banks, the historical top list of causes of shorts are:
- Bare or broken wires
- Shorting mounting bolts (at the coil)
- R/R's
- Melted fuse boxes
- Melted connectors
- On rare occasion Internally Shorted Horn.
I don't recall shorting horns to be reported much as the cause of blown fuses. Could happen and it could be vibration induced as well. Those are all guesses, the only thing we know for sure is the Fuse Blows. The OP is in the whitewater of statistical guessing to minimize his time to repair. What is the best approach?
As I inferred, a statistical approach weighted by "time to diagnose" can produce an optimal solution. Given that everything you try costs time (if not money) what trials is the most likely to produce a positive result where you have diagnosed the problem in the shortest time. Anything could be vibration sensitive, and so you could go through a process of elimination removing things you don't need and ridding around till the fuse blows or you confirm that it does not blow.
#1 Looking for Bare or broken wires is an alternative way to look for something that might be shorting after riding and there is movement. Shorting wires is also high on the list of known faults. I would do this first as at it costs little, can be done fairly quickly after removing the gas tank and should provide the opportunity for spraying some contact cleaner for maintenance. So time wasted is actually minimum if you attribute the time to needed maintenance. We know now that this did not yield anything obvious.
What next? What is most likely with the minimum time repair at lowest cost? It is certainly low cost to revert back to this trial and error vibration induced short search. It is however not particularly economical in terms of time. In addition the only items that historically tend to short out are the R/R's and Coils bolts. So while looking for vibration induced problems costs little (except gas to drive around the block) it is expensive in terms of time and low probability in terms of historical record. What to do next?
#2, My conclusion and therefore my recommendation to jump right the replacement of the R/R despite what appears to be reasonable (if only functional ) charging is A.) The high likelihood of the R/R being the problem (given no other visible shorts are indicated) and the high probability of failure in such devices. In addition, biased as I am, I would consider the replacement of a OLD Style split R and R to a new SH775 or at least a Honda 6 wire unit as a "mandatory" maintenance task, and so it is no cost to diagnosis. It is highly recommended before the stator gets any more stress and the OP can save what Remaining Useful Life he has in it. Will that fix the problem? Probably? Possibly? We dont know. But it is likely that it will and at nearly zero time lost given we consider it necessary maintenance.
Alternatively, it could have been the OP has more time than money and he would choose to chase down this vibration induced shorting. Consider the case that our high likelihood candidate (the R/R) is the culprit and we choose to not change it but rather test everything else. How long do we and how many items do we test till we conclude by a process of elimination that it is in fact the R/R that is the remaining source of the short because we can't find it any other place. Even the cheapest GSR tightwads will have to acquiesce at some point and swap out the R and R. Would it not be better to just change it and get the maintenance done (R and R upgrade) and probably solve the problem the quickest?
Now if after changing out the R/R and cleaning up the grounds and charging connections in the process we still have shorts blowing the Main, then that would be a real puzzler? And then you would have to start eliminating things, but as mentioned above, that would be a lengthy process. At that point I would be tempted to go to a multi fuse position fuse box to help isolate circuits.
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