Could an old, beat fuse box cause finky running?

I was wondering because my headlight went out halfway down the road and it ended up being a blown fuse. I took the turn signal fuse and replaced it and turned around. One thing I have had a problem with is everything dimming at idle and, of course, getting nice and bright at hiigher revs. One thing I tested tonight was the fuses. My 20A is showing 16. I tested a theory and with good, solid connection, the headlight will be just as bright at idle as with higher rpms. So I am wondering, since the igniter has a fuse, would a weak fuse set up cause the bike to run worse? My bike is running good, but it is just a question for future reference.

 

You should dim at idle and get brighter at higher revs because the alternator's output varies with it's rotation speed, aka your rpm. It's 19A, at 5k rpm, IIRC. How much it dims relates to many factors, though.

I can't tell, did you say you bypassed the fuse and you had no apparent variation of brightness in relation to the rpm? If so, you might need a new fusebox. The wires in the system have increased in resistance and might need to be replaced.

I'm not entirely sure what you mean by "my 20 A is showing 16". If you put a known 16A through your 20A fuse and it blew, then the fuse was out of spec on the safe side. If you mean you measured amperage across the fuse contacts, then you should know that if you had measured 20A, you would no longer have a fuse. The fuse is designed to open (blow) at ~20A (ask an electrician for details). You should measure something less than the rating of the fuse across the fuse contacts.

That being said, you are partially correct. A weak fuse (out of spec) would blow at too low of an amperage and your bike would stop. A poor connection, however, could reduce the power to the coil, reducing spark.