Motorcycle Repair: Charging system problem on Honda CBR900RR, honda cbr900rr fireblade, battery cells

Question
1996 Honda CBR900RR Fireblade.
Charging system does not charge battery below 1300 RPM.  AT 5000 RPM, voltage is 14.2 and during day riding there is no problem.  When I have to use the lights I have to increase the idle speed so that the battery is not discharging during tick over.  A mechanic suggested one of the field coils could be damaged.  The engine casing at the end of the alternator housing has a small bit of damage from a previous spill but it's hard to know if this is the cause.  Another sugestion I was given was that I'm not riding the bike fast enough !  Thanks for your help Mark.

Answer
Hi Malcolm,

Life begins at 140!

Charging systems begin charging their batteries at about 13.5 volts and are regulated up to about 18 volts, typically. I think you need to test the battery cells for specific gravity. The battery may have a defective cell or two.

The altenator should feed the positive side beginning around about 3k rpm. Not much charging going on below 3k.

Won't you send me your email addy so I can send you test info files. A few easy tests may make you right, pal. Send to: mshively1@woh.rr.com

You in the UK?

Respectfully,
Mark Shively
www.fop104.com