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CBR 600 strange charging issue

Guest carpetpaul

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Hi , this is my first post on this forum and I'm hoping that you can help me with a bit of advise.

I have a '96 CBR600 F-T with 40,000 miles on the clock. It's been well looked after but has been used relatively little in the last couple of years (once every week or 10 days or so for a decent ride)

When it was about 10 years old, the bike developed what looked like a worn out battery, not bad since it had lasted 10 years from new. It was used in this state with the occasional charge and bump start until I got round to changing the battery.

I changed it for a quality replacement similar to the original and continued to use the bike.

It quickly became apparent that the old battery was not at fault and that it was some kind of charging issue.

The regulator and rectifier was suspected, I even had a look with a multimeter and it was not charging well. Sent the bike to the local bike mechanic who had apparently used a dashboard mounted multimeter to monitor the charging as he took the bike for a ride round. Having decided that the R&R was at fault, he replaced it at a cost of £110 to me and gave me the bike back as fixed. (it isn't, but I suppose you'd guessed that)

The battery had been fully charged whilst it was with the mechanic and so it lasted for a few runs. Standing in the garage for 10 days produced an almost dead battery which was finished off when the starter was pressed.

Recharging the battery (tested to good volatge after charge) overnight and then trying to start the bike initially produced good results. It started (with the light on) over 20 presses of the button. However, putting the choke on to allow the started to whizz without firing the engine instantly made the battery flat in about 2 seconds

almost as though the starter is drawing way too much current ?

note : the 20 presses of the button to start the bike normally don't take much battery power (multimeter comfirmed this) as it fires instantly

Riding the bike (previously on the old battery) actually flattened the battery and it could be the case that it wouldn't start even after a long ride

Leaving the bike in the garage for 2 weeks means a flat battery too, and this was never the case when the bike was newer. There's no alarm fitted and the manufacturers quote 600 days standing unused to produce a 100% flat battery and 60 days to still have 75% power remaining.. so it's not that I'm not using the bike enough

any advice on what could be draining the battery whilst in the garage, or possible reasons that the starter motor appears to flatten the battery so quick

please advise on what I could check

charging whilst running is around 15.50 - 15.75 volts at normal 'riding' revs

the charged battery is holding around 14.50 volts

can't measure any drain using the multimter inline of the neg wire

any xpert on electrics, please help !!


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You can usually leave a battery more than two weeks before it loose's it's charge. Have you got an alarm thats draining it too? If not then leaving the bike standing shouldn't drain the battery too much, in which case I'd say the new battery is probably dodgy. Sometimes bike shops have batteries standing for years before they're sold.

To test if the new battery is at fault, charge it and leave it off the bike. Then test it a week or two later.

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