charging fault driving me mad, and broke

[banditv]

after about 2 weeks of commuting, the batt on the 250 dosnt have the guts to start the bike unless i pull the headlight fuse.
this seems to give it that wee  bitt more voltage to light the fires.
at idle, its charging at just under 14 volts, give it a few revs, and it drops off to bout 12.8v
at 10000rpm its charging at close to 14v again.
i've taken the stator off and checked it, and its not shorted to ground and has continuity between phases.
have just put a new reg/rect in and eliminated a few plugs by soldering the connections.
the battery is brand new.
have tried giving an extra earth between motor and batt and reg/rect and batt with the tin tops jumper leads with no change.
i love this bike to death, but am scared to go for a ride of more than 160km because of this prob.
any ideas?
help would be awesome
cheers
banditv "lyndon"

[Chris H]

Do you have a manual? and is the new reg/rec second hand or brand new? If the bike is giving 14V and then dropping to 12V if reved it would indicate a bad reg/rec, it should hold 14 to 15 V at 4000rpm.

[banditv]

its a brand new reg/rect.
about all i have left to try is getting rid of the plug for the reg/rect completely

[Chris H]

I had 4 reg/recs go in three days. If it does'nt give over 14 V across the battery at 4000rpm then reg/rec would be bad.
It may be worth wiring it straight to the battery via a fuse, iv posted a link to the SV guys reg/rec mod, they use the same reg/rec as the B4 and it shows a wiring diagram for direct wiring. I ended up getting a CBR6 F008 reg/rec as the stock one keep going packing in.
http://eviltwinsbk.com/forumz/index.php?topic=276.0

[stormi]

http://forums.banditalley.net/index.php?action=tpmod;dl=item55
Go through that flowchart.  It should point you in the right direction.  It's nailed it on the head a number of times for me, saved me literally thousands too.

[banditv]

my boss, who has 30 years experience as an auto electrian tells me that motorbike charging systems are arseholes at the best of times.
i have to check the AC voltage from the stator, which should be half of the charge voltage and amperage.
and if that is fine, its a matter of elemenating poor connections

[canyonbreeze]

The stator AC voltage should be higher than the charging voltage, not half.  Could be up to 70 V on the 400 per the service manual.

[banditv]

yeah, i got that backwards, batt voltage should be half of stator voltage depending on current

[canyonbreeze]

Not half, battery voltages should never go above 15~15.5 V while charging.  If it goes above that the regulator isn't working.  Half of 70V would fry your battery, pop your light bulbs, cause nuclear reactions in your igniter, etc.

[banditv]

the stator output voltage can get that high, but thats what the zener diodes in the reg side are for. they only allow what ever voltage they are set at to flow through them. if the zeners are subjected to an abnormally high input voltage, they can get damaged and that is where the high batt voltage comes from.

[canyonbreeze]

Well if ya wanna get technical...  The rectifier/regulator first rectifies the 3 stator inputs into pulsed DC.  This level is filtered and compared against a voltage reference.  The reference may contain a zener but not necessarily.  If the level is too high it switches in SCR's on the 3 voltage lines that shunt to ground.  On newer bikes MOSFET's are used which are much more efficient.  The voltage should never be half the stator voltage if the stator is over ~30V.  If it is then one or more of the SCR's is blown.  They are cheap but the circuits are embedded in epoxy so difficult to change one part. 

[banditv]

i measured the ac voltage at the 3 plugs that come from the stator last night and found extremely low voltage, i.e 8 volts but also noticed that the crimp connections at those leads didnt look very nice, so is possible there is high resistance under load.
will take the bike to work tomorrow and solder all connections and run a new batt feed from the reg/rect to the batt as well as a new earth and see what happens.

[stormi]

banditv,
How are you making out with this? 

Did you ever go through the charging fault flowchart I linked to above?  I've had really good successes with it multiple times.

[banditv]

went and talked to the suzuki head mechanic in town, and found out that i'm measuring the ac voltage wrong.
am going to take the bike to work tomorrow and recheck it, but the mechanic seems to think its going to be a stator problem.
hope its not, as this bike  that i bought for bout 1600 USD has turned into a 3000USD bike.
tried the flow chart, but to no avail.

[stormi]

Wow,.. that's really weird.  I've never seen that flowchart fail before. 

I'm sure it happens, but where did it fail?  Maybe that'll give us a touch off point.  We'll know what we don't have to troubleshoot and what we still do.

How were you measuring the AC Voltage?