On_the_busas
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| posted on 17/4/14 at 07:33 AM |
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Megabusa low voltage
Hi,
First of all apologies for this being my first post and not introducing myself properly but i have been busy trying to sort this annoying problem out
since buying the car!
Picked up my Megabusa about a month ago, stunning looking car with the right spec, exactly what I wanted! Unfortunately now having issues with it
since driving it back from buying it. I don't want to drag the story out too much but basically all was well with test drive no issues
whatsoever, picked the car up two weeks later.
Driving it back had to stop for fuel around 35 miles into the journey, went to restart after filling up and......bloody flat battery! No problem, got
my convoy who were following to bump start me but then struggled to keep it running, very rough and misfiring, almost pulled over on the side of the
motorway to stop as I thought the engine was shot. Turns out around +6k rpm runs sweet with no problem, so got it the rest of the 100 miles or so back
home up the motorway (although some funny things happening with gear shift indicator and wasn't sure the rev counter was reading correct
either).
Anyway, got the car home, decided to get a new battery so managed to get one fitted but having issues with low voltage across the battery around
12.6-13.0v max when running at idle and revving 5k rpm. Had a scratch round the internet and decided I will change the reg/rectifier unit, now the car
doesn't even want to start with the new unit on, misfiring and then eventually battery goes flat after trying several times!
Checked my earths, there does not appear to be anything untoward, all clean and tight, connectors all good to (no melting/fust)
Checked stator output in all 3 phases and over 80v at higher revs.
With the old reg/rec fitted it runs but eventually when voltage drops low the misfiring commences. New reg/rec unit seemed ok when engine was warm but
certainly wont cold start on it unless I disconnect it.
So now i'm in the situation that its looking as though the new reg/rec unit could be faulty or the stator is grounding and/or knackered.
Has anyone on here had any experience with this issue and if possible could you suggest a route to go down? It's doing my head in but I think
deep down I know the engine will probably have to come out to change the stator.
Apart from that the car looks nice sat in the garage with these sunny days passing by!
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Wadders
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| posted on 17/4/14 at 08:34 AM |
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Sounds more like the Reg/Rec is faulty, (although every one i have had go wrong gives over voltage not under.)
or you have a bad connection. Check the charge wire which will probably be connected
to the start relay, usually through a 30amp fuse, they sometimes corrode. i would take the charge wire ( through a fuse ) direct to
the battery + terminal, this ensures the connection is good and you can rule it out.
Then use a multimeter to see what voltage you are getting at battery + with engine running, should be around 14v DC.
You can check the stator output between any of the three phases, you should get around 50-70v AC, also check continuity between
each phase and earth, it should be zero.
Was the new reg/rec a Suzuki one or a pattern part ? might be worth trying another one, sometimes new stuff can be faulty
You can pick new pattern ones up for £20 or so.
Al.
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On_the_busas
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| posted on 17/4/14 at 09:01 AM |
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Hi Al,
Thanks for the info, certainly gives me something to go on, it's just finding the time to look at it!
Didn't think about the charge wire and start relay. Stator output looks good on all 3 phases being the same at around 40-80+v depending on revs,
didn't find anything with my continuity checks but will run through again.
The new reg unit I got was a pattern part but not a mega cheap one, like you say it could well be faulty but for the sake of a 2 min job could be
worth trying another.
I will keep it posted on here.
Cheers
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theprisioner
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| posted on 17/4/14 at 06:19 PM |
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The original 12.6-13.0v sounds normal to me anything above 12.4V is good news. Try switching your lights on you will find only a charge at 30mph.
This is because a Bike only has one headlamp and one tail lamp. I think you should put the original regulator back in and make some more measurements.
http://sylvabuild.blogspot.com/
http://austin7special.blogspot.co.uk/
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On_the_busas
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| posted on 17/4/14 at 07:41 PM |
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My concern is that something is clearly wrong somewhere down the line as I wouldn't be getting the rough running and misfiring if battery
running voltage was ok, although made little difference when running with headlights on the other day (in garage). This is also added to by the fact
that with a fully trickle charged battery and rectifier unplugged it runs perfectly, as soon as the old and new rectifier is connected back up the
engine does not run cleanly. Also it will not start on the new rectifier until I unplug it. It's very strange and I'm no auto electrician!
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theprisioner
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| posted on 17/4/14 at 08:01 PM |
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I think the problem is in your Bike ECU/Electronics. It sounds like something is not grounded properly.
http://sylvabuild.blogspot.com/
http://austin7special.blogspot.co.uk/
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rick1962uk
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| posted on 17/4/14 at 08:10 PM |
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hi to start off with you need a good battery go for yuassa and make sure its charged fully if you have a dud battery it will send the clocks etc mad
also then try all the earths are good and connectors have good contacts and are good quality
where are you based and what make of reg did you get electrex are very good tourtec are hit and miss
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matt_gsxr
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| posted on 17/4/14 at 09:34 PM |
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Worth checking all the earths are good.
Failing to start indicates (to me) that the signals from the crank sensor are not being seen by the ECU perhaps owing to interference from generator.
Poor earthing could cause this, poor earthing can also cause problems with charging.
All the other faults are consistent with poor charging (low battery yields poor spark and miss-fire, miss-fires result in jumpy RPM, jumpy RPM upsets
the gear indicator).
If you can't deal with it yourself then a motorbike mechanic will sort you in almost no time and get you out in the sunshine.
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On_the_busas
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| posted on 18/4/14 at 12:37 AM |
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Thanks for all the responses, very much appreciated!
I think that I am going to have to go over all the earths again and thoroughly check everything, including changing to a new reg/rec just to try and
rule out two faulty ones! The battery I bought was a brand new Leoch premium gel battery, it was a Yausa that came off it. I think if these checks
don't solve it I will get someone in to come and look at it, already been in contact with a local mobile bike mechanic/electrician, I'm
based in the Notts/Newark area.
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On_the_busas
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| posted on 25/4/14 at 12:07 PM |
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Right, ive managed to go over my earths again and change for another new rectifier. Seems to be sat at around 13.4v-13.6v when running at battery (at
tickover, doesnt seem to move voltage with revs) If I check directly out the back of the rectifier connection its around 14.0v. Need to wait until its
nice before test drive but the misfire has certainly gone now and starting ok. Think I may wire the earth from rectifier to battery directly to rule
out any other bad bits in the wiring. fingers crossed now!
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On_the_busas
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| posted on 25/4/14 at 03:12 PM |
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Managed to get out, just dry enough..... if a little greasy! After 20+ miles, a bit of fuel and 4 starts it's certainly running well with no
misfiring or problems as of yet. Checked battery voltage when back (not running) and measured 12.8v which seems ok for me to fire up again. Will keep
an eye on it but considering fitting a voltmeter in the dash, although I think my new shift-i shift lights should cover that one! ;-)
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