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Breva 750 - Again ! Knowledge much required

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Eibar-Jet200 View Drop Down
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    Posted: 17 Jul 2017 at 16:15
Afternoon all,

I handed my bike into a shop on Saturday as I had got to the end of my technical abilities, Thank you all who advised.

Question now is, Can the Alternator seem to work when not connected?
ie 25v @ tickover and 55 @ 4000rpm but then just fail when connected to the regulator? As that is what is seemingly happening. Yellow wires getting hot.

It is a new regulator I fitted.

So any suggestions? Is it a new alternator and regulator or will I get away with just the alternator?
Best replacement article? It is a Ducati one so is an upgrade better? Or I note that Gutsibits may have a used one.

Please advise as your help greatly appreciated.

Thank you
John

Thanks
John
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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jul 2017 at 22:28
When you connect the alternator yellow wires to the rectifier/regulator they get hot?
 
That should not be and suggests a problem with the rectifier, looks like a very low resistance on the input somehow.
 
I assume the AC voltage from the alternator also drops to almost zero when the rec/reg is connected?
 
To me that doesn't sound like an alternator problem.
 
You have checked the alternator stator resistance and that there is no short to earth, so the alternator seems good. If you put a very low resistance load on that alternator, the volts will drop and a very high current will flow, causing the wires to heat up.
 
So either you have a faulty rec/reg or somehow you still don't have it connected up correctly.
Brian.

Better 5 minutes late in this world than years early in the next.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Scousus maximus Quote  Post ReplyReply Direct Link To This Post Posted: 20 Jul 2017 at 19:38
Hi John,
Try this:

1 Regulator totally disconnected, run engine. Measure ac volts at yellow wires.

2 Connect regulator yellow wires only, does engine note change? what is ac volts now?

3 If engine note changes and volts drop fault is in the alternator or yellow wiring or regulator.

4 If engine note doesn't change and volts don't drop connect the other (dc) connector too.

5 If engine note changes and volts drop fault is in regulator and/or the wiring to battery.

6 If conditions at 5 are shown make a pair of jumper leads to go from regulator  pos and neg to battery pos  and neg. Include a 30 amp fuse and use decent size cable. This will by pass all the joints in  the  loom and should point to the fault. If battery volts are now good fault is in loom.

Take more notice of volts drop than engine note, a flat battery will cause some noise change as the charging circuit loads the engine.

Hope this makes sense and gets you sorted.

John


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Eibar-Jet200 Quote  Post ReplyReply Direct Link To This Post Posted: 21 Jul 2017 at 20:41
Will try tomorrow.
Thank you
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John
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Post Options Post Options   Thanks (0) Thanks(0)   Quote johnno Quote  Post ReplyReply Direct Link To This Post Posted: 21 Jul 2017 at 21:28
I mean no disrespect but you have not connected battery wrong way around even for a split second, sorry .
GSXR1100 L ,Moto Guzzi 650tt/ntx.750xpa,t5 850.1100 sport,1100 sport corsa rider
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Eibar-Jet200 Quote  Post ReplyReply Direct Link To This Post Posted: 07 Aug 2017 at 17:49
All,

The Breva is good again. Charging at 14.5v.
It was the Generator! Corroded and welded itself to the alloy casing. So looks ok when disconnected but died when all connected up.
£94 from M&P for a new one. Diagnosed and fitted by Roy at James Allan Motorcycles in Edinburgh. Top Guy!
Thank you for all your assistance.
Happy John    
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John
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 07 Aug 2017 at 18:04
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