2008 Breva 750 Charging Issue

[GonzoB]

Hi Larry.

Following on from Muzz' input, here's the wiring diagram I have:



I assume you are taking your voltage readings at the battery terminal, point A, (as recommended by the manual). It would be useful to be able to take a reading at B - somewhere in the wire on the regulator side of the fuse - when the charging fails. If it's a faulty connection between that wire and the battery you should have 14V at B, and 12.7 at A. I don't know what the access to the wire is... you might have to force a pin through the insulation and put the alligator clip from the meter on it.

Anyway, if the voltage at B is down, it means the regulator failed, or the earth connection at C has failed.

Gonzo

[Momo]

I will be interested in the final outcome, as I am finding the figures somewhat bizarre.

AC figures remain constant..... equals alternator ok.
Charge figures ok for 5 minutes, then fall away. 

This second one is often a symptom of a failing capacitor.....but, to my knowledge there are no capacitors in a regulator.  A bridge diode setup in a regulator I wouldn't have thought would fall away.  Diodes don't usually do that.  May be wrong on that though.  Usually when diodes get electrical constipation and won't pass a current they die completely and don't even scream.  That would then show up as no charge at all. (Actually, it may show up as a half of the sine curve charging?)

I hope it is the regulator Momo seeing as you already have it , but if it doesn't, my suspicion is that a contact for whatever reason, is heating up over that 5 minutes and then breaking contact , whether it be verdigris, dielectric grease or a broken wire.

Best of luck anyway.

The weird part is disconnecting the battery when it stops charging, waiting a few minutes, reconnecting and the system works again for several   minutes.   Thanks for the input,    Larry

[Kiwi_Roy]

If you look at the diagram the charging circuit on the Breva is very simple,
I started to go over all the connections then noticed Gonzo B had them covered 2 posts back.
I think the fact you found some corrosion of the connectors is raising a red flag, possibly a loose contact causing an electrochemical reaction, consider bypassing that connector altogether as a test.
 

[Momo]

I'll replace the rectifier, then check voltage as suggested by gonzo.  I've been tied up working on my 77 El Camino providing long overdue maintenance so the Guzzi is in the background.   Appreciate the ideas and help, hopefully I'll have good news soon.   Regards,  Larry

[Momo]

Finally got around to working on the Breva.  After replacing the rectifier again and still experiencing the same scenario (intermittent charging) I decided to order a new stator.  This is what I found upon removal of the old one.  I now have to source a new or good used rotor.  Anyone have either the part number or a source?  Looks as though the end of the rainbow is in sight and I may be able to ride again, didn't ride at all last year.  Thanks again for all the responses,  Larry

[Momo]

Anyone know if rotor from a 2017 V7 Anniversario will work with my 2008 Breva 750?

[sign216]

Wow, looks bad.  Glad you found the problem.  Usually you can tell if parts will interchange by looking at the parts book; same parts carry the same numbers. 
That was true in years past, not sure if Guzzi maintanes that practice.

How about used units?

[80CX100]

     Harpers, MGcycle or Euromotoelectric, might be able to help you out, not particularly in that order, fwiw.

     Glad to hear you're on the right track, good luck

[Momo]

I've used MG Cycles for parts, great to deal with BTW, but they didn't have a rotor on their site.  I found the Anniversario one on eBay, waiting to hear back from them as to fitment.  I sent my measurements, the listing photo looks just like mine. If that doesn't work out there is a much more expensive used one listed.

Wish I could determine how that happened.  Only thing I can think of is either something was picked up or the stator retaining bolts were not fully tightened. 

Keep y'all posted,  Larry

[Muzz]

I suppose your front main bearing is ok Momo.  No play?

[Kiwi_Roy]

The rotor and stator should never make contact, you need to figure that out.
It's hard to see the damage properly, can you pull back a bit with the camera to get it in focus.
You should be able to get a stainless feeler or a thin aluminium shim in between the two parts all way around.
The friction is probably causing it to fail.
Like Muzz I'm worried about the main bearing.

[Momo]

Sorry for the long delay.  I cannot physically move the crank. I'll put a dial indicator on it when I get a chance. I did source a new generator unit from Harper's for $350-waiting on delivery.  Curtis(I think that was his name) from Harpers thinks someone may have had the stator off and reinstalled improperly. I also think that is possible as the bolts holding the stator in place were easily loosened.  His idea was to use business cards to shim the stator when installing.  Sound like a plan?  Thanks again for the replies,  Larry

[Scousus maximus]

Hi,
just a note about rotor compatibility between models. The later V7 alternator is an oil bath type and uses a totally different rotor configuration so NG for you. Check pics on Google to see differences from MK 2 onwards.

Just a thought, can that rotor be skimmed and still give a decent AC reading? I'd give it a go before spending money anywhere. (GC) You would still need to find how it got like that though,,,piece of debris through the front cover maybe?

HTH,

John

[Kiwi_Roy]

At least you have nailed down the reason for the failure, the alternators I have had apart it's virtually impossible to assemble wrong they just line up when bolted on.
The coils of the stator look kind of dark.
The V7 III alternators are completely different the stator is inside, the rotor outside and 3 phase, I had to replace mine because a couple of coils were shorted
, ,
Click to zoom

[MattP]

try this file the high spots off the rotor  sand off where it was rubbing on stator. It looks as if it was rubbing on one spot meaning the stator was off center and shorting out. reinstall with business cards as shims to keep on center. My bet it will work, cost nothing to try.Good luck Matt

[Momo]

I've already ordered the unit from Harpers Guzzi.  I thought of skimming the rotor and just replacing the stator but contrary to my frugal nature I ordered new.  I bought the bike for 2400 a bit more than a year ago so I rationalized spending 350-you know it means I only spent 2750 for the bike    Hopefully the unit will be here this week and I'll be back on the road.  I may have a friend trim the buggered rotor  and see how it works.  As always, thanks for the replies, Larry

[Momo]

upon closer inspection of the damaged  rotor I noticed this divot.  Could a piece have dislodged from the rotor?

[Momo]

still awaiting parts from Harpers

[Momo]

No.

(It was already mentioned in Roy's reply, but just in case you missed it.)

John Henry

Didn't miss, went ahead and ordered entire new unit from Harpers, along with yet another rectifier.  Been down now close to a year.  Thanks for the reply, Larry

[Momo]

Well,  contrary to all my previous years experience the alternator was bad.  Guess if I hadn't been so narrow minded I might have fixed the bike earlier(been out of commission for a year). Curtis Harper managed to get the entire unit at a somewhat reasonable price( I was thinking I might have to shell out close to a grand but the new unit was waaaay cheaper-much to my delight).  New unit installed using high-tech business card shims and I'm back on the road. 

Another problem I've incurred is manufacturer's suggested oil weight( I will not start an oil thread .  Page 45 of  the owner's manual says 5-40 but page 115 says 10-60. Never ran across such a wide discrepancy with UJMC. Another MG dilemma- Why are both ends of the driveshaft called transmission?    Anyhow, thanks for all the posts.  It's good to be back on the road, did a short 50 mile test run and all is well-that is after I figure out which oil weight to use,  Larry

[Muzz]

10W/60 every time Momo.  They can run very hot.

[Momo]

10W/60 every time Momo.  They can run very hot.

Thank you Muzz.  Regards, Larry