Ducati Sporting Club UK > Model Specific - Discussion, Technical Problems and Help > 998 / 996 / 916 / 748 > 916 Regulator/Rectifier possibly shot?

[Lust4Life]

Hi all,

I know this one has been done extensively and I've had a quick read through the old posts.

I just wanted to post up my particular symptoms before I order a new RR51 in case it's anything else and I'm being dumb!

Firstly, I've attached a picture of my current R/R as I'm not sure if it is the early or late type. (I know it's undone with the earth strap off, I was re-fitting it after checking all the wiring when I took the picture )

Basically the bike runs fun with the lights off and I can blat round as much as I want.

On the way home from the cafe on Wednesday it was getting dark so I switched the lights on and it started playing up, misfiring etc. within a mile or so and stalled shortly after. I managed to get it home after a bump start but it was running like a bag of nails (much to my wifes amusement when I got home )

I've checked all the wiring and it's all fine, nothing melted, shorted or anything but the R/R does run very hot even at idle.

I decided to re-locate it under the seat unit to get it away from the exhaust and it still runs hot even at idle. It also does not appear to be pumping much more than 0.5v into the battery @ 3k RPM but the battery is fully charged and very healthy so I'm not sure if it should. I can't seem to get it over 13v though so I don't think it is charging.

Took it out again yesterday and everything was fine, she is a little honey, and on my way back, about a mile from home, I decide to turn my lights on after maybe 60-70 miles total riding and within 100 yards she is popping loudly on overrun. About 200 yards after that, even though I switched the lights off almost immediately, she starts running rough and I barely get it home - stalled about 50 yards from my door

To my mind it is either battery, R/R or generator/stator.

The battery appears to be fine, charges well and holds 12.4 volts no problem.

I can't see any obvious problem with the generator/stator so it has to be the R/R?

Sorry for the long post, I just want a bit or reassurance before I order the new one later today.

Many thanks!

Phil

[rockhopper]

Do you have to re charge the battery each time this happens? With the motor running there should be about 14.5 volts across the battery at 3000 rpm. Significantly less than that then you have either an alternator or regulator problem i think.

Is the engine quiet? Is there any noise from the left hand side that doesnt go away when you pull the clutch in?

[HW]

I am thinking that this is not just a regulator problem. Rockhopper is right that there should be over 14V across the battery when charging, and on mine I think there is 11.7V when engine is off.

The other symptoms you describe seem to suggest there is something mechanical going on too. Was it only the STs that had alternator rotor nut problems? I do not know enough about the 916 series to comment.

A short in the alternator coils would also cause problems with the "back EMF" which would have a tendency to fight against the engine. Not sure how much that would be noticable and give you a feeling of "running like a bag of nails".

We're sure this is "bag of nails" is not normal Ducati clutch rattle? My ST2 was described as "dragging a shoping trolly down the street"!

[Felix]

Phil, yours is the old style. If you fit a new style or the RR51 from Electrex, I would also fit the heat sink that the newer bikes have.

Electrex have a nice fault finding chart here. I'd start with that.

[rockhopper]

The ST4 shares the 916 engine (mostly) so suffers the same nut problem. Its even cropped up on at least two M600's that i know of.

[Lust4Life]

Cheers guys.

The rough running is as though the ECU has gone into 'limp home' or safety mode.

Massive bangs on overrun, very hard to accelerate, won't idle and flames out of the exhaust!

The battery is fit and I do keep it on a trickle charger, it has needed recharging after both of these rides.

It runs absolutely beautifully before I turn the lights on which makes me think the additional load is more than the battery can handle because the R/R does not seem to be contributing enough to charge the battery.

Is there a quick, visual way I can check the alternator nut? It was serviced 500 and 900 miles ago by 2 different dealers (big £'s) and given a clean bill of health each time.

Cheers!

Phil

[rockhopper]

I dont think the ECU has a limp home mode, its not that sophisticated. Sounds like there isnt enough juice to keep the fuel pump etc running.

Depending on how loose the nut is you might be able to see bits wobbling through the left hand sight glass or there might be a noise that doesnt go away when you pull the clutch in.

You need to check what was actually done at each service, they dont all do the nut unless you ask them as the side cover needs to come off which means dropping the oil and coolant.

Really sounds just like a cooked regulator.

[Lust4Life]

Agreed, I'm going to run through the fault finding chart that Felix pointed to and go with a regulator initially if it points that way.

If that doesn't fix it I can then move on (probably to a specialist) and get the other bits checked out.

Any other thoughts still appreciated though.

Cheers!

Phil

[rockhopper]

Check the earth connections are sound including the engine earth strap.

[Lust4Life]

Originally posted by rockhopper
Check the earth connections are sound including the engine earth strap.

Good point, I've already redone the ones to the R/R when I moved it.

Phil