Ducati Sporting Club UK > Model Specific - Discussion, Technical Problems and Help > 998 / 996 / 916 / 748 > Its broken down again!

[Shazaam!]

The most common reason for a low alternator voltage output measurement is that the stator lead wire insulation is heat damaged. To diagnose this, strip away the common sheath that the stator wires run in and then separate the wires from themselves and from any grounded component. Then re-measure their output AC voltage. Examine the insulation for any softening due to heat damage that will cause them to short together at voltage levels lower than the alternator's rated output level. It's rare to see failed stator windings, but it's very common to see stator lead wires overheat and damage their insulation - because Ducati has supplied seriously under-sized wires - given that they have to carry 30-plus amps. Replacing the wires with a heavier gauge between the stator and the regulator cures the low voltage problem.


http://ducatisportingclub.com/contro...d.php?tid=2042

[Billythekid]

oh right ok, had a look at as much of them as i could see and they seemed fine, no continuity between thrm and ground as well

[Shazaam!]

No, they short together, not to earth. The insulation on my stator wires was so damaged from the copper in the wires getting too hot that I could scrape off the insulation with my fingernail. Same sub-12 voltage output that you describe.

The wires are held in contact with each other along almost their entire lenght by the sheath and the damaged insulation can't isolate the two wires at the alternator voltages produced at higher rpm. So no charging occurs and after 20 miles or so, the battery discharges completely and the erratic tach/stall problem develops. Take the sheath off and replace the wires with a heavier gauge.
This is a design deficiency that every Ducati pre-1999 superbike owner should correct before these problems develop.

[Billythekid]

Yep fair one, Im on it. Time is running out rapidly for me now though. Im out the country with work for anout 7 months, leaving in a couple of days. I only wanted one last blast on it!

Joel

[DC]

Hello mate,

i know that bikes can seem a pain when things go wrong. But dont give up on the Duke yet! Its easy for me to say this cos im not the one pullin me hair out.

Just stay with it. Once you get it fixed you will be in love with the bike once more.

[moto748]

I've read this thread (and Shazaam's linked thread) with great interest.

A week ago my battery (apparently) clapped out. Went to start it after work, and dead as a dodo, tacho needle spinning when the starter button pressed. I use the bike (2001 748) regularly, and have had no charging/electrical problems in the past. As a MY2001 bike, I had the gel-type battery fitted. I got it replaced with the conventional lead/acid YB16LA2.

All seemed well until I went out for a spin this sunny Bank Holiday afternoon, and sure enough the same thiung happened when I stoppped for petrol. When the breakdown guy eventually arrived he got it going no problem with his booster pack, but said the charging system was faulty (I'd managed to figure this out myself ) . So I said "regulator/rectifier?" and he reckoned more likely alternator (but hopefully it's just the wiring as mentioned above).

He also made some comment about swapping the gel-type battery for a conventional one, and wondered if the charging system was compatible with either. Do anyone know if the change from lead/acid to gel-type batteries was accompanied by any change in the rect/reg, or other electrical components? Also I have to say that the guy who sorted me with the battery is an experienced Ducati mechanic, and I'd be surprised if he wasn't fully genned up on this.

Anyway, I'll give him a bell on Tuesday and see what he says.

[Shazaam!]

[quote]Originally posted by moto748

anyone know if the change from lead/acid to gel-type batteries was accompanied by any change in the rect/reg, or other electrical components?


In 2001, the bikes were fited with a revised starter motor gear ratio that drew less current and made it possible to start the bike using a smaller battery. The starter gearing on the early bikes is not well suited to the smaller batteries.

Standard battery 1994 - 2001 model years:

Yuasa YB16AL-A2 (16 AH, 200 CCA, 11.5 lbs.)

Standard battery 2001 - model years:

Yuasa YT12B-BS (10 AH, 125 CCA, 7.6 lbs.)

[Edited on 4-12-2004 by Shazaam!]

[moto748]

but nothing you've said there precludes me from fitting the 16Ah battery to my 2001 bike, does it?

Anyway, it's going into dock tonight. Hopefully it's nothing more thsn the wiring. I'm told 3-phase alternators are v, expensive, but that they very seldom fail. it's all for the best anyway cos I'm treating it to a new clutch and chain and ally sprocket set.

Funny that in 65000 miles done lately on Ducatis, this is my first electrical/charging circuit problem!

Some would say I've just been lucky!

[rockhopper]

You've just been lucky.

[Shazaam!]

[quote]Originally posted by moto748
but nothing you've said there precludes me from fitting the 16Ah battery to my 2001 bike, does it?


No, the YB16AL-A2 is an excellent battery. Batteries are rated and compared using their amp-hour (AH) and their cold-cranking amps (CCA) capacity. The higher the AH rating and the CCA rating, the better. The only real downside in selecting a bigger battery is weight. The higher capacity batteries are proportionally heavier.

The AH rating is a measure of reserve capacity. A 16AH-rated battery can produce one amp of current flow for 16 hours, or two amps for eight hours, or 16 amps for one hour, etc. A 10AH-rated battery can only supply about 60% of that. So if you let your bike sit for a month without being on a trickle-charger you'll have a (10-15% less each month) reduced reserve for starting because any battery will self-discharge. Once the bike is started, if you don't ride long enough to fully recharge, you'll be down on CCA's the next time you try to restart.

A 200 CCA-rated battery by definition can supply 200 amps for 30 seconds at 0ºF. We usually don't start our bikes at such low temperatures, but the rating is still informative because it gives a measure of the battery's capability to supply the high current needed to turn-over the engine in less-than-ideal conditions. For example, a fully-charged battery at 80ºF can supply only about 60% of the CCA-rating when the temperatures drop to 32ºF. Further, the CCA-rating of a battery drops as it ages, until it can no longer supply an adequate current to spin the starter fast enough to start the motor. That's when you need a new battery. That's also why the higher the CCA rating, the longer the battery can be expected to last.


As an alternative to a lead-acid battery, there are a couple of maintenance-free batteries worth mentioning because they exceed the AH and CCA capacity of the Yuasa YB16AL-A2 standard battery.

Fiamm-GS F19-12B (19 AH, 200 CCA)

Odyssey PC680MJ (19 AH, 280 CCA, 14.7 lbs.) - dry cell technology, my personal choice.

On the track, weight reduction is more important than these other considerations so the weight-saving battery-of-choice is the sealed and non-spillable AGM maintenance-free Yuasa YTZ7S. It's the same size as the later-year stock battery.

Yuasa YTZ7S (6 AH, 130 CCA, 4.6 lbs.)