| One thing to check is your cam timing. Ducati 8-valve models can have cam timing variations of as much as 8 degrees crankshaft, right from the factory. This definitely will make a bike harder to start. Correction is done by advancing or retarding the cams using either offset keys or adjustable pulleys. High-lift short-duration cams seem to be less affected than do the longer-duration cams when off a few degrees. Street Ducati's commonly gain anywhere from two to five HP depending on how far the stock cam timing is off.
When Ducati changed to a smaller battery for the 2001 model year they also changed the starter gear ratio to reduce the starting current demand in order to match the lower current rating of the new battery.
Standard battery 1994 - 2000 model years:
Yuasa YB16AL-A2 (16AH, 200CCA, 11.5 lbs.)
Standard battery 2001 - model years:
Yuasa YT12B-BS (10AH, 125CCA, 7.6 lbs.)
The AH-rating is a measure of reserve capacity. The earlier 16AH-rated batteries by definition can produce one amp of current ?ow for 16 hours, or two amps for eight hours, or 16 amps for one hour, etc. The later 10AH-rated batteries can only supply 62% of these figures. 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 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.
The earlier 200CCA-rated battery by definition can supply 200 amps for 30 seconds at 0º F. 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 80º can supply only about 60% of the CCA-rating when the temperatures drop to 32º. 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.
The principal advantage of using a larger capacity battery is to be able to restart repeatedly. When you don't ride long enough to recharge fully between restarts, a larger capacity battery is an advantage. A lower capacity battery will need to be trickle-charged more often and the chance of a deep discharge (that reduces battery life) is greater with small capacity ones. Further, a battery's capacity drops when it gets cold so when you ride in cool weather, a smaller capacity battery will have an even smaller reserve for starting at low temperatures.
Here’s an analogy that will help. Consider two buckets having a spigot at the bottom with water in them. The first bucket is one foot in diameter, the second is two feet in diameter. They are both filled to a depth of one foot of water. The pressure (voltage) at the bottom of both buckets is the same, so, when you open the spigot, the flow of water (current) is the same. Consequently, the amount of water they can supply per unit time (CCA) is initially the same. However, the smaller bucket has less water in it, so it will empty sooner (AH.)
How much current is needed for a start, the reserve needed for repeated starts, and the charging system capacity for the expected range of operating temperatures is determined by Ducati when they design the electrical system. In general, a larger capacity battery is a lot kinder to the charging system components, particularly the regulator/rectifier.
In particular, that the early pre-1998 bikes have an alternator with a lower charging current output, so they'll take longer to fully recharge the battery. A prolonged 30 amp charging current is one contributing factor to why Ducati voltage regulator/rectifiers and stator wires fail prematurely.
On the track, weight reduction is more important than these other considerations so the weight-saving battery-of-choice is the sealed and non-spill-able AGM maintenance-free Yuasa YTZ7S. It's the same size as the later-year stock battery. The weight saving it offers is probably equivalent to $1000 in carbon fiber replacement parts, and about $3000 in titanium exhaust pipes and fasteners.
Yuasa YTZ7S (6 AH, 130 CCA, 4.6 lbs.)
On the street, reliable operation is of a higher concern to most of us, so consider the following maintenance-free replacement batteries for the (physically and electrically) larger 1994 - 2000 model year stock Yuasa YB16AL-A2:
GS Battery GT12B-4 (12AH, 200CCA, 10 lbs.)
These batteries, although having a lower AH-rating, seem to have much more go than the old YB16AL-A2. They spin an SPS with the cam timing reset just fine, where the YB16AL-A2 will have a hard time if not fresh.
Odyssey PC680MJ (19AH, 280CCA, 14.7 lbs.) (dry cell technology, my personal choice)
I don’t know the exact specs on the Ducati starter motor, but in general, motorcycle-size starter motors draw around 30 amps under no load (max rpm) and around 85 amps under typical starting torque loads for unmodified motors. However, this figure can briefly rise to 300 amps under a stall condition typical of the initial start requirements of a high compression motor - like the SPS.
If you look at the wiring running to the starter motor you’ll see that Ducati made a trade-off between cost and weight vs. electrical resistance. The higher the resistance, the lower the current that is delivered to the starter motor and the more electrical heating of the wiring. The lower the current delivered, the harder it will start.
Sizing the battery and starter cables for at least 100 amps seems more reasonable to me. A number of 996R owners have reported easier starting after they replaced these wires with a larger gauge.
But before you replace any wiring, first check the circuit for points of high resistance, Corrosion at the connection to the starter motor is the prime suspect because water often collects in the rubber boot covering the connection. Clean the connection anyway and then fill the boot with dielectric grease to keep the water out.  |
24-Sep-2004, 16:16 
Shazaam!
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