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Thursday, April 9, 2015

ST3S Major Service

Here's an ST3 that's in for its 15K service.  The bike was recently bought by its current owner but it had no service records.  It's a 2006 model so it has the quiet, long-lived wet clutch in place of the damnable, noisy dry unit that "Ducatisti" are so fond of hearing.  Personally, I prefer that a bike not sound like it's self-destructing, but that's just me.  It's also an "S" model so it gets the (OEM) Öhlins shock along with ABS.  I think that the ST2 and 3 were the best bikes that Ducati ever built and can't fathom Ducati's decision to discontinue the line.  There are a couple of other things about this particular bike that I also can't fathom which I will detail presently.

Stripping the bodywork to access the engine....

Apparently, putting a dab of anti-seize on the fairing fasteners just takes too much time for the average flat-rate wrench-monkey, so we end up with fairing screws rusted to the wellnut inserts.
They either don't come out at all...
...or they tear the insert
Obviously the wellnuts will all be replaced and the fairing screws will be lubed to prevent this in the future.

Then I lifted the tank and found this.  A fine example of "tuning" using the advice of internet "knowledge" and a healthy dose of mechanical incompetence.

If you're thinking that having the air filter loosely held in place with wire would allow dirty, unfiltered air to enter past the filter, you would be correct.
The internet forum experts continue to have no idea as to the actual function of the airbox in a modern motorcycle.  This isn't some old POS American car in which the air cleaner housing can be removed for "free horsepower".  The airbox of a modern bike is an integral part of the bike's intake system.  Its volume and rigidity are engineered to produce a resonance that boosts intake pressure at a certain RPM.  Removing the lid destroys that, as does removing the snorkels (which actually convert the incoming air's velocity into pressure) or cutting holes into the lid.  Unless you've got a degree in fluid dynamics and can understand airflow behavior in an IC engine, DON'T assume that you can successfully second-guess the engineers that designed your bike (I'll save you the suspense, you can't).

As has been known forever, K&N filters DO flow more air than stock paper filters.  How do you think they do that?  It's no secret that the more open mesh that allows more airflow also provides LESS FILTRATION.  Again, in the case of a modern bike, the OEM filter is not a restriction.  The paper filter has much more surface area than a gauze filter (that's why it's pleated, cut one out and flatten it, you'll see just how big it really is) and it actually stops the dirt particulates that turn into grinding compound in your engine.

This is what was inside one of the intake trumpets...

Ducati did not leave you any "free horsepower" to be discovered by butchering your airbox or installing a less efficient filter.  You are MUCH more likely to find a bit more power by correcting the factory's cam-timing errors than anything else.

Here are the new airbox lid and intake snorkels, fresh from Italy.  Notice the inside diameter of the intake snorkel compared to the size of the hole in the lid.  If you think that the airbox will flow more air with the snorkels removed, you'd be wrong.  Airflow does not like sharp edges.  Notice the radius at the inlet side, this smoothly guides the incoming air into the even narrower throat, thus causing an increase in flow velocity, just like Mr. Bernoulli discovered it would.

It's at the outlet side of the snorkel that the air's velocity is converted into pressure, just as Mr. Venturi discovered.  The outlet side is a gradual taper outward.  This is known as a diffuser (not a de-fuser, that's somebody who works on the bomb-squad) and is designed to convert the velocity of the air in the venturi back into pressure with minimal energy loss.

Here is a comparison of the stock versus the K&N (crap) air filter elements.  Notice how the paper air filter has many more pleats.  This equals more surface area.  Imagine pulling both filters out flat and you'll get an idea of just how much more.  The stock air filter is not a restriction, it's surface area is calculated to provide sufficient air flow for the engine while maintaining better than adequate filtration.  As I stated earlier, the K&N will flow more air, BUT will do so at the expense of filtration efficiency, and an otherwise stock engine has no need of more airflow.




Apparently, the valve clearances had never been serviced as they were ALL out of spec on both the openers and closers.  Both exhaust valves had ZERO clearance on the openers.  This is a dangerous condition since the exhaust valve depends upon full seat contact for not only sealing but more importantly, for heat transfer from the hot valve to the cylinder head where the coolant can carry the heat away.

Since any job that's worth doing is worth doing right, I always take the time to set the closer clearance to .001" to .002" on every Duc that comes into the shop for service.  I also set the opener clearance to minimum end of the factory specification.  This makes for a quiet valvetrain that does not depend upon the helper springs to close the valves at idle.  Sometimes, in order to set the clearances with such precision the shims must be ground by hand to the proper size.  On this job two closers and two openers had to be custom fit.  I usually use a #2 cut file to get them close and hand lap to finish.  Here is the setup for hand lapping the shims.  It is a steel master flat surface plate with a thin coat of oil to hold the paper in place.  The paper is lubricated with a couple drops of oil to create a slurry and it leaves a perfect finish on the face of the shim.

Here is the rear exhaust shim stack in place.  Removing the cam bearing block and the opener rockers makes the job much easier than simply sliding the rockers to the side and doesn't take much more time.

With the valve clearances corrected and the new timing belts installed and correctly tensioned it's time to hook up the computer and test all electrical components relating to the engine (injectors, cooling fan, etc.), check for trouble codes, set the TPS and clear the service reminder.

With the engine warmed up the final operation is to change the engine oil and filter and check and clean the pickup screen.  The pickup screen should never be neglected since it is the oil pump's first defense against particles that could damage it.  This screen looked good but that cheap-o oil filter is a bad choice.  OEM filters and Mobil-1 oil are the only items that I will use.  The filter is pre-filled before installation.  This greatly reduces the time that it takes the oil to reach the valvetrain after start up.  As standard practice I safety the new filter with a hose clamp on all Ducati service.


Finally, the bike is detail washed, the bodywork is reinstalled and the bike is ready for another 15 thousand miles of trouble-free riding.