FOR THE DO-IT-YOURSELF DUCATI OWNER

CHANGING THE SPARK PLUGS

$5+

Torque Wrench (optional) or Ratchet, 18mm Deep or 5/8" Deep (Depending on Spark Plugs) Socket, Anti-Seize Compound

GENTLY remove the plug wire by firmly grasping the boot in its meatiest section (rather than the wire, which could rip out of the boot).

Next, take your 18mm (or 5/8") deep socket and extension and remove the plug, taking care that any debris that is down around the base does not get into the cylinder.

Take a rag and clean the head of any oil or other debris- you don't want that stuff in your engine.

One of the most critical and often overlooked steps when replacing plugs is gapping.  A plug's gap needs to be dialed in based on ignition modifications, etc.  A juiced ingnition needs a wider gap than stock, etc.  If stock, consult your underseat spec chart or shop manual for the proper gap, then use one of these handy gapping tools to measure.  Most of the time they come pretty close from the factory, but I've had some way off ones.  My engine is stock, so these were set to  0.65mm

Another common mistake is to leave the threads uncoated.   Here, I am rubbing on a little anti-seize compund.  Because the heads are not steel and the plug threads are, they can easily become seized and/or damage the head.  The compound is just a little extra insurance.

Next, screw the plug in until it barely touches the head, then stop and move on...

... to tightening.  The Ducati spec is 20 Nm (15 ft-lbs) for the plugs, but you can just as easily turn in the plug until it touches the head and go another 1/4 of a turn, they are basically the same spec.   Whatever you do, don't overtighten them because the crush washer will be destroyed.

Finally, you can press the plug wire back on and you're good to go.   If you want to you can add a little electrical grease to the tip of the plug to make it easier to remove the boot, but I've never found myself needing it.  I have the wires on and off all the time so there is no time for it to seize!  Now just move on to the other cylinder and you're done.

WHAT YOUR PLUGS ARE TELLING YOU: NORMAL= brown to tan coloring, with no wetness or black/white marks and only slight electrode wear.  Clean or replace. WORN= rounded electrodes, i.e. it looks as if they've been sanded or weathered.  The electrode should look crisp and edgy like it was when new.  Replace with new ones. RICH= dry sooty black coating over entire plug face.  Play with the mixture (start by leaning out idle) and replace plugs. WORN SEALS / RINGS= oils deposits on plugs.  Oil is leaking past the valve stem seals and/or piston rings and should be fixed.  Replace plugs. OVERHEATED PLUG / ENGINE= plug is white and 'blistered' from too much heat.  Either the plug is the wrong heat range or the engine is running too hot.  Check for an overly lean mixture, low oil / water level, vacuum leaks, or anything that would cause the engine to run too hot.  Replace plugs. PREIGNITION= melted electrodes and ceramic.  Ignition timing is most likely too far advanced, or the wrong octane fuel is being used.  Retard timing or increase fuel octane and replace plugs.  Could also be caused by an overly lean mixture or overheating engine (low oil level and/or water level).  Replace plugs GLAZING= cuased by sudden increases in combustion chamber temperatures (heavy acceleration).  Check that your carb's midrange jets/needles are rich enough or use a colder heat range plug.  Replace plugs. DETONATION= damaged plug, such as chipping, bending, etc.  Most likely caused by the wrong fuel octane or lugging the engine.  Also caused by the wrong plug gap (too wide).  Increase fuel octane / replace and correctly gap the plugs. WATER IN COMBUSTION CHAMBER= white plugs.  A fluffy white coating indicates water in the gas or a coolant leak on liquid cooled engines.  Replace plugs and add water remover to tank.

This page is in no way associated with Ducati.com, nor is it an entity of Ducati Motor Holding, S.p.A.  All content, information, and views expressed herein are those of myself and do not reflect those of Ducati or its affiliates.  The "DUCATI" logo and "Circle D" are registered trademarks of Ducati Motor Holding, S.p.A., all other content on this website is copyright 2006, Monster Man Productions.

Replacing your spark plugs is a very simple task and should be done
regularly.  A fouled or damaged spark plug can cause serious loss of
performance, hard starting, misfiring, and poor fuel economy among
other things.  Even if you don't replace them it is a good idea to inspect
them regularly- you can learn a lot from your spark plugs about how
the engine is running (see bottom of page for more).  The first step is
to lift the tank and/or remove any fairings that block access to the
upper cyclinder.  Simple enough

On a 4 valver you  have to
remove the fairings, front
v-piece and tank to access
the plugs, and you need the
long tool from the toolkit to
remove them.  You can slip
a 14mm wrench or socket
over the end.  Or, you can
take a deep socket and grind
the edges down thin so that
it fits in the small hole in
the head.  You'll need to if
switching

from the stock Champions because the Champions use a smaller hex size (5/8" or 15mm I believe) and other plugs
use a larger one (mostly 18mm), and a regular 18mm deep socket has too thick of a wall to fit down in there.