Ducati Monster Forum

Known to foul plugs prompting a factory plug spec change to hotter plugs when oem were colder plugs than the 750/900 models was a band aid solution imo.

I worked on one recently and noted after much testing that concurrent issues contributed to plug fouling. The bike is stock but for heavily baffled Akrapovic pipes worth the cost of the bike itself. Seeing the pipes I initially thought someone had fattened up the jetting in the belief that its a compulsory mod. Nope, stock jets according to my chart.
The known needle jet wear issue is always a possibility. OEM hi comp pistons (don't you wish the 750/900 models had them) creating a more compressed mixture ignited by weak but otherwise fine oem coils, 750 jetting and large CV38 carbs with no accelerator pump all add to the picture.

The OEM Euro/Aus #40 pilot jets and132.5 mains made for great acceleration, but fouling at lower revs. That's 750 jetting. The Dynojet stage 1 kit has leaner specs by quite a margin (128DJ or 118-120 Mikuni). Our dense hi octane fuel from a certain brand and incorrect float levels didn't help.

Problem solved after much testing and some bad language in the workshop. Changed and reset float levels, 37.5 pilot jets, removed snorkles to the stock airbox, shorter rubber velocity stacks, Exactfit coils and NGK DPR8EA-9 plugs or DPR8EIX-9 iridiums for one step hotter  (and not the 7s the factory suggest). A fully open air box would require Mikuni 138-140 main jets so snorkles out at 132.5 really increased acceleration. Snorkles out is a mid way intake mod akin to a partially drilled airbox. 95 RON fuel rather than 98 also helped but it's a particular brand 98 that is the problem here in Australia.

So a number of solutions were applied as a combination which not only cured the problem, but improved performance and fuel economy. Its amazing how much difference one step in pilot jets affects economy with these carbs. The owner said the bike is much smoother but accelerates harder. They also noted more torque requiring less gear changes.

I think Ducati should have used Mikuni TM or Dellorto 36mm carbs on this bike.