Spark Exhaust dB Killer Round and Megaphone 34° 28 Holes Ducati Monster G9914

Twenty-eight holes and a thirty-four degree seat. The most steeply angled insert Spark builds, for the round and Megaphone cases — and the one it names the Ducati Monster against.

Key Features

• dB killer for Spark round and Megaphone silencers.
• Ø 47 mm outer, 32 mm internal bore.
• 34° seat angle.
• Perforated: 28 holes.
• Listed by Spark for Ducati Monster applications.
• Stainless steel, removable.
• Spark part number G9914, made in Mantova, Italy.

Twenty-Eight Holes Instead of a Straight Bore

A perforated insert works differently from an open one. Instead of narrowing the exit to a single smaller opening, it makes the gas pass through a wall of small holes, breaking the column up before it leaves. Total flow area can be similar; the acoustic result is not.

Perforation kills more noise for the same restriction, and it changes the character of what is left — less edge, more body. On a big V-twin that is usually what the owner wanted in the first place.

Thirty-Four Degrees

That is a steep seat, and it exists because the cases this fits are cut at that angle. Trying to fit an 18° insert into a 34° outlet leaves a gap on one side; the part will not seal and it will not stay.

Angle first, then bore. It is the order to check in when you are matching an insert to a silencer you did not buy new.

Named for the Monster

Spark lists the Ducati Monster specifically against this article, which tells you where most of them end up. The Monster's round Spark cases take exactly this geometry, and a Monster is also the kind of motorcycle whose owner is likely to need the insert at some point.

It is not a fitment restriction. Any Spark round or Megaphone case with a 34° outlet takes it.

Not a Legal Fix

The insert changes the reading on a sound meter. It does not create a certificate, and it does not turn a Custom Works silencer into a homologated one. That distinction matters at a technical inspection and it is worth being clear about.

One Per Silencer

Order one for each case. A Monster running two Spark round silencers needs two of these — same article number twice, since the part is symmetrical.