Spark Exhaust dB Killer Moto GP 35 mm 21 Holes Universal G9941

The perforated insert for Spark's Moto GP case. Twenty-one holes through a thirty-five millimetre bore, in a body wide enough to seat in a case built around its own width.

Key Features

• dB killer for Spark Moto GP silencers.
• Ø 57.5 mm outer, 35 mm internal bore.
• Perforated: 21 holes.
• Stainless steel, removable.
• Not supplied with the Moto GP universal silencers — order it separately.
• Spark part number G9941, made in Mantova, Italy.

The Perforated One of the Pair

Spark builds two inserts for the Moto GP case at this bore: this one with twenty-one holes, and G9969 with a plain open bore. Same outer diameter, same silencer, different acoustics.

Take the perforated version when the venue's limit is tight or the engine is large. Take the open one when the reduction needed is modest and you would rather keep the flow.

Fifty-Seven and a Half Millimetres

That is a wide insert by Spark's standards, and it follows from the case. The Moto GP silencer gains its volume across the width rather than along the length, so its outlet is correspondingly large and the plug that seals it has to match.

Nothing else in Spark's range shares the figure. An insert from a round or vintage case is fifteen millimetres too small and will not seat at all.

Twenty-One Holes

The number is a compromise Spark arrived at for this specific case volume. Too few holes and the insert becomes a restriction that costs mid-range; too many and it stops attenuating. Twenty-one, at this bore, in this case, is where the two curves cross.

Buy It With the Silencer

Spark's Moto GP universal silencers — G00SI08T for the right side and G00SI09T for the left — ship without an insert. If your build will ever see a circuit with a noise check, add this article to the same order rather than discovering the requirement at the gate.

One Per Case

Symmetrical, so left-hand and right-hand Moto GP silencers take the same article. A twin-can installation needs two of this number, not one of two different ones.

Racing Part, Racing Status

The Moto GP case is sold as a racing article with no homologation, and this insert does not change that. It exists to satisfy a circuit, not an inspector.