Spark Exhaust Stainless Steel Tube Ø 32 × 1.0 mm 500 mm Universal G9006

Thirty-two millimetres, one millimetre of wall, five hundred long. The first size in Spark's range built to the thin-wall standard that runs through the rest of it.

Key Features

• Straight exhaust tube, AISI 304 stainless steel.
• Ø 32 mm outside, 1.0 mm wall thickness.
• 500 mm long.
• Fabrication stock, supplied uncut and unwelded.
• Spark part number G9006, made in Mantova, Italy.

One Millimetre of Wall

From thirty-two millimetres upward Spark builds its tube at a one millimetre wall, and holds it there all the way to sixty. That is a deliberate choice rather than a cost decision: an exhaust tube carries almost no structural load once it is hung properly, and every gram above what the job needs is a gram hanging off the back of a motorcycle.

It also welds better. A thin wall reaches temperature quickly and evenly, which is what a clean TIG bead needs.

Where 32 mm Belongs

Small twins and singles. It is a common header diameter on 250 to 400 cc machines and a sensible link size where the standard system used something similar.

It is also the internal bore Spark uses on several of its db killers — the Classic, Sinfonia, GP Style and round-case inserts all run 32 mm. That is a coincidence of design rather than a compatibility note, but it gives a sense of the gas volume this diameter is meant to carry.

Gas Speed, Briefly

Diameter sets velocity for a given flow. Too large and the gas slows, scavenging suffers and the engine loses bottom end; too small and it chokes at the top. Matching a link pipe to what the engine actually produces is the whole reason a range of diameters exists.

If you are unsure, the standard system is the best available evidence: measure what the manufacturer used and start there.

Handling the Material

Stainless is easy to mark and hard to polish out. Store the tube capped and off concrete, cut it dry, and keep the file you use on it away from mild steel — embedded iron particles are what makes stainless rust in patches.

Weight Against Titanium

Stainless is roughly seventy per cent denser than titanium, so an identical part comes out that much heavier. It is also a fraction of the price, forgiving of a second weld, and repairable by any competent workshop. On a custom build those three things usually outweigh the grams.

Ordering

One article, one 500 mm length. Order as many as the project needs; Spark does not supply this in other lengths.