Spark Exhaust Stainless Steel Tube Ø 35 × 1.0 mm 500 mm Universal G9011

Thirty-five millimetres of straight stainless, half a metre at a time. A size that sits between the small-bore work and the middleweight sizes, and gets used for both.

Key Features

• Straight exhaust tube, AISI 304 stainless steel.
• Ø 35 mm outside, 1.0 mm wall thickness.
• 500 mm long.
• Sold as fabrication stock.
• Spark part number G9011, made in Mantova, Italy.

A Size With a Silencer Behind It

Thirty-five is the internal bore of Spark's Force db killer for small twins — the one it names against the Yamaha R3 and Kawasaki Ninja 400 — and of the Moto GP inserts. Those are the machines and the silencers this tube diameter suits.

On a 300 to 500 cc twin it is a reasonable link diameter. On a litre bike it is a restriction.

Fitting Tube to Tube

Two pieces of 35 mm tube cannot be pushed into one another; the outside diameter is the outside diameter. Joining them means either a butt weld, a sleeve made from the next size up, or a swaged end — and on a one-off system the sleeve is usually the honest answer, because it is the joint that can be aligned before it is welded.

Spark's own systems use slip joints for exactly that reason. A butt weld looks better and forgives nothing.

Heat Tint

Stainless colours where it has been hot. On a finished exhaust that is normal and eventually attractive; on a weld it is a diagnostic. A straw or light-gold tint next to the bead is fine; a grey, powdery band means the weld got too hot and the chromium has been drawn out of the surface.

That band will rust. Pickling paste removes it if you catch it early.

Bends in This Diameter

Spark offers 35 mm as a ready-made 30°, 45° and 90° bend — articles G9129, G9130 and G9131. Between those and this straight length a complete small-bore run can be assembled without bending anything in the workshop, which matters because thin-wall stainless is unforgiving of a bad bend.

Half a Metre at a Time

Spark supplies this in a single 500 mm length. Most link pipes need less; most full systems need more than one. Order accordingly, and cut generously — a piece can always be shortened.