Spark Exhaust Bent Tube 90° Ø 38 × 1.0 mm Stainless Steel Universal G9137

Thirty-eight millimetres at ninety degrees. The corner that gets a middleweight exhaust past the swingarm pivot, which on most machines is the point where a custom system either works or does not.

Key Features

• Mandrel-formed 90° bend, AISI 304 stainless steel.
• Ø 38 mm outside, 1.0 mm wall thickness.
• Straight tangents at both ends.
• Matches Spark's 38 mm straight tube, article G9007.
• Spark part number G9137, made in Mantova, Italy.

Past the Pivot

The swingarm pivot is a fixed point on every motorcycle, and the exhaust has to get past it while turning outward. There is rarely room for a gentle sweep there, so a right angle is what fits between the pivot and the frame.

Check the clearance with the swingarm at full compression rather than at rest. The gap that looks generous on a paddock stand is not the gap the pipe will have on a bumpy road with a passenger.

Order of Assembly

A right angle tucked against a frame member leaves nowhere to put a torch once the surrounding pieces are in place. Decide the welding sequence before anything is tacked: the joints that will become inaccessible get welded first, and the open ones last.

It is the usual reason a fabricated system has one bad-looking bead in it.

Heat Wrap and What It Does

Wrapping a bend keeps heat in the gas and off the surrounding components, and it also keeps moisture against the metal. On a road machine that combination corrodes stainless from the outside in, under the wrap where nobody looks.

On a track bike used dry it is fine. On anything that sees rain, a shield is the better answer.

Measuring the True Angle

A digital angle gauge held on the two straight tangents gives the real figure. Eye judgement does not, and half a degree at the first corner becomes a centimetre of misalignment at the silencer.

How Many a System Uses

Most one-off runs on a middleweight need one right angle and two or three shallower bends. Buying a spare of the ninety is worth more than a spare of anything else — it is the piece with the least margin for a mistake and the one that cannot be improvised from a shallower article.

Ordering

One bend per article. Spark builds 30°, 45° and 90° at this diameter, plus a 500 mm straight.