The exhaust manifold is first in line for everything the front wheel throws up: dust, tar, insects, mud spray. Heat bakes these deposits into a hard dark crust that a normal wash will not shift.
You can bring the headers back to factory condition at home with water, steel wool, a few sheets of wet-and-dry paper and a little patience.
What you will need
- A sponge and rubber gloves
- 000 steel wool
- A drill or driver with a soft polishing brush (optional)
- Wet-and-dry paper in P180, P280, P500, P1000
- Several microfibre cloths
- WD-40 Multi-Use or WD-40 Smart Straw
- Metal polish
Important: Work only on a completely cold engine. Use abrasive paper and steel wool only on unpolished stainless or mild steel, and never dry; chrome, painted and ceramic-coated headers must not be abraded.
Step 1
Pre-wash the manifold
Rinse soil, tar and insects off the manifold and the whole exhaust with an ordinary hose. Avoid pressure washers: they force water into joints and connectors, which encourages corrosion. Wipe with a sponge and warm soapy water, rinse and dry with a cloth.
Step 2
Soften deposits and use steel wool
Apply WD-40 Smart Straw to the manifold: the thin straw reaches pipes tucked between frame and engine. Rub with steel wool according to how dirty it is to remove stubborn stains.
To save elbow grease, use a drill with a soft finishing brush. Do not press hard: let the brush and the product do the work, as excess pressure leaves scratches.
Step 3
Sand the worst areas
For heavily baked deposits, cut a small piece of P180 and sand the problem spots, keeping them wet with WD-40 Multi-Use. Wipe with microfibre, check the result and repeat with P280, then P500. Once the surface is even, go over it with P1000 and finally steel wool.
Step 4
Bring back the shine
Apply metal polish to the manifold and buff with microfibre. Repeat with clean cloths until no more dirt comes off on the fabric and the metal has an even shine.
Step 5
Dry and protect
Dry the manifold and the bike thoroughly: moisture in the joints is the main cause of corrosion. Give clamps, studs and fixings a light coat of WD-40 to drive out remaining water, and wipe off the excess. A little smoke on the first warm-up is normal.
Tip: A freshly cleaned stainless manifold will show heat colouring again after a few rides. That is the metal's natural reaction to temperature, not dirt, and it cannot be fully avoided.
What next
Repeat the wash and protection after every dirty ride, and do the full abrasive clean once a season. Workshops servicing many bikes will find WD-40 5 l with sprayer more practical. Clean the silencer following our separate guide.
These uses come from the experience of WD-40 users in many countries. Always follow the instructions and warnings on the product label.
More guides in «How to use».