CYLINDER RESTORATION

Re-chroming restores the internal surface coating (Nickel–Silicon) when the original coating is heavily worn, damaged, or detached in places.

Being an artisanal process, the quality and adhesion to the aluminium’s porosity make it more durable than typical mass-production coatings.

The process includes:

• removal of the previous coating using mild acids and bases (inert to the aluminium)

• stress-relief heat treatment to avoid residual tensions

• turning the bore to restore perfect cylindricity and perpendicularity to the head planes

• deburring of the transfer passages

• electroplating bath to apply the new coating

• sandblasting to remove residues and ensure a perfect surface finish

• heat treatment to verify perfect adhesion

• honing to size and t-shape finish

The price refers only to the operations listed and excludes additional work such as exhaust bridge radiusing, welding, etc.

Honing restores the Nickel–Silicon coating to perfect cylindricity with a very low surface roughness.

The cross-hatched micro-grooves (t-shape) retain oil and ensure optimal lubrication in operation.

This is required whenever a piston is replaced to match the new piston with the correct clearance and a properly restored inner surface.

Radiusing of the exhaust bridge is required after the re-chroming process on 2-stroke cylinders featuring a bridge exhaust.

The bridge, exposed to hot exhaust gases and being thin/elongated, runs hotter and expands more than the cylinder.

Anchored at top and bottom, it can only expand towards the cylinder axis.

In operation, this would quickly damage the piston and reduce its lifespan.

We pre-relieve the bridge by a few hundredths depending on model and displacement.

At operating temperature, the bridge aligns with the bore, ensuring proper function and piston durability.

For severe seizures that also damage the aluminium base, once the coating is removed, aluminium is added by welding to restore the original shape.

Given the delicacy and assessment difficulty (especially for severe damage), it’s best to inspect the cylinder after de-coating to gauge the real extent.

The process includes stress-relief heat cycles to avoid distortion or post-weld cracking.

Welding costs exclude re-chroming, which is necessary because welding is performed on a de-coated cylinder.

In case of heavy seizures on cylinders with an exhaust bridge, cracking may initiate inside the bridge.

If detected (usually after de-coating), we offer complete reconstruction to restore the top-end’s proper function.

The service includes: partial/total removal of the bridge, addition of new material by welding, hand re-profiling to restore the exhaust duct geometry, and final heat cycles for stress relief.

Reconstruction excludes re-chroming and radiusing, which are necessary because the work is done on a de-coated cylinder.

WARNING: Honda CR125 (2000–2004) and CR250 (2002–2004) cylinders suffer a design issue that tends to create cracks in the exhaust bridge.

Our reconstruction solves the issue in ~80% of cases; however, because it is a structural design flaw, we cannot guarantee long-term durability for the remaining ~20%.

Therefore, this is the best available option, but no durability guarantee can be provided since the defect is due to the manufacturer’s design.

For those who seek more power, we offer cylinder enlargement.

Once feasibility is confirmed, the de-coated cylinder bore is machined to the target size.

Feasibility depends on removable stock and residual structural rigidity.

It is the customer’s responsibility to ensure the upgrade’s feasibility and compatibility of other components.

The enlargement cost excludes re-chroming, which is necessary since the bore is machined on a de-coated cylinder.

The process also restores any head cover planes and O-ring grooves.

If a cylinder already has the ring, re-installation is required after re-chroming.