First, try to fix it with paint.
The kit chrome would not strip even with bleach, so it was sanded away and the surface rebuilt from the primer up. Heat colors were layered over bright silver to move the finish closer to the real titanium exhaust.
299 MODEL WORKS / JOURNAL 04MAIN ARTICLE / NOV 2025
NINJA ZX-10R / CAD / 3D PRINT / PAINT
Building a Custom Ninja ZX-10R Exhaust.
Repainting the kit exhaust was not enough to capture the real bike’s shape and heat discoloration. Using reference photos, real-bike measurements, and official images, I redesigned the exhaust in CAD and refined it through roughly ten prototypes and paint tests for a 1/9 model.
SCALE1/9
TEST PRINTS~10
DESIGNCAD
FINISHHEAT STAINING
01 / START
Rebuild the kit exhaust.
WHY REBUILDThen rebuild the shape.
The exhaust was modeled in CAD from photos and measurements supplied by the owner. Model-scale thickness, paint build, and sanding access were considered, and the bands and brackets were separated into individual parts.
02 / PROCESS
Solve the shape and the finish separately.
5 STEPSOrganize the references.
Compare real-bike photos, measurements, and official images to identify the key dimensions and visual features.
Design in CAD.
Build the geometry so the measurements remain consistent while also checking how the shape reads at model scale.
Repeat prototypes.
Check printing, test fit, sanding access, and paint thickness through roughly ten prototype iterations.
Separate the parts.
Make the front and rear bands and bracket separate pieces so surface preparation and painting remain practical.
Paint the heat staining.
Spray yellow, red, blue, and transparent clear layers in sequence to build the gradient without losing gloss.
03 / FINDINGS
What the tests revealed.
MODEL MAKINGA metallic finishdepends on the base.
The gloss black and clear base had to be made very smooth, then the bright metallic layer built up gradually in small amounts.
The thinner the color,the easier it is to go grainy.
The narrower the heat-color boundary was sprayed, the more easily the surface lost gloss. Alternating color and transparent clear helped preserve the finish.
The paint processbecomes a design constraint.
With a one-piece print, paint built up too heavily around the bands. Considering sanding and painting access, separating the parts was the more practical design.
04 / LINKS
Read the related posts.
MAIN / RELATEDMAIN ARTICLE
Custom exhaust build.
The main article covering CAD design, prototypes, part separation, metallic finish, and heat-stain painting.
READ BUILD LOG [JP] ↗BEFOREPainting the kit part.
An earlier article where the stubborn chrome was sanded off and heat staining was tested on the kit exhaust.
READ BUILD LOG [JP] ↗GALLERYSee the finished result.
Finished photos show the custom exhaust installed on the bike, including the outlet mesh and heat discoloration.
VIEW GALLERY [JP] ↗Making the shape is not the end.
A model part is not finished simply because it prints to the intended dimensions. It also has to be sandable, paintable, and installable. This exhaust became a practical example of connecting CAD and 3D printing to real scale-model work.