Interactive
Tuning Tools & Calculators
Four free calculators for crankcase-scavenged 2-stroke mopeds. Set a target RPM or mix ratio, read the diagram, then confirm on the road — these are starting points, not dyno certificates.
How to use these tools
- Port timing — measure exhaust port height (or duration) first, then match pipe peak RPM to your real duration.
- Intake length — measure port → carb center → filter mouth along the air path; pick reed vs piston-port mode to match your engine.
- Expansion pipe — enter target RPM and port duration; use the profile as a layout guide before you cut metal.
- Oil mix — set ratio, choose US or metric units, enter gas or oil amount; the other side is solved for you.
After any port, pipe, or intake change, re-check jetting and plug color. Pair tools with the porting guide and platform pages under Classics.
Calculators
Port timing
Exhaust Port Timing
Duration, blowdown, and live cross-section diagram with engine presets.
Open tool →
Intake
Intake Length Tuning
Jennings ram, reed vs piston-port equations, scaled tract diagram.
Open tool →
Pipes
Expansion Chamber Designer
Graham Bell tuned length, cone angles, true-scale pipe profile.
Open tool →
Premix
2-Stroke Oil Mix
Interactive premix calculator and ratio chart by engine family.
Open tool →Pair with these guides
- Exhaust porting guide — before you raise a port, measure it
- Carb jetting — after any intake or pipe change
- Build paths — mild / mid / wild parts lists