MasterTune Moto Suite
PW50
Cobra (coming soon)
CRF50 (coming soon)
KTM Mini (coming soon)
Piston Clearance & Ring Gap Calculator
Enter your piston diameter to calculate your ideal
ring end gap
using Gordon Jennings’ tuning rule: 0.004" per inch of piston diameter. Applies to cast rings on a steel bore.
🧩 Select Piston Size
40.00mm Stock
40.25mm OS Level 1
40.50mm OS Level 2
40.080mm Wiseco
44mm Chinese (extra clearance)
44mm Tri-Zinger
44mm PAX
44mm Factory51
🏁 Application Type
Rec / Trail
Race
Sand / Dunes
High-RPM Mod Build
Your Measured Ring Gap (inches)
CALCULATE
Final Bore Diameter:
40.030 mm
