Piston Clearances
We measure our clearances 0.400″ from the bottom of the skirt. What we have found works best is to find different pieces of paper in varying thickness, measure with a micrometer and write the thickness on the paper. If the piston falls through it’s got more clearance. If it stops in the bore it’s about right, and if it must be pushed through it needs more clearance to match the paper.
| Bore | Cast Iron Liner | Aluminium Liner | Ring End Gap Min. | Head | Valve – Intake | Valve – Exhaust |
|---|---|---|---|---|---|---|
| 89mm | 0.0015” – 0.002” | 0.016” | 0.055″ – 0.060″ | 0.060″ | 0.090″ | |
| 94mm | 0.0015” – 0.002” | 0.018″ | 0.060″ – 0.065″ | 0.060″ | 0.090″ | |
| 97mm | 0.0015” – 0.002” | 0.019” | 0.065″ – 0.070″ | 0.060″ | 0.090″ | |
| 98mm | 0.004” | 0.019” | 0.065″ – 0.070″ | 0.060″ | 0.090″ | |
| 99mm | 0.0045” | 0.020” | 0.065″ – 0.070″ | 0.060″ | 0.090″ | |
| 100mm | 0.005″ | 0.022” | 0.065″ – 0.070″ | 0.060″ | 0.090″ | |
| 102mm | 0.0015” – 0.002” | 0.022” | 0.065″ – 0.070″ | 0.060″ | 0.090″ | |
| 103.1mm | 0.0055” | 0.022” – 0.024” | 0.065″ – 0.070″ | 0.060″ | 0.090″ |
* NOTE: You can use pistons made for Aluminum liners in Cast Iron if you adjust clearances appropriately, this may result in premature wear and ring seal issues. It is NOT recommended to use pistons made for Cast Iron liners in Aluminum liners.