Caterham starter. This ones odd!

[Rockets7]

Caterham 7 type 9 gearbox

Key in, switch on, fuel primes to carbs. With clutch up it turns over and starts sweet as a nut. With clutch down it has intermittent cranking speeds whilst trying to start from barely turning to normal speed. New battery. Starter stripped and refurbed. All earth leads checked, checked again and replaced. No immobiliser. Starter contacts are spotless. Battery contacts spotless. Positive cables are all without issue. What, why and any suggestions please?

[Rockets7]

Good points, little more detail... Has had a new engine in this year (upgrade). Problem remains, exactly the same. Clutch bearing was changed at time.

[Rockets7]

It's been the same for both engines. Clutch down, cranking is random speeds. Clutch up. Normal crank.

[Rockets7]

Arggggh further update. It now does it regardless of pedal position which leads me to think starter is weakening. Crank etc and flywheel are without issue but good points.