What are Camshaft & Valves?
The lobed shaft and spring-loaded valves that let fuel in and exhaust out at exactly the right moment.
Simplified animation — not to scale.
In plain English
The camshaft spins in time with the engine, its egg-shaped lobes pressing open the intake and exhaust valves at precisely the right instant before springs snap them shut again.
“Like a music box cylinder with pins plucking notes in sequence — except the 'notes' are valves opening in perfect time with the pistons.”
How it works
Driven by the timing chain or gears, the camshaft rotates at half engine speed. Each lobe pushes a valve open via a bucket, rocker or shim; a valve spring closes it again once the lobe rotates past. Getting this timing even slightly wrong causes rough running or, in a worst case, valve-to-piston contact.
Signs of trouble
- ⚠Ticking or tapping noise from the top of the engine
- ⚠Rough idle or misfiring
- ⚠Loss of power, especially at low revs
- ⚠Difficulty starting
£250–£900
Always get a written quote. Prices vary by bike, region, and parts brand.