If you find that the unit is backfiring, or kicking back on the recoil, it will be that the engine has settled in and the Valve clearances need adjusting.

Your engine is a system of moving parts, and moving parts wear. When you adjust a Valve, you’re not just adjusting the Valve itself but compensating for that wear, letting the Valve open and close as efficiently as possible.

Unbolt and remove the engine’s Rocker Cover (also known as Valve Cover). This is at the top of your Cylinder Head and covers your Rockers, Springs and the Stem of your Valves. If you need help identifying these parts, see the parts page for your unit here.

Although Rockers and Shafts add complexity, adjusting the Valves is fairly easy. You are adjusting the clearance between the Rockers and the top of the Valve Stems. Rotate the engine until the Piston is at the top of its compression stroke – also known as Top-Dead-Centre (TDC) – and both of the Valves are fully closed, the Springs are uncompressed and the system is at its loosest.

Insert a Feeler Gauge between the Valve Stem and the adjuster to check the gap. Too large a gap, you get clattery Valves, the linkage taking up the slack. Too small and you run the risk of Valve damage.

You need to adjust your Valves to the setting stated by the manufacturer in the manual. If you are unable to find these settings, we try to publish as many as we can on the “Valves” product descriptions on your model page.