Usually this would mean you have the engine too lean or your carb is too open. Make sure your mixture screw is about 2mm below the top of the screw casing and if you take the airfilter out and look down into the carb make sure it is just 1-2 mm open.

If you have checked the settings then the other possibilities are

1. There is an air leak, or more likely:

2. The springs on the clutch shoe need tightening as they may not be holding the clutch shoe tight enough. You can adjust this by bending the clutch shoe spring but that would mean taking the clutch bell off.

If you need any help or want us to talk you through it feel free to call us on 01625 610031