Bog (Throttle Hesitation)

A bog is when the engine hesitates, stumbles or briefly loses power as you open the throttle, instead of picking up cleanly. Off-road it can stall the bike on a jump face or in a corner exit, so it matters more than it might seem.

The usual cause is a wrong fuel mixture at the moment of throttle opening. On carburettor bikes check the pilot jet and air screw, needle position, float level and the accelerator pump squirt and timing. A dirty air filter, a blocked carburettor vent, water in the fuel or an air leak in the intake can also cause it. On fuel-injected bikes, look at sensors, injector cleanliness and fuel pressure.

A bog that appears after fitting an aftermarket exhaust or filter usually means the jetting or fuel map needs adjusting. Note whether it happens hot or cold and at which throttle position.