There could be several reasons why a motorcycle stalls or dies when selecting the first gear. Here are some possible causes:
Clutch engagement: One common reason is improper clutch engagement. When shifting into first gear, it is essential to fully disengage the clutch lever to allow for a smooth transition. If the clutch is not fully released, the motorcycle may stall because the clutch plates are still engaged, causing the engine to struggle against the resistance of the transmission.
Idle speed: If the idle speed is set too low, the engine may not generate enough power to keep running when you engage the first gear. A low idle speed can result from misadjusted idle screw or a problem with the idle control system. Adjusting the idle speed to the manufacturer's specifications can help prevent stalling.
Fuel or air delivery issues: A motorcycle may stall if there are problems with fuel or air delivery. Insufficient fuel flow, clogged fuel lines or filters, a malfunctioning fuel pump, or a dirty carburetor can lead to a lean fuel mixture, causing the engine to stall. Similarly, a restricted air intake, such as a dirty air filter, can disrupt the air-fuel ratio and cause stalling.
Electrical issues: Faulty electrical components can also lead to stalling when selecting the first gear. For example, a malfunctioning sidestand switch or a faulty neutral switch can interrupt the ignition circuit and cause the engine to cut off when shifting into gear. Additionally, issues with the ignition system, such as a weak spark or a failing ignition coil, can contribute to stalling.
Engine problems: Certain engine issues, such as low compression, valve problems, or a malfunctioning fuel injector, can affect the engine's ability to maintain idle or handle the load when engaging the first gear. These issues may cause the engine to stall or run poorly.
If your motorcycle consistently stalls when selecting the first gear, it is advisable to have it inspected and diagnosed by a qualified mechanic. They will be able to identify the specific cause of the stalling issue and perform the necessary repairs or adjustments to restore proper operation.