A motor will die when put in gear if there is a major vacuum leak. This causes an excessive amount of air to enter the engine and lean out the fuel mixture.
outboard motor will start and idle, but dies out under load
check that choke is operating correctly
what causes a boat motor 40 hp to stall when it is put in gear
If a 1988 Chevy Cheyenne dies when it is put into gear, check the fuel pump. If the fuel pump is not getting adequate fuel, it will cause the car to die.
If the 1984 Honda Accord engine dies when put in gear then it could be due to some faulty wiring.
Push in the clutch and give it more gas.
check the side stand switch , this cuts out the engine if it (the side stand) is down when you put the bike in gear .
check gear shift linkage if transmission is bad
Fuel injection or fuel contaminated?
if this is a automatic truck change the distributor pick up had same problem on 1989 b 2200
check motor mounts