Reasons Why a Motorcycle Cannot Accelerate After Starting?
3 Answers
Motorcycle cannot accelerate after starting due to lean fuel mixture or poor crankshaft case sealing in two-stroke engines. Specific reasons are as follows: Lean Fuel Mixture: A lean air-fuel mixture causes insufficient gas pressure on the piston after ignition, prolongs combustion time, and leads to engine overheating. Symptoms of lean mixture include poor acceleration during operation, temporary improvement when manually adjusting the choke or pumping fuel, and recurrent acceleration weakness without enriching the mixture. Poor Crankshaft Case Sealing in Two-Stroke Engines: Air leaks from failed crankshaft oil seal on the generator side; sealing surface leakage at crankshaft case midline; leakage between crankshaft case and cylinder interface or incorrect piston installation orientation.
I just helped a friend with a similar issue on his Suzuki motorcycle a few days ago. The engine starts but the throttle doesn't respond, most commonly due to a clogged return port in the carburetor. Think about it—if fuel can't enter the combustion chamber, how can the engine have the power to respond to the throttle? The fuel line also needs checking. If the filter screen at the bottom of the fuel tank is clogged with rust, the fuel pump won't be able to draw fuel. A stuck needle valve in the carburetor float chamber can also cause the air-fuel mixture to become too lean. By the way, if the motorcycle has been sitting for a long time, the gasoline can degrade and form gummy deposits, completely blocking the internal fuel passages in the carburetor. If you're cleaning it yourself, remember to use carburetor cleaner to flush every small hole, especially the main jet and idle jet, then blow them clean with compressed air. Reassembling it should generally solve the problem.
Last time I rode my Kawasaki 400 in the mountains, I encountered a sticky throttle issue. The key is to check the throttle cable. If the inner cable at the handlebar connection lacks lubrication and grinds dry, the throttle grip will feel particularly heavy. Incorrect throttle cable routing angles can cause cable jamming when turning the handlebars to full lock. More troublesome is when the inner strands of the cable break - the outer sheath may look fine, but the steel wires inside become tangled and completely immovable. Throttle cable outer sheath displacement from its fixed position can also easily create sharp bends that restrict movement. For DIY repairs, I recommend removing the entire throttle cable, applying some chain oil at the handlebar end for lubrication, then working the inner cable back and forth until it moves smoothly. During reinstallation, ensure the cable follows natural curves and avoid sharp bends against the frame.
