What are the symptoms of carbon buildup in motorcycles?
3 Answers
Motorcycle carbon buildup manifests in the following ways: engine shaking, difficulty in cold starts, sensor signal failure and three-way catalytic converter malfunction (i.e., exhaust system blockage), unstable idle speed, intake backfire, exhaust popping, decreased vehicle horsepower, etc. Another phenomenon is that when the hot engine shuts down, it cannot stop working immediately, leading to increased fuel consumption and excessive emissions. Carbon buildup includes two concepts: 1. Engine carbon buildup: A coking-like substance produced by unsaturated olefins and colloids in fuel under high temperatures during engine operation. 2. Carbon buildup in EDM (Electrical Discharge Machining): Carbon buildup in EDM is something that should be avoided as much as possible, especially in precision mold processing where it can have fatal effects.
When I first bought my used motorcycle, I immediately ran into carbon buildup issues. The most obvious symptom was struggling on slopes - even with the throttle wide open, it felt sluggish. Fuel consumption was also 20% higher than other same-model bikes, with a full tank barely lasting 200km. Cold starts required 5-6 kicks to fire up, and the exhaust pipe would spit out black residue. The mechanic showed me the cylinder head after disassembly - the piston crown was covered with coal-like deposits. He explained these were clogging the valve clearances and causing incomplete combustion. His advice: stop using cheap gas from small refineries and take highway runs every 5,000km to clear carbon deposits. Now the bike runs much more powerfully.
A seasoned mechanic who has repaired hundreds of motorcycles tells you: Carbon deposits are most deadly when causing cold start difficulties. This morning, a customer pushed his bike into the shop, complaining about having to crank the starter over a dozen times with the clutch pulled in before it would start, and experiencing backfires while riding. Upon removing the spark plug, the electrodes were found blackened, and the intake manifold was greasy. These carbon deposits are like slathering cement on the engine, not only affecting cylinder compression but also causing the oxygen sensor to misread and the ECU to misfire the fuel injection. Here's a little tip: For carburetor models, you can lean out the air-fuel mixture; for fuel-injected bikes, regular use of Red Line additive is far cheaper than tearing down the engine.
