Several factors can contribute to a motorcycle shifting roughly between the 1st and 2nd gears. Here are some potential causes:
Clutch Adjustment: Improper clutch adjustment is a common reason for rough shifting. If the clutch cable is not adjusted correctly, it may not fully disengage the clutch plates when you pull in the clutch lever, resulting in difficulty shifting smoothly.
Clutch Wear: A worn-out or damaged clutch can cause rough shifting. When the clutch plates are worn, they may not engage or disengage smoothly, leading to difficulty shifting between gears.
Transmission Issues: Problems within the transmission itself, such as worn gear teeth, damaged synchronizers, or misaligned shift forks, can result in rough shifting. These issues can prevent the gears from engaging smoothly, causing a clunky or rough shift.
Lubrication: Insufficient or contaminated transmission oil can hinder smooth shifting. If the oil level is low or the oil is old and contaminated, it can cause increased friction and resistance during gear changes.
Rider Technique: In some cases, the rough shifting may be attributed to the rider's technique. Shifting too quickly or not fully engaging the clutch lever can cause the gears to grind or not engage properly.
Worn Chain or Sprockets: A worn chain or sprockets can affect the overall performance of the transmission. If the chain is stretched or the sprockets are worn, it can lead to inconsistent power transfer and result in rough shifting.
If you're experiencing rough shifting between the 1st and 2nd gears, it's advisable to have a qualified motorcycle mechanic inspect your bike. They can diagnose the specific cause of the issue and make the necessary adjustments or repairs to ensure smoother shifting.