There could be several reasons why your motorcycle stalls or quits when you put it in gear, even after having the carburetors professionally cleaned. Here are a few possibilities to consider:
Clutch Issues: One common cause of stalling when shifting into gear is a problem with the clutch. If the clutch isn't engaging or disengaging properly, it can prevent the bike from moving forward smoothly and cause it to stall. The clutch may require adjustment, or there could be a problem with the clutch plates, springs, or cable.
Idle Speed: If the idle speed is set too low, the engine may not generate enough power to prevent stalling when you engage the clutch and put the bike in gear. Check if the idle speed is within the manufacturer's recommended range, and adjust it accordingly if necessary.
Vacuum Leaks: Vacuum leaks in the intake system can disrupt the air-fuel mixture and cause the engine to stall when the bike is put in gear. Even after carburetor cleaning, it's possible that there is still a vacuum leak present. Inspect the intake manifold, carburetor boots, and vacuum lines for any cracks, loose connections, or damaged gaskets.
Fuel Delivery: A problem with the fuel delivery system can also lead to stalling when shifting into gear. Check if the fuel filter is clogged or if there are any restrictions in the fuel lines. Ensure that the fuel petcock is functioning correctly and providing an adequate fuel supply to the carburetors.
Electrical Issues: Faulty ignition components, such as the spark plugs, ignition coils, or wiring connections, can cause the engine to stall when you engage the clutch and put the bike in gear. Inspect these components and ensure they are in good condition.
It's worth mentioning that diagnosing the exact cause of the issue may require a thorough inspection by a qualified motorcycle mechanic. They can perform further tests and checks to pinpoint the underlying problem. Providing them with specific details about when the issue occurs (e.g., only when the engine is cold, consistently in a specific gear, etc.) can assist in the diagnosis.