Here's a breakdown of what's likely happening and steps to diagnose and fix the issue:
The Problem:
* Fuel Delivery Issue: The engine is getting enough fuel at low throttle openings, but it's not getting enough when you open the throttle more. This suggests a problem with fuel flow, either in the fuel system or with how the carbs are responding to throttle position.
Why Spraying Fuel Helps:
* Bypass: Spraying fuel directly into the intake bypasses the carbs and fuel delivery system, showing that the engine is capable of running with sufficient fuel.
Potential Causes and Solutions:
1. Clogged Fuel Lines/Filter:
* Check: Examine the fuel lines for any blockages or kinks. Inspect and clean or replace the fuel filter.
* Solution: Replace any damaged or clogged lines and filter.
2. Carb Problems:
* Float Level: The float level in the carburetors might be set too low, preventing the carbs from delivering enough fuel at higher throttle openings.
* Jets: The main jets might be clogged or too small.
* Diaphragm: The accelerator pump diaphragm might be torn or not functioning properly.
* Check: Remove the carbs, carefully disassemble them, clean them thoroughly, and inspect all parts for wear or damage.
* Solution: Adjust the float level according to specifications. Clean or replace the main jets. Replace the accelerator pump diaphragm if needed.
3. Fuel Pump Issues:
* Check: Inspect the fuel pump for any signs of damage or malfunction. Test its output pressure.
* Solution: Replace the fuel pump if necessary.
4. Air Leaks:
* Check: Inspect the intake manifold, carb boots, and airbox for any leaks that could be drawing in unmetered air, making the fuel mixture too lean.
* Solution: Repair or replace any leaking components.
Troubleshooting Steps:
1. Start Simple: Start by checking the fuel lines, filter, and fuel pump as these are the easiest to inspect.
2. Carb Cleaning: Clean the carbs thoroughly, even if you just did it recently. There might be stubborn debris you missed.
3. Float Level: Check and adjust the float levels. Make sure they are set to the manufacturer's specifications.
4. Pressure Check: Use a fuel pressure tester to check the fuel pump's output pressure.
5. Leak Check: Use carb cleaner or propane to check for air leaks in the intake system.
Additional Tips:
* Carb Synchronization: If the carbs have been cleaned and the float levels are correct, consider having the carbs synchronized. This ensures that all cylinders are receiving the same amount of fuel.
* Troubleshooting Guide: Refer to a motorcycle service manual specific to your 1983 GS1100 for detailed instructions and specifications.
* Professional Help: If you are not comfortable troubleshooting motorcycle fuel systems, it's best to take it to a qualified mechanic for diagnosis and repair.
By following these steps and understanding the potential causes, you should be able to identify and resolve the fuel delivery problem causing your GS1100 to bog down.
