GS400 left cylinder not firing until 1/4 throttle?

[brotus]

As the title says, my left cylinder is not firing at idle or until 1/4 throttle when it instantly comes online and runs great! This bike has the vacuum diaphragm operated slide in the carb which I am not very familiar with.
The symptoms lead me to think the pilot jet is clogged or the pilot air screw would need to be adjusted. I opened it up and cleaned all the jets, but there doesn't seem to be a pilot air screw on these carbs?! Am I missing something or do these type of carbs operate differently?

 

[hillsy]

The idle mixture screw may still be covered up with a brass plug (they were pre-set at the factory then covered so they could not be tampered with). You can drill a hole in the cover and use a self tapping screw to help pull it out. Be extremely careful not to drill too far past the plug and fubar the mixture screw.


Also, there should be a port in the carb bowl that a brass tube (from the carb body) goes into - make sure you clean the port and blow the tube out.


And make sure your valve clearances and the battery are good.