Problem is one that I have experienced on my 150000 mile XJ750RK This is first signs of failure of carb diaphrams. The tinyest pin holes need magnifying lens to carefully study all four. I kept mine going for a time before finding good carb set. Proper replacement company exists. Diaphram can be carefully replaced with the right machine. Emergency repairs with very careful glueing of patch using thin rubber glove cut up,, and flexable glue.