BMW R50/2

Good day My R50/2 has a problem. It does not accept the gas. The carburettors are synchronized and the spark plugs are new. It also starts without problems. Super idle. I have already tried different nozzles in the carburettor and there was no improvement. I suspect that the ignition coil or the dynamo does not work anymore. How can I check them? Someone also told me that the swimmer eventuel has a crack and thus you don’t want the gas. anz, since the swimmer only makes sure that petrol comes into the float chamber. If someone has a tip and knows the problem with the gas acceptance. Thanks Urmel