From what you have said it seems that you may have more than 1 problem
The brake cleaner slowing the engine when sprayed on the front manifold seal would tend to indicate that the seal is leaking
The no spray from the accelerator pump would indicate that either the pump channels are blocked or the diaphragm is leaking
There may be additional problems not yet identified
Modern fuels are not kind to plastic and rubber components in a carb if fuel is left for a long period in the carb without use it can evaporate and leave varnish which will block or partially block some of the channels in the carb
There are 2 possible solutions 1st is to do a complete rebuild of the carb using a full rebuild kit which should replace all the rubber parts and seals
Or replace the carb
Brian
The brake cleaner slowing the engine when sprayed on the front manifold seal would tend to indicate that the seal is leaking
The no spray from the accelerator pump would indicate that either the pump channels are blocked or the diaphragm is leaking
There may be additional problems not yet identified
Modern fuels are not kind to plastic and rubber components in a carb if fuel is left for a long period in the carb without use it can evaporate and leave varnish which will block or partially block some of the channels in the carb
There are 2 possible solutions 1st is to do a complete rebuild of the carb using a full rebuild kit which should replace all the rubber parts and seals
Or replace the carb
Brian