Here is the Operator's Manual:
http://bsintek.basco.com/BriggsDocumentDisplay/flmtxLX-nfBhU7y.pdfHere is the Illustrated Parts List:
http://bsintek.basco.com/BriggsDocumentDisplay/BInnCFXBnfBhU7y.pdfBest fit for the symptoms is very lean mixture. As I read what you've said, you have trouble starting it unless you squirt fuel in, but once started it runs perfectly. In other words, you have a problem with the cold enrichment system.
At this point I don't know whether you have a primer, a manual choke, or an automatic choke. As I read the manual, they seem to have made versions of the engine with each of those three. Whichever you have, it appears not to be working as you are calling on it to work. So, next step is we need you to tell us just what you have there. I already have a strange sinking feeling that you may have the ReadyStart automatic choke - I think that is the most common cold enrichment system for the 120000 series vertical crankshaft engines. That system is capable of working acceptably, but is often misunderstood and mishandled by tenants. In order to comply with emissions requirements, it only chokes the engine when it is completely cold - after being out of use overnight for example. Once the engine has run for even a very short time - perhaps a few seconds - you do not get any choke application at all on restarts. Normally a mower is run until you need to empty the catcher, and by that time the engine is properly warm and does not require choke. However experimentally-minded tenants may stop it before it is fully warmed up, and then they are just out of luck as far as being able to restart it is concernced.
If you have a ReadyStart system, and you confirm that your problem is that the tenant can't restart it when it is half-warm, you seem to have a choice between retraining the tenant, or fitting a similar carburetor with a manual choke or primer bulb.
