First - you need to give us an approximate idea of where you are - Samurais are not the same in every corner of the world - and we have no idea what a "stock 87 tin top" in your corner or the world is the same as it is in our corner of the world.
Next - you may need to either, depending on what is available in your corner of the world, learn the basics of auto mechanics so you can do the preliminary troubleshooting, or get some sort of roadside assistance package where someone will come out and do it for you. Intermittent problems can be a pain to locate, and can't see the symptoms, it's going to take him a long time to figure it out, and for him, time is money - your money I might add.
Basic troubleshooting - like checking for a spark at the coil or a plug - or - spraying starter fluid into the intake whilst cranking which helps determine if it's a fuel or spark related problem.
I also want to mention, in passing, that many years ago, I had a very similar problem with a motor cycle - it would just up & die on me, as if it had run out of fuel - I eventually tracked it down to a tiny seed (from a plant) inside the carburetor - it would move around and occasionally block the main jet cutting the fuel supply to the engine - I had to completely strip the carb to find it.
You have not mentioned cleaning the carb, and putting a filter before it won't remove anything that's already in the carb ...