Wow that is quite the list , I have a few questions
Is your Radiator leaking ?? , as its listed in the parts list
The list says the bike is not able to run , but you were riding it , so what are they claiming is the exact cause of it suddenly not running for them , when you were riding it ???
Did they say why the carb would need replacing as opposed to replacing possible clogged jets or jetting for the elevation ?? , the carb can be rebuilt without replacement , unless the carb body is damaged somehow , which i would find almost impossible to be the case
Most everything seems very unnecessary about this estimate , it is possible that the valves are going , and that could end up in the $500+ range , the stripped case bolt , is a bit of work , but not the need for a total rebuild along with replacing parts that have nothing to do with a stripped bolt , like the carb and radiator , so I am not sure what they are trying to do , i would tell them you ONLY want what is absolutely necessary to make it run properly with Jetting and fixing the case , and "checking" the valves , and ask how much that would cost (if the valves are out of adjustment , they will eventually need replacement , , and it would be a good idea to replace the piston and rings along with the valves but i am not saying that has to be done now , as it sounds like the bike is running ...or was running too good for the valves to be the issue) , if they still insist on doing the complete engine and replacing the carb , i would look elsewhere , or buy yourself a Service Manual from Honda and you can do the majority of the work yourself if you are somewhat mechanically inclined
As for the Chain , a 114 is for the stock 13/51 gearing , if your content with the current gearing for the riding your doing then a 114 along with new sprockets is correct , otherwise you will need to regear , which would possibly require a different length chain , depending on what sprocket sizes are used , I personally prefer Non O-Ring chains , as i feel that dusty or muddy conditions will ruin a O-Ring chain faster than a non O-Ring chain , i personally prefer DID or ER (both Gold chains) for the chain , for sprockets , i just go with cheaper Steel sprockets as they last much longer than Aluminum , the only advantage to Aluminum is for weight savings , if your not racing at the highest level , I feel its a unnecessary expense , especially for the shortened life span
I would ask them what Jet sizes they found in the carb , and match that to the list i posted earlier , if the jetting does not match what the list says for the elevation you are at , then change it to that and you should be good , you might need to replace the carb Slide Floating Valve Seal
https://www.crfsonly.com/catalog/produc ... ts_id/3687 , as they can cause bogging and idling issues
Again , from your original description , the bike did not sound like its in need of a complete engine rebuild and i would definitely not believe the carb needs replaced for any other reason than some part of the carb body is severely damaged , generally a carb "rebuild" which would consist of jets and O-Rings and seals , and possible Needle and Seat and a thorough cleaning , would be sufficient for most any issue you could encounter with the carb
Like i mentioned before , you could send your head here or even ship your complete engine and know that it would be repaired correctly , and nothing "unnecessary" would be added to the cost , you could contact Ken for a "estimate" and go from there , but either way , i am thinking you need to find somewhere else if your going to pay someone to do the work , as i believe there are things on that list that should not be there , and I am not sure you would be happy once all is said and done , or might be worse off than you are now , as I would guess from that list , that in the event something went wrong , or you had the same issues later on , they would not stand behind their work ....