The last one I did took me about 6 hours with smoke breaks, coffee, and letting the dogs out. I didn’t remove the tank. Cut the pushrods and I only pulled the 2 left spark plugs. I also wrap the lower part of the frame and wiring with Saran Wrap to make sure no oil get on it. I also lay out all the tools I will need before I start so I’m not having to get off my stool to shuffle back and forth to the tool box.... being an aircraft mechanic, I don’t like fetching tools because it’s usually a long walk back to the hangar. Lol. If I was being paid to do it, I could shave an hour or so off it.
Edit: I will add, when I’m estimating a job, I try not to give a timeline that doesn’t allow for tool breakage, ect. If it was a 6-8 hour job, I wouldn’t mention 6 hours. I’d rather plan for the worse and deliver early when possible.