I agree with NC's mentioned upgrades, I did the same on my HT build. After spending way too much time on the forums planning out my build, I ended up getting initially:
- 66cc BGF RB80, in retrospect probably would have gone with the Pirate PK-80 for a few $ more just for peace of mind and not having the wider spaced intake studs
- SBP fuel valve: read too many horror stories about the stock ones leaking or not flowing enough, for $10, this is a nice sturdy petcock
- NGK B6HS spark plug: cheap and plugs are important, I never even screwed in the stock China plug
- AL exhaust gasket (which I still have not used) and extra head gasket. I figured I would need a new head gasket since the first thing I planned on doing with the motor before mounting was taking the head off to make sure there was no shrapnel in the cylinder. They say you can just re-use the original one, but I figured I was already there...
- SBP head stud kit and bolt kit: once again read so many horror stories about weak studs and the nightmare of getting snapped studs out, decided to replace them from the beginning. The allen head screws in the SBP kit look nice, too
From my local motorcycle shop:
- 3/16" fuel line, the thinner kind. People say the stock fuel line is junk, it felt that way to me, so I went ahead and got better fuel line. I went with 3/16" since I wanted it tiiiight. I think 1/4" would probably work too, but with 3/16" it was a struggle to get it on, but after it was on I found I did not need hose clamps
- Fuel filter. Mine had a good amount of black stuff in it pretty much immediately, I think paint chips...
During my install, before I even fired the motor one time, my spark plug boot disintegrated! When people say they are crap, they really are! Al.Fisherman here has an awesome replacement cap and wire, FWIW. I loved the Rajah cap he uses so much that I transferred it over to the plug wire that came on the coil with my Jaguar CDI.
As well, when trying to get my rag joint and sprocket centered on the rear tire, I gave up after about 7 hours of trying to get it right and ordered a sprocket adapter from Pirate Cycles. While there are many others here who get them to work, I think KC says he can get one on and centered in about 15 minutes, I could not.
So none of those upgrades are *needs*, but that is what I did for my install and would follow the same path again.