x2 vote on crud inside. I got a "never ran" 1406 off Craigslist (good deal anyway) and I bolted it it, it lead extremely bad, in fact people advised me to throw it away cause it was a "firebomb" lol. (this was the internal leaking after killing the engine
https://www.youtube.com/watch?v=5tbfjPNZLAw) It leaked a lot outside too.
All of this was because of dirt that had been able to fall inside of everything. I just took it apart and blew out all of the lines and re-adjusted the floats. Ran like a champ afterwords until the engine took a dump.