It's hard to not laugh when "Harley" and "road race engine" are used in the same sentence. Eric Buell was the only one who came close to being competitive, and as soon as he made the podium, he went out of business. After the Japanese entered the racing scene, Harley couldn't keep up, and stopped trying. Unfortunately, the golden age of motorcycle racing is gone. Today's racing is good, but just not the same.
In terms of racing, the two strokes killed everyone, not just Harley. They were unreliable, handled like flung feces, but they were ungodly fast when they were on and the brits and Harley couldn't touch them. Rayborn died in December 1973 and the first tz700s hit the circuit in the 1974 racing season, the combination of those two events was the death knell for HD and everything else 4 stroke at top level racing (at least until the early 2000s).
In road race classes that favored 4 stroke twins (like BOTT), the XR was competitive well into the 1980's in privateer hands with bikes like lucifer's hammer and TO's xr909 holding their own against ducati, guzzi, and BMW.
But racing isn't road bikes, and HD had a competitive performance product in the sportster until about 1976, when the rest of the field caught up to the KZ900 in terms of speed and left things like the sportster and what dregs remains of the British motorcycle industry behind. But it wasn't performance that put those bikes in the ground, it was reliability. HD had many internal culture problems before AMF bought them, and while AMF takes a lot of blame for poor product quality the AMF bikes were actually better than the ones that came just before. Engineering, R&D, production, and racing all ran separately and none of them communicated with each other, and were antagonistic about it. There are many many many stories about how production would source a part inferior to engineerings specs and use it without consulting engineering or engineering overwriting parameters without regard to ease of production and the result was a brand new bike that didn't run and had a recall on it before the customer picked it up and cost too much to build in the first place.
I don't generally like Harley's, and I despise (yet respect) Harley "lifestyle" marketing, but I have nothing but awe for Dick O'Brien and the Harley racing department from the 50's to the 90's. He took a spit sandwich of a department that had been gutted by its former leadership (literally the former racing director took everything when he left - or so the legend goes) and had only one competitive but antique racing design, the KR flathead, and made a force to be reckoned with on road courses out of guys like Carol Reiswebber and Cal Rayborn.
In terms of Erik Buell and podiums, EB was NEVER head of the racing department nor a factory rider for HD. He was an engineer first (worked on the nova v4 project) and then came back as the head of Buell under HD, most everything else he did he did as a privateer. After Dick left HD in the 80's (he still consulted after) the HD racing department didn't get their footing again till the 1990's under Steve Scheibe and the VR1000 racing project. If there were any HD podiums to be had the thanks goes to Steve and not Erik whose role at HD was to sell performance road bikes.
