Buell XBRR Development History / 2006 Daytona 200.

Author Erik Buell, September 2nd 2025.

As I remember, I was contacted by the AMA about their new class they were proposing. They very much wanted us to be in this series and had written a set of rules that their technical advisors felt might make parity between different engine types, much as they had done with 750 4-cylinder vs 1000 2 cylinders. They had decided that an air-cooled 2 valve pushrod twin could be 1300 cc. They also had written in the rules that any amount of welding/reconstruction would be allowed to crankcases and cylinder heads, etc.

I and some of the other engineers at Buell and Harley-Davidson sat down and determined that a large bore short stroke XB could make enough power to compete, although of course the crankshaft weight and inertia would be a problem for turning the bike. H-D/Buell marketing wanted to make a batch to sell to dealers to engage them in racing. To get a large bore in, the camshafts would need to move outboard, which could have been done by welding. But it would have been very messy and fraught with quality issues.

So, I called the AMA and said if we take a batch of crankcases, melt them down and re-cast them with the offset we would have done by cutting and welding we would have more durable motors, and as such would that not be better? There would be no performance difference from the cut and welded versions, just better quality. Of course, from my perspective it also would let me build some prototypes of production street engines with big bore and XB9 stroke to replace the struggling long stroke 1200 motor.

The AMA agreed that it met their ideas for the rules, so we started the project. Steve Anderson was the vehicle lead engineer, and I believe Gary Stippich was the powertrain lead. It was super rushed as the Daytona season opener was not far away!  The bodywork was made to get the best possible top speed as we knew long high-speed tracks would be the best opportunity for success, as the heavy crankshaft would be a disadvantage on tight tracks, even with the excellent chassis handling. I personally worked a number of all-nighters in the modelling shop making the bodywork design. I was coated with ground body filler and looking like a ghost in the mornings!

We built several prototypes and went to Texas late fall to test them, as I did not want to run Daytona without knowing the engines could finish. We ran two 200-mile tests without failure. The primary chains were destroyed by the end, but they finished. So, we knew there would be a few parts that would need regular service/replacement, but that is pretty normal on race engines. Most importantly the motors would finish Daytona.

The parts pipeline to get the bikes built in time for Daytona was kicked off. It was an insane scramble.

Unfortunately, Harley-Davidson powertrain engineering leadership decided they wanted to implement several new and different parts in the XBRR motors that they wanted to use in future XL/XB motors, and they also did not like one part we had chosen.

I was very upset and asked that they not change from what we had tested, since there were only 50 being built and they were specifically built for racing, not as production test beds. They said they would be dyno tested, and I said that dyno does not equate to track because the loads put into the motor are different. They blew me off. The parts included the lifters, the ignition and something in the transmission.

Four teams decided to run Daytona as I remember, several from Europe and a couple from the US.

In the Daytona 200 the bikes indeed looked quite competitive, especially Jeremy McWilliams who might have won, but every one of the XBRRs had an engine failure. In every case, these failures where those parts Harley-Davidson had changed after the test.

Harley-Davidson leadership berated us at Buell for this embarrassment. Not one time was there ever any acceptance that it was their own arrogance which caused the DNF's.

By far the highest output per cc air-cooled H-D based engine ever built and should have evolved into a super street XB motor. But was not to be. 

NCCR Sweden Buell XBRR page: here

Brian riding his Buell XBRR at the Donington CRMC event Saturday August 2nd 2025. Image credit: PJM Photography.

Saturday March 11th 2006. The Warr’s Buell race team make final checks to Jeremy McWilliams number one bike just minutes before the start of the Daytona 200.