The early Nineteen Seventies had been making an attempt instances at Harley-Davidson. The results of AMF’s takeover in 1969 had been trashing the corporate’s popularity and funds, and the flood of incoming Japanese requirements offered dependable low-cost options. To make issues worse, Harley’s grip on grime observe racing was in jeopardy after Brits had twisted the AMA’s arm for a single allowable displacement, regardless of the valve configuration. With the spine of Harley’s racing division threatened, it was a mad sprint to regain AMA supremacy from Triumph and BSA, ensuing within the all-conquering XR750 and a lesser-known pavement star referred to as the XRTT.
With scant sources to function on, Harley’s preliminary effort at an OHV 750 was primarily based on the 900 ci Iron-Head Sportster, with the engine de-stroked dramatically to fall with the allowable displacement. Whereas the previous KR operating gear was stable, the engines had been down on energy in comparison with their side-valve predecessors, and the iron heads and cylinders had a nasty popularity for overheating—the impetus for the nickname ‘waffle iron.’
Harley had the reply in hand, as designer Pieter Zylstra had devised a superior alloy high finish as early as 1969, however monetary issues drug out its improvement till 1972. Till then, the H-D devoted made do with the problematic Irons, with flat tracker Mert Lawill and California match racer Cal Rayborn reaching some notable successes.
When the alloy-head XR debuted for the 1972 season, the historical past of AMA racing would learn otherwise for many years to return. The XR proved dominant on the grime, taking 29 of 37 AMA Grand Nationwide Championships from 1972 to 2008, however earlier than the break up in 1985, a part of the championship included pavement as nicely.
Whilst you could simply mistake the XRTT for a very completely different bike, the underpinnings are virtually totally XR. The alloy head, OHV 750 offered easy revving as much as 8,200 rpm, good for 73 hp by way of a pair of 36 mm Mikuni carburetors and tuned exhaust.
A sculpted 5-gallon fiberglass gasoline tank with a leather-based chin pad and full bodywork mildew round your physique at full tuck, minimize simply away from the controls. The oil bag below the seat is aluminum, and a Smiths tachometer displays engine rotation.
Leaning on its European connections, Harley match the XR and XRTT with a Ceriani telescoping fork and a pair of Girling rear shocks. The place the XR had bear hubs, a large Fontana 4 main shoe drum was match up entrance, and a single caliper drum was used on the rear of the XRTT. Weighing proper round 320 kilos, the XRTT was slim and trim for a Harley, and was proper consistent with the BSA triples it usually confronted.
Someplace between 15 and 25 Harley XRTTs had been constructed, and riders like Mark Brelsford, Jay Springsteen and (most notably) Cal Rayborn put them to good use. Brelsford clinched the Grand Nationwide Championship in ’72, and Springsteen proved to be a dominant pressure within the Camel Professional Sequence within the late ’70s as nicely. By way of the Anglo-American Match races, there was maybe no extra inspiring sight than the thundering V-twin XRTTs amid a discipline of Triumphs, BSAs, Nortons and Suzukis.
Impeccably beauty and competitors historical past at a pivotal second in Harley’s story have been sort to the XRTT, and also you’d be hard-pressed to seek out one below $40,000. Lot R600.1 is a very beautiful 1972 Harley XRTT, the primary yr of alloy-head manufacturing, and its powerplant was rebuilt by marque knowledgeable Carl Patrick. Aside from the rubber, it seems proper for ’72, and it’s value noting that the four-shoe Fontana remains to be match, as many had been transformed later to discs.
This 1972 Harley XRTT is promoting at Mecum’s upcoming Las Vegas 2025 Motorbike Sale, the place it’s going to cross the block at no reserve. Mecum hasn’t detailed any identified competitors historical past on the bike, and the alleged engine rebuild is the one element we’re supplied with. Possibly it was a spare, who is aware of? No matter doubts we’ve got merely soften away wanting on the shiny end of this better-than-new restoration. If it sells, we’re betting the excessive $40k vary—and he or she’d be value it.
Supply: Mecum
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