Harley-Davidson XA to Wheatcroft

October 2015

Military motorcycle | Indian 841 | Willys Jeep |

The Wheatcroft Military Collection at Donington Park, Leicestershire, has acquired an XA Harley-Davidson—or, more accurately, has acquired another XA. Apparently, the museum already has five of these experimental HDs on display, and now it has six.

So what was the XA? Well, the "X" stands for "experimental". And the "A" is for "army". The 23hp, 738cc bike (nominally a 750) was developed during the early part of WW2 following the capture and examination of a sidevalve/flathead BMW R71 (and not a BMW R75 OHV twin as is often stated). The US government was suitably impressed with the sophistication of German motorcycle engineering, particularly the fact that the R71 was equipped with a shaft drive making the bike well-suited to hostile natural environments. In particular, it was noted that the flat-twin layout kept the cylinders significantly cooler than a conventional V-twin, thereby reducing wear, extending the maintenance cycles, and prolonging oil-life. The XA, incidentally, carried a throttle on the left and a clutch lever on the right.

The XA bore and stroke are both 3.125-inches. The compression ratio is 5.7:1. The carburettors are Linkert. The weight was around 520lbs, all up. The wheelbase is 58.7 inches. The frame is a dual cradle. The front fork is an extended WLA unit. A Thompson sub-machine gun (aka Tommy Gun or Trench Broom) in a scabbard was standard issue.

A government contract was subsequently issued for 1,000 XA motorcycles. And to make it interesting, Indian, which was also vying for a contract, developed the (almost) equally rare Model 841.

The Indian 841 was more radical. It employed a totally new sidevalve V-twin engine, rotated 90-degrees and coupled to a four speed gearbox with a shaft drive to the rear wheel. Moto Guzzi later made that layout its own. But Indian pioneered the idea around 1941. A sprung hub was fitted at the rear. The engine output was a claimed 25hp (two more than the XA).

▲ Indian 841 V-twin flathead. Radical, but an evolutionary dead end.

Shifting was by foot with a hand clutch lever. The front fork was a new girder design. Tapered oval tubing was used to keep the strength up and the weight down.

The Harley-Davidson XA was also a sidevalve with a four speed gearbox and a shaft drive. But with its horizontally-opposed boxer engine, the XA was a more faithful/convincing/rip-off BMW R71 clone. Around 1,011 units are claimed by many sources to have been built (it's a number that perhaps needs further investigation).

Finally, the US government opted instead for the Willys Jeep for general purpose use and reconnaissance, and the military purchased the 740cc WLA Harley-Davidson for despatch and military policing work.

So why abandon the XA? Well, the government felt that the Jeep was more practical/versatile and was more cost-effective than the XA. Meanwhile, the Harley-Davidson WLA was also considered more cost-effective and was better understood, technically speaking. And maybe there was some national pride in the mix, specifically in the implied notion that German bikes were better than American bikes. Joseph Goebbels, the Nazi information minister, might have wrung a lot of useful propaganda from that.

The XA never saw active service. Neither did the Indian 841. But the US military did purchase the (more conventional) Indian 741B.

It's not clear how many XAs are left in the wild, but of the original "1,000" bikes, we hear that just 12 have survived (also a questionable figure). The Wheatcroft XAs are presented in various guises; one as an outfit, and two with "disc" wheels. The latest incumbent looks like a fairly standard machine. But exactly why the museum wants six XAs on display is unknown.

Throughout the year you can visit the Donington Park Grand Prix Collection, which incorporates the Wheatcroft Military Collection. Adults will pay £10. It's £4 for children aged 16 and under.

www.donington-park.co.uk

— Big End