Early Side Valve – 1932 Norton Big Four

In England, Vintage by Tim HuberLeave a Comment

Norton’s Big Four was the first motorcycle it produced with an engine that was developed and manufactured in-house. Production began in 1907 and would ultimately continue until 1954 when Norton would cease production on all of its side valve scoots. Various changes in displacement and hardware would occur over the years – continuous production would go on despite the Great Depression and two World Wars. The Big Four supposedly gets it name from the 4 tax horsepower that it initially produced (a rating from the early-1900’s derived from a mathematical formula based on cylinder dimensions rather than actual engine power). If measured in brake horsepower, the Big Four would be the “Big Fourteen”.

The Big Four was introduced as a 633 cc side valve model and at the time was reportedly the largest and most powerful side valve in existence. For its day, the Norton produced a staggering amount of torque and consequently made for an ideal sidecar tug. The actual “Big Four” denomination first appeared on the “Model 1” in 1907. Later on, the official denomination of the Big 4 was “Model 7” – excluding bikes with a sprung rear frame which were known as the “Model 8” – but the “Big 4” moniker stuck, even after the displacement dropped to 596cc in 1948.

The Big Four would also become a go-to model for military use thanks to its reliability and sidecar-friendly engine that allowed it to be equipped with everything from munitions transport rigs to Thompsons, Bren light machine guns, and three-inch mortar bombs. In the first World War, the Russian army would place a large order of Big Fours from Norton, as did the British Army which reportedly ordered some 100,000 units in WW2, several thousand of which were sidecar rigs. The 633cc Big Four was a personal favorite of James Norton who toured around Africa aboard one of the 633cc side valve singles in the 1920’s, thinking getting out of the smoggy industrial city of Birmingham and spending time breathing in fresh air would help his worsening health.

Norton was a successful marque in racing from very early on, nabbing one of the first ever TT wins with a Norton powered by a French engine. The British manufacturer would go on to dominate in competition, especially in the 1930’s. Norton’s Manx was responsible for winning races – a key element of the company’s marketing strategy – but the Big Four was responsible for paying the bills, and it did its job well.

Powering this Big Four example is an air-cooled, 633cc side valve single that reportedly makes 14.5 hp at 4,000 rpm and is married to a four-speed transmission with chain final drive. The 305 lb (dry) Big Four was capable of almost 70 mph, though its drum brakes reportedly were pretty underwhelming even upon its release. The suspension on the Big Four – aka Norton Model 1 – was comprised of girder units in front and a hard tail rear end with a sprung saddle.

This example is a 1932 Norton Big Four with the original 633cc side valve engine. Examples are extremely rare and therefor pretty valuable. This particular Big Four has been fully restored and is said to be in pristine mechanical and cosmetic condition. Though the ad includes some decent photos, the seller also included a link to a YouTube video they made of the bike being ridden:

It’s a beautiful example of a pre-WW2 British motorcycle and it has a lot of character; that exhaust alone is pretty snazzy, but the hand-shift and girder forks really bring it home. You can find this 1932 Norton Big Four for sale here on Craigslist in St. Lucie West, Florida with a price of $19,300.