Cutaway engine bonanza at Bonhams

▲ Edward Turner, Triumph's one-time General Manager and designer of the 5T Speed Twin, expended a lot of time and creative energy draughting the Ariel Square Four engine (immediately above). With its radical contra-rotating twin-crank bottom end, it first appeared in 1928. Numerous variants have since rolled down the years. The 1000cc Mk2 "Squariel" shown here (Lot 239) was prepared for the 1952 Earl's Court Motorcycle Show. It went to the US soon after, and we'd like it back if anyone in Britain still has any money.

We're probably incorrigible Philistines here at Sump, because given the choice of having a few Rodin sculptures loitering on plinths around the mansion, or having a cluster of cutaway motorcycle engines collecting house dust, the Rodins would end up in the recycling bin, or beside the bird table.

Ditto for anything by Moore, Hepworth or even Michelangelo. Artworks by these celebrated sculptors are all nothing but driveway-gravel-in-the-making when compared to, say, the 1953 Ariel Square Four lump immediately above, or the 1957 BSA A10 engine immediately below.

And yes, we're deeply ashamed to make that admission, but we suspect a fair number of you guys and girls are harbouring dirty little cutaway secrets of your own.

Auction house Bonhams is certainly counting on that because, come 8th January 2015, the firm is putting a bunch of classic British motorcycle engines up for sale, and all of them are artistically hacked about to reveal their gory innards. Lovely.

▲ Lot 241. We've seen A10 engines with bigger holes in 'em than this, and some of 'em were still running. But this motor is as dead as dead can be. Still, there's nothing wrong here that a welding torch and a tube of Solvol Autosol won't fix. But is it art? Or vandalism? Or both? Or neither? And do we care?

Here are some of the cutaway lots on offer:

Lot 239: 1953 Ariel Mk.II Square Four

Estimate: $ 25,000 - $35,000 (£16,000 - £23,000).

UPDATE: Sold for $28,750 (£18,947) including buyers premium

Lot 240: 1956 BSA DBD Gold Star.

Estimate: $20,000 - $30,000 (£13,000 - £19,000)

UPDATE: This lot didn't sell

Lot 241: 1957 BSA A10 Road Rocket
Estimate: $15,000 - $20,000 (£9,700 - £13,000)

UPDATE: This lot didn't sell

Lot 242: 1959 Matchless G80 Typhoon
Estimate: $15,000 - $20,000 (£9,700 - £13,000)

UPDATE: This lot didn't sell

Lot 244: 1956 BSA B34 Gold Star Clubmans (complete motorcycle)
Estimate: $250,000 - $350,000 (£160,000 - £230,000)

UPDATE: This lot didn't sell

Lot 245: 1961 Norton 88 SS Dominator
Estimate: $15,000 - $20,000 (£9,700 - £13,000)

UPDATE: This lot didn't sell

Lot 246: circa 1949 Sunbeam S7/S8.

Estimate: $15,000 - $20,000 (£9,700 - £13,000)

UPDATE: This lot sold for $23,000 (£15,158) including buyers premium

Lot 247: 1964 BSA Lightning Rocket (complete motorcycle)
Estimate: $40,000 - $60,000 (£26,000 - £39,000)

UPDATE: This lot didn't sell

Lot 248: circa1963 Norton Electra 400
Estimate: $10,000 - $15,000 (£6,400 - £9,700)

UPDATE: This lot didn't sell

Lot 249: circa 1952 Triumph 6T
Estimate: $15,000 - $20,000 (£9,700 - £13,000)

UPDATE: This lot sold for $10,350 (£6,821) including buyers premium

▲ Lot 244. This considerably lightened 1956 BSA Gold Star is going to take a weight off someone's pocket on January 8th 2015—but if anyone actually pays the quarter-of-a-million dollar lower estimate, some will think the buyer needs sectioning too (under the Mental Health Act). Meanwhile, we're not even going to mention the poor bastards starving to death in Africa and elsewhere...

But take note that two of these lots are complete motorcycles rather than "mere" engines. The first is Lot 244, a 1956 BSA B34 Gold Star. This bike, we hear, graced the BSA stand at that year's Earl's Court Motorcycle Show. But it was actually built in 1953.

However, three years later BSA decided to upgrade it. And not content to merely section it, the firm motorised various components to illustrate the engine operation (pistons, crank, valves, pushrods, clutch etc). They also jury-rigged a pair of cams under the wheels to get them spinning and bouncing up and down with the suspension. And they made as much hoopla about it as possible.

Immediately after the Earl's Court Show, it's unclear exactly where the display model went. But by the mid-1980s it turned up in New Zealand in the hands of long-established racer Rod Coleman. He flogged it to Bob Schanz of DomiRacer and it was relocated to Cincinnatti, Ohio. The display model was later loaned to the AMA Museum (also in Ohio).

US Collector Herb Harris acquired it in 1999 and reworked it a little, and it now runs at 9 rpm, which is half the original speed. Bonhams is looking at the bright side of $250,000 (£160,000), and feels it could go as high as $350,000 (£230,000).

If this was comedy week, we'd say that Bonhams is having a laugh. But this is stone cold December 2014 (going on January 2015), so maybe Bonhams knows something that we don't.

Meanwhile, Lot 247 (immediately above) is another complete motorcycle, this being a 1964 BSA Lightning Rocket. The estimate is a fairly hefty $40,000 - $60,000 (£26,000 - £39,000). There's a considerably less illustrious back-story with this bike. But it's still a pretty cool piece of kit (or should that be "a cool piece of kitch"?), and we still prefer it to anything by Rodin or Michelangelo. But who the hell are we to judge anything?

▲ Lot 246. A circa-1949 Sunbeam S7/S8 cutaway engine. This unit, as we understand it, was one of two S7/S8 engines sectioned by Sunbeam for display at the London Earl's Court Motorcycle Show. There's no specific information on what year, so we're assuming 1949. Regardless the model was acquired by US collector, Herb Harris, who restored it to its present condition. The engine is one of numerous cutaway display units to be auctioned by Bonhams at its Las Vegas Sale on 8th January 2015, just a few weeks away. Bonhams is estimating $15,000 - $20,000 (£9,700 - £13,000). A little optimistic? We can't decide, so we're just watching. But when it comes to pretty engines, we think this 500cc in-line, air-cooled, shaft-drive twin is up there with the very best of 'em. Shame to wreck one simply for people to gawp at. But this is (arguably) motorcycle art, and a little relaxed gawping never did us much harm.

▲ The 650cc Triumph 6T air-cooled parallel twin. Is this the greatest of all British classic bike engines? Maybe. It's got the simplicity of the 500cc 5T, has a little extra grunt to crack the magic ton, is easy to fix, easy to live with, easy on the eye, and breaks effortlessly through the class barrier (not that we officially have that anymore in the UK). It's an "everyman" engine, just as Triumph intended.

▲ .... then again, the 500cc BSA B34 air-cooled single (immediately above, Lot 240), takes some beating in terms of both looks and performance. If we had to be killed by an engine falling on us from a great height, this might well be the one we'd pick.

▲ 1961 500cc Norton Dominator 88. The Dominator engine (Lot 245) was designed in 1949 by Bert Hopwood as a 500cc pre-unit twin, and was later available in 600cc and 650cc forms. The beautifully compact 5T Triumph Speed Twin engine of 1938 had shown Norton the way to go, but Norton took it a whole lot further when it ultimately morphed the Dommie platform into the mighty 1962 750cc Atlas parallel twin which, with mods, later went into the Commando. Royal Enfield, meanwhile, had launched the 700cc (692cc) Interceptor parallel twin in 1960, and the 750cc (736cc) Series 1 Interceptor in 1962 (also a parallel twin). A few years later, BSA and Triumph followed with their own 750 triples.

If any (or all) of this takes your fancy, and if your pockets are deep enough, you've got a little time to make your play. Alternately, those of you guys out there who never actually ride your classics (and we've got all your names) could try sectioning whatever you've got oxidising away in the garage. But take note: it ain't as easy to do as some folk think.

Meanwhile, here are a few links on the Las Vegas Sale which is shaping up to be a record breaker, and maybe the biggest motorcycle auction frenzy of 2015.

— Big End

[Dick Mann BSA Gold Star flat tracker sale]

[Dick Mann Matchless G60]

[Mike Hailwood FB Mondial 250 Bialbero sale]

[Francis Beart Norton 350 Manx GP Racer sale]