Real Classic



The original Square Four engine was designed by Edward Turner in 1928.

He was trying to get work as an engine designer with a number of motorcycle manufactur­ers, using his unique engine design asa calling card to demonstrat­e his skills. The engine was considered by BSA but rejected. Ariel, however, liked the idea and decided to make it.

The early engine with two transverse crankshaft­s was essentiall­y a pair of across the frame ohc parallel twins joined by their geared central flywheels, with a square, four cylinder block and a single head. With a chain driven overhead camshaft, the early Square Four 500 used a hand change, four speed Burman gearbox. The first Ariel Square Four 4F was shown at the Olympia Motorcycle Show in 1930.

In 1932,the cylinder bores were enlarged by 5mm to give a capacity of 601cc, specifical­ly to accommodat­e owners who wanted to attach a sidecar.this model was used for the Maudes Trophy endurance attempt, covering 700 miles in 700 minutes, followed by a timed lap of 87.4mph.

The cammy engine gained a reputation for overheatin­g the rear cylinder heads, so in 1936 the engine was completely redesigned, emerging as the 1937 ohv 995cc 4G.the crankshaft­s of the new engine were connected together by coupling gears on the drive side of the engine. In 1939 Ariel's patented Anstey link plunger rear suspension was offered as an option. In 1946, the plunger rear suspension was available again, with oil damped telescopic front forks replacing the previous girder forks.

In 1949, the Ariel Square Four Mkl saw the cast iron cylinder head and barrel replaced by an alloy head and barrel. Even with this 301bweight reduction, the 1949 machine was still no lightweigh­t at around 4351bdry. The rather constricte­d and tortuous inlet tract, small valves, conservati­ve valve timing, low compressio­n ratio and car like combustion chambers all constraine­d power to 35bhp at 5500rpm. The Mkl, by contrast, was capable of 90mph plus.

In 1953,the four pipe 997ccmk2 was released with a re designed cylinder head to improve cooling and breathing, with four separate exhaust pipes from two cast aluminium manifolds and a rocker box combined with the inlet manifold. The frame was redesigned to accommodat­e the tall, car type Sucarburet­tor and the oiling systemwas updated with a gear pump which replaced the antiquated plunger pump. The Mk2's better breathing arrangemen­ts delivered 40bhp, and this Ariel was capable of 100mph (just). It weighed 4251band cost £336.16.6.

In 1954, Ariel built a Mk3 prototype with Earlesfork­s and swinging arm, but the model was never put into production. Over the years, various other swinging arm Square specials have been made.

The Square Four found a new lease of life in the

1970s when the Healey brothers produced the Healey 1000/4. The brothers tuned and upgraded Ariel engines for racing throughout the 1960s, and when

Ariel ended Square Four production they obtained a large assortment of spare parts. The Healeys updated the engine with a special camshaft, increased the compressio­n ratio to 7.5:1 and improved the lubricatio­n system. Power increased to 52bhp and the motor was installed in an Egli style frame, incorporat­ing the oil tank, with Metal Profile forks.

The Healey 1000/4 was well received when launched at the 1971 Earls Court Motorcycle Show. It weighed lessthan the contempora­ry Honda 250, it handled well, and achieved a top speed of 126mph when tested. But it couldn't compete with the cheaper and faster Japanese superbikes of the 70s, like the Honda CB750. Production ceased in 1977 after 12 bikes were built, which means that the few surviving Healeys are highly sought after.


Eightweeks­after my Ariel left the Uk,it cleared custom sand abio hazard inspection. the stripped framewasso­onon my benchand I wastest fitting the enginebott­om end didn't look right. the engine was can ted up by about 10degreesa­nd,with the bend in the top tube kickingthe front forksout, it would have looked like it had saggedin the middle.perhaps the original builderwas­going to fit longerfork­s or turn it into a chopper?on a positiveno­te the engine and gear box plates were OK.

After a lot of measuringa­nd dithering,i finally got the angle grinder out. the first job was to cut the lower frame tubes just before they started curving up to get the engine and gearboxto sit level.thenextjob wascutting out the curved sectionof the top tube and installing­a temporary sleeve.after a few tries I got the enginesitt­ing leveland the restlookin­g OK.

I made some lower frame tube extensions that lined up with the lower mounting points on the frame plates, and tack weldedthem in place. Clampingth­e front down tubes on the front engine plates,i measuredth­e length of the slug for the top tube.theendsof the slugwerema­de

a tight fit in the frametube. Hourswere spent with a tape measurea, long steelrule and an inclinomet­er getting the top tube lined up before tack welding the slug in place.

With everything lined up, my attention turned to the engineand gearboxpla­tes... knowing someof the frame holeswere now in the wrong place.drilling new holeswasea­sy,but moving holes side ways involved a lot of filing and then filling the redundantp­art of the holeswith weld. After severaltri­al fits and double checks,the frame was profession­ally welded before blasting and powdercoat­ing.

Next:the enginebott­om end.

Takingit apart wasn'tthat difficult exceptthe two drive gears were a really tight fit, requiring a lot of heatand pulling beforethey cameoff.the only significan­t issue was the front timing side main bearing that had obviously spun. with new big end bearingsan­d bolts it all went together quite cleanly.the cylindersa­nd pistonswer­en't too bad and,after a light hone,somenew rings and improvised­ring clamps,it all slipped into place.

Whileworki­ng on the bottom end I could see glimpses of turner' s other famous design, the

Triumphtwi­n: the camfollowe­rslook identical.

The cylinder head was altogether another matter.all the studs had been repaired,one of the spark plugs came out with part of aH eli coil attached, and two of the valves were stuck open! Someof the stud repairswer­e badlydone,with He li coil inserts standing slightly proud and burrs around someother holes.the only sensible thing to do wasto removeall of the studs,fix the problemsan­d checkthe headwasn't warped (a common problem ). one of the studs came out with all the headthread still attachedto it. Hoursof work, dressingth­e areasand Helicoils that were proud and makinga double diameter replacemen­t stud, finally produced a flat cylinder head face. the valve guides were checked with a reamer(two weretight), all of the valveseats were recut and valvesgrou­nd in.

Fitting the cylinder head correctlyi­s a long tediousjob, with 20 nutsto fit andtighten in a fixed order.the nuts hidden in the cylinderfi­ns can be a bit fiddly, as is getting an eventorque setting on them all. Blowncylin­der headgasket­s havebeena problemwit­h Square4s, but the mo de rnotiosu per gaskets( available from Draganfly)and following the tightening down

instructio­ns religiousl­y can produce a good seal. The gaskets continued to settle so they were re torqued afterthe initial ridesdurin­g running in.

The next challengew­asthe Burmangear­box. None of the chain lines seemed to quite line up. Further checking revealed that it was the wrong gearbox,from a twin, with the input shaft modifiedwi­th a crudeadapt­erto replicatet­he longer main shaft needed for a Square 4. I was not best pleasedw, ith a mutilated mainshaft

I am unlikely to recover anywhere near what

I paid for it. Thecorrect Square4 Gbburman gearboxesa­relike hen'steeth. After months of fruit less s ear chingt, he correct box popped upon Drag an fly' second hand list. I have never been on the phonesoqui­ckly.

The box slotted in perfectly and the chain lineswere much improved.a smallamoun­t of shimminggo­t them dead on.i shouldhave stripped the gear box and perhaps questioned why it was a second hand box, but enthusiasm got in the wayandfitt­ing the boxallowed­a whole hostof otherjobs to be completed.

The primary chain ca seisin three parts. the front half of the inner cover is part of the drive gear cover;the rearinner chaincaseb­olts onto the front inner coverand a full length outer cover completest­he chaincaset. heouter coversare proneto damageandt­he only one I could get had a broken engine shock absorb er dome. after cleaningup the damagedare­a,a dome wasmade andwasglue­d in placewith epoxymetal.i did consider welding the geriatric die cast aluminium but it is extremely difficult to achieve a clean join. Thefinishe­djob lookssligh­tly different to standardbu­t doesnot lookout of place.

The cylinder head exhaust stubs were badly worn. weighing up different repair methods, shrinking on thin steel sleeves seemed the bestapproa­chand seemsto haveworked. Exhaust pipes were stainless steel square 4 pipesfrom Armours. Liningup the pipeswith the Hunt master frame and silencers took a few squigglybe­ndsand a sleeveat the silenceren­ds due to different pipe diameterst. he cut, shut and bent pipesare far from perfect and another set will probably be madewhen time permits.

The carburetto­r should be a Solex,but it came with theSu from a Mk2,soa conversion plate was madeto accommodat­ethe different mounting bolt positionsa­nd borediamet­ers.i have extensive knowledge of Amalcarbsb­ut knew nothing about thesesmall­susa. rebuild kit and a new dam per spring from Draganflyw­erea good start and it seemedto go together fairly easily.

The clutch cover was a looked like somebody had playedfoot­ball with it. An hour's worth of panelbeati­ng got it backroughl­y in the right shapeso it would fit (moreof this later).i hope to find a better one on my next trip to the UK.

Thelengthe­nedtop tube presenteda problem with the petrol tank; a standardta­nk was now too short. Fortunatel­yi had a rather battered BSAA10 plunger tank that seemed to fit after cutting off the front mounting ears (easily replaced ). after blasting the tank to bare metal, substantia­ldents were pulled out and cracksweld­ed up.the protracted processof priming, filling, rubbing down, priming, filling, rubbing down,etc,took a numberof cycles beforethe tank was readyfor a top coat.

At this point I should haveusedth­e tank sealantbut applied it after the top coat, definitely a mistake! despite extensive precaution­s there was a small spill on the paint work. worse, the cling film usedto protect the paint finish caused fine markson the new paintwork.after another rub down andre paint, a local car painter applied a coat of two pack clear spray, the only finish that seemsto copewith modern petrol.

Thechanget­o the tank alsomeantt­hat the seat had to be altered. rather than modify an existingse­at,i madea new seatbase

out of 20mmply.a relatively simple bit of woodworkin­g, with a fibre glass cover over the rear mud guard cut out. A local vehicle upholsters madean excellentj­ob of coveringth­e seat,but I specifieda steppedsea­twhich wasa mistake. It was too cramped for me. I subsequent­ly had the seat recovered with a thicker flat top.

The bulk of the cycle parts are standard ariel items and didn't presentmuc­hof a challenge, particular­ly with the excellent parts avail abiil ty from Draganflyi. re spokedand trued the wheels, fitting Hi eden au tyres, with these mi rib bed K 44 3.25x 19onthe front andthe blockpatte­rn K344.00x19ont he back. the classic hi eden au tyres, as supplied by Wheel house tyres, look the part and aremadeof modern rubbercomp­ounds that grip well.

My first attemptsat startingth­e machinewer­e not promising. the engine was rather stiff to kick over,with intermitte­nt backfiresi­n the exhaust and theSu carburetto­r occasional­ly flooding. a quick checkwith the sparkplugs­out revealed weakand intermitte­nt sparks. Suspicionf­ell on the distributo­r cap: a good cleanhelpe­dbut it wasstill not right. Fortunatel­ya friend had a brand new austin 7 distributo­r cap, the same item as the Ariel. combined with a Magneticpo­wernz electronic trigger system produced excellent sparksat all the plugs.

After resettingt­he carburetto­rfloat level,the secondatte­mptsat starting the machinewer­e an improvemen­t but not by much!assoonasit fired there was sound like a fire bell going off in the primary transmissi­on a. ft era quick shut down anda bit of headscratc­hing, removingth­e clutch cover revealed witness marks, confirming my suspiciont­hat the clutchwash­itting the cover. Attacking the clutch cover again with panel beating hammer sand some washers under the mounting screws solved the problem.

Thingswere­going better,but a quick ride up the lanereveal­edthat it seemeda bit constipate­d.

It didn't sound right and neededquit­e a bit of throttle to tick over.i decidedto go backto basicsand check valveand ignition timing. Removingth­e front crankshaft­end coverto turn overthe crankshaft revealedwh­y the engine had beenstiff to kick over.thecranken­d nut wasrubbing on the end cover.somedeft work on the lathe soon fixed that. Turningthe engine over revealedth­e ignition timings were spot on, but the plug leads to #2 and #3 cylindersh­ad somehowbec­ome crossedove­r.with the leadson the right spark plugs she purred into life first kick,idled nicely and shot up the lanelike a scaldedcat.

To protect the freshly painted and vulnerable petrol tank, all the early tests were undertaken with a smalltest tank strapped to the top tube. After sorting the problems of fitting the tank and plumbing it in, the rest should have been a doddle ...

With four litresof fuel, however,there waslittle or no fuel flow. Initial suspicionf­ell on the fuel taps. Had I bought reservetap­s with extended fuel pick ups? the taps checked out as normal, so I poked a drill up into the tank... to find a blockage. i suddenly remembered that these Bsatanks had separatefi­lters that screwedup into the tank these must now be coveredin tank sealant doh!

Initial test rideswere very promising. loads of smooth torque, comfortabl­e sitting position and beautiful sound. Howeverthe­re were someteethi­ng problems.oil leaked profusely from the gearbox. rene wing the outer case gasket significan­tly reduced the flow, but it lookslike I should havereplac­edthe inner cover gasket at the same time. the gear box is notably noisier in third, not an uncommon will be addressedw­hen the box is takenapart to fix the oil leak.theclutch was dragging a bit but improvedwi­th adjustment, although it's still not right. Anotherjob to address when the gearbox is taken apart.the cylinder headstill seemsto be settling down, requiring the head nuts to be regularly re tightened.

Twiceunder braking,while turning right, the steeringse­emedto lockand the front wheelfelt likeit wasabout to slideaway. Releasingt­he front brakefreed up the steering.i spotted a witness markon the mudguardan­d the penny dropped. With the front forks compressed­under braking, the mud guard touched the left hand exhaust pipe,but this didn't happenwhen turning left. Another light bulb moment:the main part of the engine and cylinder block sits about two inches right of the frame centreline becauseof the crank shaft coupling gears. Slightly shortening the left hand pipe and bending it out to the left createdthe neededclea­rance.

The most painful part of getting the Ariel on the roadwasthe legalproce­ssof registerin­git, involving government department­s extracting large sums of money from my wallet. the first part of the process was al locating a 17 digit Vinand attachinga plateto the machine. The secondpart wasa'low Volumevehi­cle Certificat­ion' because of the frame modificati­ons and engine change. The nearest motorcycle certifier is almost 150 miles away! the absence of a registrati­on document meant applying for alternate document approval. the final part was a compliance check for an imported vehicle which duplicated most of the earlier tests, then registrati­onand a number plate.

Thefinal insult wasthat the registrati­on authority insistedit be called an Ariel Huntmaster asthis iswhat it originally was!thetotal bureaucrat­iccost was £650,not including transporta­tion and expenses...


Sowhat'sit liketo ride?turnon the petrol and pull up the enrichment lever on theSu ca rb, then a couple of healthy swings normally bring it rustling into life. It can be a bit cold blooded, so the enrichment lever is slowly lowered as it warms up. Oncefully warm after a short distance, the enginewill settle down to an eventickov­er.

Unlessthe clutch hasbeenfre­edoff before starting, first goesin with a very definite clunk. Pulling away is extremely smooth, thanks to a progressiv­e clutch and load so flow speed torque.

Accelerati­onis brisk,with none of the harshness usuallyfou­nd with singlesand twins.gear changes are deliberate and best not hurried but, given the acres of smooth torque, this is not an impediment­to swift progresst. hefour certainly buzz es along and feels under geared. I have a sneaking suspicion that it is running on side car gearing and will change the gearing when I takethe gearboxapa­rt.

The handlingis slightly on the slowside, just right for touring. the weight distributi­on, slightly longerfram­eand riding positionma­ke for a comfortabl­e ride. the machine holds a line nicelyand is not easilymove­doff its line by bump sand pot holes. the exhaust pipes are slightlyfu­rther out than the Huntmaster'sand will touch down if pushed,but this is not the machinefor getting your kneedown on!

The only disappoint­ing itemsareth­e brakes. On paper,and lookingat the qualityof the shoesand mechanismt,hey shouldbe good, but they lackinitia­l bite. Don't get me wrong, they aremoretha­n adequatebu­t they promised more.i hada Bsaa10with the samebrakes back in the 1970 sand they were disappoint­ing too. The Bsasingle sided8" brakefelt much better.i hope the brakes will improve after fully bedding down and further adjustment.

Most swingingar­m Square4s usethe Mk2 enginewith the four exhaustpip­es,so visually different to Mkl based machine st. hemkl with two exhaustpip­esand its moreconser­vative looks can initially be confused with at win. I tried to emphasiset­his conservati­velook with the classicmau­veand blackpaint scheme.

Wasit worth the all effort and did it meet my original goals?my answeris a resounding yes.thereareaf­ew machinesth­at you immediatel­yfeel comfortabl­e on and which give you confidence. despite a few niggles, this is one of those machines.if only the brakes were better, and maybe the engine could be a bit more powerful... Re

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 ??  ?? Two views of Stuart's modified frame, as it was when he collected it, prior to steam cleaning, and as it finally arrived in New Zealand
Two views of Stuart's modified frame, as it was when he collected it, prior to steam cleaning, and as it finally arrived in New Zealand
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 ??  ?? Ariel's square top end, hopefully showing how it fits together
Ariel's square top end, hopefully showing how it fits together
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 ??  ?? Thecylinde­r head, before and after repairs
Thecylinde­r head, before and after repairs
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 ??  ?? Well on the way
Well on the way
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