Trease Harley 1300: Down-under, down home Special

Bike Profile

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Australia’s flourishing Historic racing movement attracts a huge variety of esoteric bikes of all ages – many wonderful, a few occasionally weird. John Trease’s Harley Special might seem to those unaware of its improbable performance and remarkable race record to be one of the latter. Trease himself describes it as “built in the Australian way of rough as guts to look at, but very clean on the inside.” 

In the hands of retired magazine bike tester Martin Hone, the Trease Harley broke the 260 kph/160 mph barrier down Phillip Island’s pit straight during the 2007 Island Classic. That was all I needed to be convinced that this rough ‘n’ ready looking device was something special. Trease Race Engineering’s small-time setup is on aptly-named Quick Street in Melbourne, and the latest manifestation, like its predecessor has been created on a shoestring. As one of its rivals puts it best – “It’s awesome when it holds together – which thankfully for the rest of us, isn’t always the case!”

John Trease, 59, has been high on the Hog ever since 1979, when he started a small Harley-Davidson shop in suburban Melbourne which grew and grew. So, already bitten by the racing bug after concocting a 1959 XLCH H-D Sportster to go Classic racing with, John downsized and in 1990 started a one-man machine shop under the Trease Race Engineering/TRE banner in Pascoe Vale. Harleys remained the main item on the menu, and to fund development of his racer, as well as put food on the table, TRE has since manufactured more than 850 H-D accessory Harley crankcases for big bore/stroker performance motors, as well as working on a flathead Indian project. John’s also carried the fight to the enemy by building replicas of the prewar Series A Vincent motor.

Early version of the Trease Harley.

The current Trease Harley Special is quite a different package from that first bike, though – one which Martin Hone enjoyed lots of success with [see below]. “It all happened because the old ’59 Sportster that we’d been racing was basically too heavy – we’d developed it as far as we could as a heavyweight hotrod with a stock frame,” explains John. “So we built a new one that was bloody fast and pretty furious, with the same engine in a much lighter chassis – but it took a good half-dozen years to get everything sorted out. Things like suspension tuning and swingarm position, sprocket height, and all those other crazy things that are part of getting a bike to handle. But we finally got it all sorted, so except for a few minor hiccups, it goes pretty well now – fast enough to keep up with the Vincents and beat them!” 

To create what’s euphemistically called TRE’s ‘New Bike’, John uses the same self-created engine replicating a 45-degree V-twin ohv Harley pushrod design that he’s been developing for the past 25 years, now measuring 95.25 x 88.90 mm for a capacity of 1298cc – just within the Unlimited class’s 1300cc ceiling. This runs on methanol and is nominally derived from a late ‘50s XLCH Harley Sportster’s Ironhead motor. The replica cylinder heads however come from the Panhead engine of the same era, for the good reason these were made in aluminium, permitting a massive 21kg saving in weight compared to the Sportster’s cast iron heads and cylinders. Trease has made his own alloy barrels with cast iron liners to “fill up the space between the heads and the crankcase, nothing more”. The crankcases are also replicated to the standard Sportster design, but with Timken taper roller bearings on both sides of the specially made flywheels retaining the original diameter roller bearing crankpin. Running a Timken bearing on the camshaft side as well stops them from “butterflying”, so that the end float under heat expansion is taken up, resulting in a smoother engine, states John. Conrods are Harley’s traditional knife-and-fork type created by Trease himself in H13 steel, carrying three-ring pistons using American-sourced blanks machined up locally in Melbourne.

Left: John Trease. Right: The 1959 XLCH H-D Sportster based 1300cc engine.

Using the Panhead top end also brings improved breathing, as well as better squish for improved combustion, says Trease, who runs a very high 16:1 compression ratio on the motor, to aid acceleration. No wonder he needs a set of rollers driven by his Holden ute to start the thing – bump starts are simply not on the agenda! “The Panhead top end closes the valve angle up about five degrees, and makes the combustion chamber around 6mm shallower, which lends itself to a better squish arrangement,” says John Trease. “Looking for power is all about the combustion chamber – that’s where it all is!” 

John has extensively ported these cylinder heads, to improve on the stock H-D Panhead design which he says is ‘really quite horrible’! The soupbowl-sized oversize valves operated by Trease’s own design of camshaft measure a huge 51mm for the titanium intakes, which John says he got from ‘some old racing car motor’, and 43mm for the stainless steel exhaust valves, each fitted with Indycar springs as used on current Ford and Holden V8 Supercar racers. They run 250 pounds seat pressure, and will allow the engine to rev safely to around 11,000 rpm in case of a missed shift, says John – although peak power of 120 bhp is delivered to the rear wheel at just 6,600 rpm on the TRE dyno. Fuel is supplied via a pair of car-type SU carbs (38 mm equivalent), converted from their usual automotive-style butterfly throttle to a cylindrical-slide CV arrangement, while a purpose-built exhaust system features twin separate 54-inch long pipes. “I’d liked to have joined them, but it was a cornering nightmare for ground clearance,” says John. The power is laid to the rear wheel via a five-speed gearbox entirely made by Trease on his own gear-cutting machine, with multiplate dry clutch and belt primary drive, using pulleys he also manufactured himself.

The ignition system has come in for the Trease treatment. This sees the H-D cylinder heads converted to dual ignition via secondary twin 10mm sparkplugs slotted down the centre of the Panhead rocker box. Providing the sparks entails a very unusual twinned magneto setup, comprising two Lucas housings welded together using Fairbanks Morse coils and rare-earth magnets, running just 23 degrees of advance. “The only people making rare-earth magnets at the time were in China, and they were 100 bucks each,” says John “I had to buy ten of them, or they wouldn’t do the job – but that spark is so fierce, it’ll almost weld metal!” The Harley-type Fairbanks Morse coil is a twin-outlet design, so with what are effectively two separate magnetos, there are two coils, each giving two separate outlets and thus two spark plug wires to each cylinder.

With its hat removed, the bike’s internal organs become obvious.

This remarkable motor is housed in a modified Featherbed frame sourced from a 500cc Norton Dominator road bike, says John. “I had to do a lot of work on it,” he admits. “Initially we put the engine in so it only just fit, like a shoehorn – we had to stretch things, bend things, shave things, squeeze things, it wasn’t very nice to begin with, and didn’t handle till we rethought the layout. Then we also had to chop out the rear of the chaincase to make room for the belt, and tilt the engine to get the sprocket height to make it handle properly.” With the current TRE swingarm that’s essentially a replica of a Manx Norton’s with twin Koni shocks, wheelbase has been shortened to 53.0 in./1346 mm, partly by steepening the rake angle for the replica Harley forks to 24.5 degrees. “I remade the forks in 80-ton steel to make sure they wouldn’t bend,” says John. Brakes are homemade, too, with a clever Trease modification to the replica eight-inch twin-leading shoe Manx Norton front drum, which usually uses 1 inch wide brake shoes. By machining out the inside of the wheel he’s now installed 2.8 in. wide shoes in what is still a 2LS layout, but with two sections to each leading shoe. “It’s because that way you can wrap the shoe almost around the inside of the brake drum,” says John. “And when you get uneven expansion between the brake drum and the shoe, the shoe doesn’t open up and jam, so it doesn’t risk locking up when it gets hot.” The rear SLS brake is a replica Norton Dominator drum.

But the most obvious change is in the whole architecture of the bike, which sees the 18-litre fuel tank removed to beneath the seat, with the filler under a flap in the tail, so that in best modern Superbike style what looks like the fuel tank, actually isn’t –  it’s the carb cover, where the airbox would normally be nowadays on any four-stroke racer. “We were getting so much wheelspin out of corners, I had to move the weight of the fuel tank to the back to get the tyre to hook up,” explains Trease. “I made it look like a seat with a normal oil tank under it, just to keep the appearance right – the real oil tank is underneath the gearbox, and it only has a single oil pump which supplies pressure fed oil to various components. It’s then scavenged via a reed valve to the top of the gearbox, then into the tank.” 

Down Under thunder. Sir Alan Cathcart gets to grips with the Trease Harley.

The chance to try it out for myself at a Ducati Owners Club of Victoria track day at Phillip Island (grazie, amici!) unlocked the secrets of what is pretty much of a mystery bike – surely the fastest pushrod Harley road racer in the Southern hemisphere.  I swear the earth moved just a little bit as the Harley motor lit up on the rollers – it’s a very long time since I’ve heard such an unbelievably angry, power-packed and just plain loud exhaust note as the Harley Special’s, although at the 2500 rpm fast idle speed John has chosen to try to counter the effects of engine braking when stopping for turns, it’s more threatening than violent. The engine is uncannily, incredibly smooth for a 45-degree pushrod V-twin with no balance shaft. You have to try to push your body weight forward by weighting up the footrests, just to stop it lifting the front wheel out of a slow turn like Honda or MG, especially with that rearward location for the fuel load. This bike accelerates better than any late-‘50s Panhead Harley has a right to – indeed better than ANY pushrod Harley of the pre-Evolution motor era. Phew! Is this an impressive motor, or what??

Yet that claimed 120-horsepower output isn’t delivered in a peaky manner with a squeezed-up powerband. In best Milwaukee V-twin tractor style, it pulls cleanly away with minimal clutch slip literally from idle – just as well, since the clutch action is quite stiff, presumably on account of having it handle all that grunt. The V-twin motor has a completely linear build of power, running strongly but so-smoothly to the nominal rev limit of 7000 rpm – though it’s safe to 11,000 revs thanks to the reworked internals and those Indycar valve springs. You can tell the internals have been comprehensively lightened by the way the motor picks up revs pretty fast, like by the way it leaps forward in second gear exiting Honda Corner for the short squirt down to Siberia. In practice, you soon learn it’s best not to run it out right to the redline, but to shift up just over 6000 rpm when you can feel the motor start to run out of breath, which lands you back in the fat part of the torque curve ready to repeat the run up the rev-scale. Trease’s choice of ratios in the homemade gearbox are spot on, with only bottom gear too low to use once on the move – no need to, though, with that great spread of power and torque.

The riding position on the Trease Special’s Featherbed frame is like no Manx Norton’s I ever rode – and I have sat on a few! It feels much more close-coupled than the usual stretched-out Manx stance, presumably because of the shortened wheelbase, even with the wide-spread, high-set clipons attached to the Trease-made forks, which are held by vestigial triple-clamps that definitely look as if they’ve seen better days. The result is a rather upright riding stance, and with that forgiving, grunty engine, the Trease Harley must be a good ride on tighter, twistier tracks than Phillip Island. But it was still quite easy to tuck down behind the broad, shallow screen down fast sections – although that was where I encountered the only real negative aspect of the handling. 

Cathcart climbs out of MG Corner at Phillip Island, ready for the straight.

This was the way that, four laps out of five, the Harley would consistently set up a straight line tankslapper past the pits, gradually twisting itself so persistently into a knot that I’d have to back off the throttle to let it recover. I tried riding through it once but the Harley started shaking from side to side in the beginnings of a determined attempt to spit me off!. After trying various changes to the setup during subsequent outings, John concluded the WP steering damper was stuffed. Pity – but the Harley handled pretty well elsewhere on the track, after the well-used Dunlop rubber cleaned up and started sticking well. 

The only other downside was the braking, which isn’t really up to the demands of such a fast bike as this one, especially one weighing in at 166 kg dry. Using the back brake hard showed it worked well, but while the front started off OK, it faded quite badly, and especially after stopping hard for Honda Corner each lap. Gradually it faded completely, accompanied by a very strong smell just to remind me what was happening! To be fair, John had been trying to get a new brake he’s working on for the bike finished in time for me to use, but ran out of time. 

But this bike is mostly about the impressive performance of that wonderfully potent, smooth-running engine which it’s a delight to use – it’s so sweet and torquey. The Trease Harley is a glorious example of the fine art of special building, a motorcycle painstakingly created and patiently developed by a single man and his brigade of helpers. As such, it’s a great example of Aussie ingenuity which, while possibly flirting with the letter of the Classic racing rulebook, is certainly entirely in keeping with the spirit of the category. Anyway, its creator has a different view on what this is all about. “This kind of racing is an engineering exercise”, says John “and when somebody goes on the track and does better than they did last time, then they’ve succeeded in achieving their objective. Robbie Hermans actually set the Classic Unlimited lap record here at Phillip Island on my old Harley back in ’97/’98, and it took me seven years to beat him with this new bike. It’s a very hard thing to do, building on the past with your eye on the future, and that’s why I plan to keep on developing this bike, and running it whenever I can. It’s a continuous process that started back in 1959 when Harley built that old Sportster we used to race, that’s in the back of the ute. We just keep trying to make it better, and faster.”

That says it all about Classic racing – doesn’t it?

Matin Hone on the Trease Harley: Lead-tipped arrow

Former Aussie Thunderbike champion Martin Hone was John Trease’s third rider during his 25 years of race tuning. “By 1988 I was doing the high-performance bike and racer testing for Australian Motorcycle News,” recalls Martin, “and one of the jobs was to ride a Classic racer for an article about Historic racing. This turned out to be my first introduction to John Trease and it all started off very casually – but as I was getting my leathers on to ride it for the magazine test, John fired up the ‘steam hammer’, which is what he called the modified Harley Sportster, and life was never going to be the same for me again! I was surprised at how well the thing performed, and mentioned that if he ever needed another rider, to let me know. A couple of months later I got a call to see if I was interested in riding it at the South Australian Titles, and so began a 20-year partnership. Winning the prestigious Southern Classic for the first time is still my most treasured win, as JT had been trying for many years to win this event to silence the many Harley sceptics.”

Martin Hone admires his ride in the pits at Winton.

“This ‘old’ bike weighed over 500 lbs, and was top heavy with slow steering characteristics making for hard work on the tighter tracks, and it was quite scary on the fast tracks like Phillip Island. We massaged the rake and trail dimensions to a nice, workable relationship, and the front end became very planted, but eventually the Sportster became less and less competitive due mainly to its weight. He figured he could make a better mousetrap by starting with a clean sheet of paper, so we came up with the ‘new’ bike, using what we had learned since I started riding for him. I was able to contact Pete Zylstra, father of the legendary XR-750 and he provided a set of blueprint drawings for a tube frame that the Harley factory was going to use to replace the one based on the road bike. It certainly helped us achieve our design goal of around 320 lbs, but was way too flimsy – the extra torque of our short-stroke 1200 motor just tied it up in knots, which would suddenly release half way round a bend! Even so, I set my fastest time at Phillip Island on that bike!”

“A succession of mods and extra bracing did little to curb its errant ways, and the extra weight was beginning to tell. JT then bit the bullet and built a replica Norton Featherbed chassis. We only ever suffered one engine failure, which was when we took the bike to the National Titles over in WA.” 

“The bike had enormous potential, but continually got let down with minor electrical and carburation problems. The consequence of all this is that we don’t have as much to show for our efforts as we could otherwise. I won the Australian Historic Title on the ‘old’ bike, but failed at three attempts to repeat that on the ‘new’ one. Of the four Southern Classic titles on the tight and winding Winton circuit that a Trease Harley has won, the ‘new’ bike was responsible for two, plus numerous Unlimited Classic race wins at Phillip Island, and the fastest bike title at the Geelong Speed Trials, a mile sprint along a curved, cobblestone-based public road next to the beach. The late Robbie Hermans won an Australian Title on it, and it still holds the Unlimited lap record at the Island, which I think was a 1:48.96 that Cal Karrick Jnr. set winning the Island Classic on it in 2006.”

“It’s been fun racing with John. He’s amazing at coming up with a succession of designs and then executing them – attention to detail and pre-race testing may not be his strong points, but the engine, structurally, is magnificent.” And all achieved against the odds.”

Story and test: Alan Cathcart • Photos: Stephen Piper and Martin Hone

OBA Issue 12
This article first appeared in Old Bike Australasia Issue 12.