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We want it: History in the metal

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Spark plugs: What you need to know

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The moment of truth

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January 2025

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Batteries: What you need to know

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Chains: What you need to know

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Classic TT returns

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Enfield Classic 650

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December 2024

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November 2024

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Egli-Vincent

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Snake Pass threat

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October 2024

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Tonkin’s TT tales

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Become a Classic Bike subscriber

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A match for a Manx

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SKY HIGH HILLCLIMBING

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Stately pile-on

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Get up for the Kop

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Time for a T140?

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Rick’s Fixes: cold comfort in the shed

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hole sideways

Did this Curtiss really do over 136.36mph at Ormond Beach, Florida in 1907? Nicksy thinks not...

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A RECORD OF EXAGGERATION

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HOW TO: MAKE A JET BLOCK EXTRACTOR

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BARON’S STROKE OF BAD LUCK

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How To: Make vintage bike grips

HOW TO: RECYCLE OLD CAR PARTS

THE ISLAND’S BIGGEST DRAW

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KEEPING THE FAITH

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HOW TO: FIT AN AMAL CARB TICKLER EXTENSION

HOW TO: REPLACE BSA BEARINGS

Offers and Competitions

Latest Competitions

Latest Offers

Features

Rick's Fixes

Mike Nicks

Magazine

Magazine Issues

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Subscribe to Classic Bike Magazine in our January Sale

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Get set for showtime!

**Save up to 82%** on a Classic Bike Subscription in our January Sale with **3 issues for £3**

_Classic Bike_ magazine helps inspire you to get more from your passion for classic motorcycles. It's not surprising it's the UK's best-selling classic motorcycling magazine when we share your fascination with motorcycling's heroic past.

Every month it's packed full of real motorbikes you love to own and ride from the 1960's onwards. Every issue is packed full of great bikes, rebuild projects, practical workshop tips, buying advice and fantastic tales of full-noise, high-octane, unfiltered motorcycling.

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Grab your tickets now, as the Devitt Insurance MCN London Motorcycle Show roars into town February 14-16, 2025. Celebrating the best of all things two wheeled, the show promises displays of the very latest models from the world’s leading manufacturers, a live action extravaganza which will see racing heroes go head-to-head, three fantastic stages hosted by your favourite motorcycling celebrities, the latest premium kit and accessories at bargain prices, with much more still to be announced.

Come and see the latest 2025 models on display from the world’s biggest manufacturers, featuring Honda, Ducati, Harley Davidson, Kawasaki, KTM, Triumph, BSA, CF Moto, Agusta MV, Artisan Electric and Royal Alloy. More coming soon!

**Live flat-track fun**  
Prepare for hair-raising live flat track racing action as the biggest names in British biking battle it out on a thrilling indoor circuit. A purpose-built indoor flat track circuit, a squadron of Britain’s best biking talent past and present, and three days of adrenaline-pumping action. How does that sound?

Taking place inside London’s ExCel, riders include 23-time Isle of Man TT winner John McGuinness, and current TT lap record holder and Bennetts British Superbike star Peter Hickman. The pair will be in the mix among more of Britain’s top racers competing on a tailor-made flat track circuit in an effort to become the 2025 Devitt Insurance MCN London Motorcycle Show mini indoor flat track champion.

**Henry Cole Live Stage**  
The new-for-2025 Machine Mart stage sees TV’s Henry Cole, Allen Millyard, and Guy ‘Skid’ Willison, come together to tell unheard stories, provide plenty of laughs, as well as astounding you with their legendary motorcycles and engineering expertise. Fans will also get the opportunity to meet Henry and his guests for a chat and even a quick selfie!

**Boorman’s back**  
The king of motorcycle adventures returns to host the popular Charley Boorman Adventure Base Camp stage, supported by Oxford Products. Expect new tales from his latest TV trip, the

Long Way Home, a pannier load of useful tips and tricks to use while planning your next adventure, and how to overcome challenges on the road and plenty more insights from the Long Way series star.

## Save cash by booking advance tickets now

#### This is incredibly original **1930 Scott Sprint Special** was ridden by Roland Stobart in the Manx Grand Prix of that year. We love the way it looks and the fascinating story behind it

WORDS: **MARK GRAHAM** PHOTOS: **VERRALLS**

Talk about provenance. This motorcycle is surely one of the best vintage two-strokes with the most storied background you can buy. A factory machine with unimpeachable history – that also happens to be a scream to ride – does not come better than this.

Scott’s entrants for the 1930 Manx Grand Prix were Noël Mavrogordato (better known as ‘Mavro’) and Roland Stobart, who also rode a bit of speedway. Both had been ‘up’ at Cambridge University together before they visited the Scott Competition Department at the Shipley, Yorkshire factory to spec-up their ‘mounts’ for the Manx.

Mavro favoured the early singledowntube frame, despite a duplex version being available, and Stobart opted for the same. The Auto Cycle Union was heavily against thinly-disguised factory bikes entered in amateur events and the term ‘shamateur’ was coined to heap scorn on these entrants. But as with almost any form of competition, anyone serious about winning regards the rule book as merely advisory.

Both machines were converted to foot-change gearshift, while frame lugs for sidecar use remained in place to lend a hint of ‘hardly deviating from standard’ to the bikes. The huge, flared fuel and oil tanks (oil filler on the left for IoM pitlane practice of the time) must have been a slight giveaway, and the presence of well-known Scott race mechanics in the pits on Glencrutchery Road must have further incensed the ACU.

Stobart finished 15th in the Manx Senior with a race time of 3h 29m 57s at an average of 64.71mph. Mavro scored a DNF. The Stobart machine began with a 596cc engine, changed by the factory to a 498cc unit (stamped ‘SP’ for spare) All the numbers stack up and it comes with its original reg number on a V5.

Few vintage machines look better than a Scott stripped to the bone for competition use, and this is one of the most handsome you’ll see; blindingly original too. Scotts have always been undervalued, and the £27,500 Verralls are asking for this ex-Stobart gem is more than reasonable.

More interesting than any early Norton Manx, it’s still a 90mph machine. As Mavro replied when told he could no doubt win a Manx GP on a Norton: “I daresay, but I’d rather lose on a Scott”. **:a[verralls.com]{href='https://verralls.com' }**

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#### We barely give them a second thought except when they break down, but these mini marvels of steel and ceramic have some clever secrets

‘I try to replace spark plugs before they fail, but only use the fancy ones when they were an OE fit. So my 2005 Fireblade gets expensive iridium, but my 1972 Commando gets old-style copper.’

A spark plug conducts a high-voltage (up to 45,000 volts or more) low-current pulse sent to the plug cap from an ignition coil. This then jumps the air gap from the centre electrode to a side electrode and ground (earth). A conventional side electrode covers the tip of the plug, though some leave the centre electrode more exposed to the fuel/air mixture.

The plug must work within the correct heat range for the engine it is specified for, usually between 400 to 800°C. Plug manufacturers cater for different engine types with a range of spark plugs featuring differing lengths of insulator nose. A long insulator maintains the temperature in the plug – these are called ‘hot’ or ‘soft’ plugs and are usually fitted in low-revving, low-performance engines.

A short insulator nose absorbs less heat and with more of the insulator in contact with the shell, heat is rapidly dissipated from the plug. These are termed ‘cold’ or ‘hard’ plugs and are usually found in high-revving, high-performance engines.

Modern plugs have a wide heat range, so you need good reason to deviate from the recommended fitment, but a slightly hotter plug may reduce fouling if most of your riding is bimbling in town, while a tuned engine may run better with a slightly colder plug.

Modern engines often use projected nose-style plugs in which the electrode and the end of the insulator extend a little further out of the plug. This allows quicker plug heating to reduce fouling, and also takes advantage of the cooling effect of incoming fresh fuel/air at higher revs. Plug manufacturers design their spark plugs for the type of engine your bike has, so this isn’t a variable you need be concerned with in plug selection.

In a copper spark plug, the central electrode is usually made from a heat and fuel-resistant nickel alloy with a copper core. Copper is a popular choice for plug construction, because it offers good conductivity of electricity plus the ability to dissipate heat. Copper also has the advantage of being cheap, making this type of plug an economical choice.

The more basic the engine, the more basic the plug required. A magneto engine will be happiest with a copper plug without a resistor to match the lower energy of the system.

**\- Cons** Less resistant to erosion and not as forgiving of high temperatures

Higher-end metals such as silver, platinum, palladium and gold are sometimes used in the electrode alloy for their anti-erosion characteristics, or improved conductive properties. For example, gold is more resistant to corrosion and silver conducts better than copper. The iridium you often hear talked of in the context of spark plugs is a member of the platinum group of elements. They promise easier starting, greater efficiency and longer life. However, these benefits are really most tangible when they are used in high-revving, high-compression modern engines.

**\+ Pros** Longer service life, better guarantee of spark efficiency

The spark of a surface discharge plug goes sideways from the centre electrode to the side electrode, which can be the metal shell itself. This gives the centre electrode unhindered exposure to the fuel/air mixture and theoretically keeps the electrode cleaner because the spark stops deposits forming on it. It is also intended to slow erosion by giving the spark several paths to earth, therefore keeping the side electrodes cleaner for longer.

These plugs are something of a niche and really only benefit hard-worked modern race engines. Probably not worth the expense for most of us.

**\- Cons** Expense, limited range of fitments

The specification of a plug is indicated by the code on the insulator. The really important bits are heat range, thread size, reach and the material used in the plug’s core.

Typically, an NGK CR9E has a 10mm thread with a 16mm hex (C), a suppressor resistor (R), is 9 on the heat range (from 2 hot to 12 cold) and a reach of 19mm (E), which is the length of the thread. There may also be a letter denoting the firing end construction – for example a BR8ES has a standard copper core (S). This might be also be followed by a number which denotes the required gap in tenths of a millimetre (where there is no number, the gap is 0.7-0.8mm).

Different manufacturers use different codes and Champion’s heat range numbers work in the opposite way to NGK; high numbers are hot, low numbers are cool. Your bike shop and the internet have cross-reference charts if you want or need to deviate from the manufacturers OE fitting.

#### **What are typical failures and when should plugs be replaced?**

Given that a plug sparks thousands of times every minute, it’s not surprising that side and centre electrodes are prone to wear. The combination of extreme heat and vibration can damage insulators – and then there’s the constant attack from oil, carbon and combustion byproducts.

Older four-strokes that burn a bit of oil will foul plugs and, while they can be cleaned with a copper brush and brake cleaner, they will need more frequent replacement. Modern oil improves plug life on two-strokes, but they still need replacement more often than four-stroke plugs.

Check conventional copper plugs for gap and condition every 4000-5000 miles and replace at 8000-10,000 miles. Iridium plugs have longer inspection and replacement intervals of 15,000 and 30,000 miles or so. And only buy plugs from a reputable source; there are lots of low-quality fakes around.

**Photography** NGK, SIMON BELCHER/ALAMY & SHUTTERSTOCK/DEZAY

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#### At the British Speedway Final on July 30, the new **Weslake** speedway engine swept its riders to first, second, fourth and fifth places. Peter Collins was second on the night, but went on to win Weslake’s first Speedway World Championship the following year

**I**n the mid-1970s, as the established British motorcycle industry lurched from one crisis to the next, there were still flickers of hope in UK based manufacturing and development. The Weslake speedway engine was one of them.

Weslake were a well established research and development engineers with a particular specialism in gas flow and four-valve cylinder heads. Company founder Harry Weslake had biking history going back years. During World War I, while still in his teens, he’d taken out carburettor patents. In the 1920s he prepared Sunbeam motorcycles for racing at Brooklands and developed a gas flow meter to test cylinder head efficiency. He went on to work with Bentley, Jaguar, Vanwall and other British motor industry giants. In the 1960s, among other projects, he developed the V12 engine for Dan Gurney’s Eagle Formula One car and made four-valve conversions for Triumph parallel twins.

The speedway engine wasn’t a commission. It was a response to the idea that the firm could build a four-valve engine that’d outperform the dominant two-valve Jawa, and which might be a commercial success.

Work had begun in 1974 and the prototype engine first ran at that October’s International Grass Track meeting at Lydden Hill in Kent, having been hastily assembled the day before. Ridden by Don Godden, who was involved in the bike’s development, the bike performed well in the final, but was thwarted by a lack of sparks. Peter Collins won on a Jawa, but he’d definitely noted the Weslake’s performance.

In December, with the engine now in a speedway frame, it was tested at Hackney Speedway track by Ipswich captain John Louis. He was impressed enough to order two units for the start of the speedway season in the following March.

The new engine used a flat-top piston and a narrow valve angle, with a pent-roof cylinder head. The four valves were opened by pushrods and the rocker layout was apparently informed by the work that had been done on Weslake’s four-valve conversion for the Triumph twin. It would safely rev to 8500rpm, with peak power (of around 45bhp) at 6500rpm. The new engine was designed with the same engine mounting positions as a Jawa unit, so it could be fitted straight into an existing frame.

Despite having seen the prototype engine in action at Lydden Hill the previous year, Peter Collins – then one of the world’s top riders – wasn’t among the very early adopters.

“Dave Nourish was the northern distributor for Weslake. He took me down to the factory in spring 1975 and showed me what they were doing,” says Peter. “I hadn’t ridden one at that time. Then Dave brought an engine up for me to test at Belle Vue. I was impressed, but at the time I had the best two-valve Jawas prepared by Guy Hallet, so I wasn’t in a great rush to change. In truth, I was a bit slow.

“John Louis, Ray Wilson at Leicester and Martin Ashby at Swindon had been riding with them all season. And Phil Crump was riding a Jawa with a four-valve conversion. It was three months into the season before I raced the Weslake at the Golden Helmet competition. Phil Crump beat me, but I realised its potential as soon as I started using it. I knew that four valves were definitely the future. It was a big leap forward in terms of speed at the end of the straight and the pulling power out of corners was far superior.’

By the time of the British Final at Coventry in July, the Weslake was gaining real popularity among top riders. John Louis won on the night, ahead of Peter Collins, Malcolm Simmonds and Ray Wilson. Only Simmonds was riding a Jawa. By the end of the season, the majority of Britain’s top league riders were Weslake powered – and the success continued through the rest of the decade.

“I won the world championship in ’76 in Poland on a Weslake,” says Peter. “So I was the first world champion using a Weslake – and I stuck with them till nearly the end of my career. I was doing long-track and speedway, and the factory supplied me with about six or eight engines every year. The Weslake accelerated my career and helped me onto the very top rung of the ladder.’

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The January issue of Classic Bike takes you for a ride in a time machine, 50 years back to 1975 – join the celebration of standout events like the launch of Honda’s 400 Four, Johnny Cecotto’s mindblowing arrival on the GP scene, electric-start Brit bikes being tested, Ron Haslam beating the world’s best at Cadwell Park and Martin Lampkin winning the World Trials Championship.

Stepping further back in time, there’s a test of Norton’s first overhead cam road bike, the CS1, before hurtling back towards the present with the story of a Honda NS400R race rep restored by a perfectionist. All this plus the usual round-up of events and news from the classic world, as well as tips, techniques and project bike updates in CB’s revamped Tardis-like workshop section.

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#### Buying batteries used to be simple, even if maintenance wasn’t. But now, with multiple options available, things have got complicated. This is what you need to know

‘I’ve used lithium batteries in race bikes, but to be honest I wouldn't bother for the road. Although I do much prefer AGM to old-style high-maintenance lead acid.’

Also known as a flooded or wet cell battery. This is the conventional old-style battery in which lead plates (positive and negative) are built into a case, each separated by a rubber barrier and the plates submerged in electrolyte. The sale of the acid packs which used to be supplied with these types of batteries is now banned. If you want a lead/acid battery, you should be collecting it filled and charged, from the shop.

**Pros** Cheap. Wide operating temperature range from below freezing to 100°F-plus. Relatively low self discharge rate.

**Cons** Needs regular topping up, risk of spills means they must be mounted vertically. Discharging by over 50% can damage the battery.

Sometimes referred to as VRLA (Valve Regulated Lead Acid). Similar construction to old-style LA battery, but electrolyte is sealed into the battery and the gases created during the charging process are controlled by the valve system. Increasingly superseded by AGM batteries.

**Pros** Same as for the LA above, plus maintenance-free. Can be mounted in any orientation (except upside-down).

**Cons** Discharging by over 50% can damage the battery.

A lead-based battery with acid in gel form instead of a liquid. Specified as OE on some bikes, but have now been more or less superseded by the AGM type.

**Pros** More tolerant to deeper discharge rates than a standard LA or SLA.

**Cons** Sensitive to excessive charging voltages (over 14.4v). Size for size, will store less power than an AGM and cold weather performance not as effective.

**ABSORBENT GLASS MAT (AGM)** AGM batteries are constructed with a layer of glass mat sandwiched between the cells. This layer holds the electrolyte in place so the plates are permanently immersed, making the battery more efficient. Now effectively the standard replacement battery for motorcycle use.

**Pros** All the advantages of SLA, plus they are less prone to sulfation (see right) and can be stored for longer periods without needing to be charged. Vibration resistance makes them ideal for motorcycle use.AGMs also accept a faster charge rate than a than a conventional SLA battery and are more tolerant to deep discharge.

**Cons** Higher cost than basic LA types.

Lithium battery cells have a nominal voltage of 3.2v and four are arranged in series to create a 12.8v battery.

**Pros** High energy to weight ratio (up to four times greater than an LA) which means lithium batteries are much lighter than equivalent lead acid batteries. More starting power than a lead acid. No leakage. Fast charging capability.

**Cons** High cost. Lithium batteries are intolerant of over and undercharging, either of which causes damage. Also less tolerant of cold than a conventional LA. They absorb heat faster than other types, which can lead to premature failure if sited in a hot environment. Lithium batteries need an inbuilt battery management system (BMS) to protect each cell from excessive voltage during charging, overheating and over current during discharging. In worst case scenarios, lithium batteries can explode or catch fire if the charger isn’t properly regulated. Confirm any lithium battery has aBMS and only buy from reputable suppliers.

Absorbent Glass Mat battery features electrolyteimpregnated mat beween the lead plates, and a safety valve to release any excess pressure. There’s no need for a translucent case, because there is no need to check the level of acid in the battery.

There are two commonly used methods of rating a battery’s output; the amp-hour (Ah) rating quantifies the amount of power a battery can be expected to deliver over a specified time, operating in a temperature of 25°C. Abattery rated at 10Ah should deliver one amp for 10 hours (or two amps for five hours) without recharging.

The other method of rating output is to quote the cold cranking amps (CCA). This tells you how much current a fully charged 12v battery will deliver for 30 seconds at -18°C, while maintaining voltage above a specified threshold. A high quality 10Ah battery might have a CCA rating of 180amps. CCA ratings are particularly relevant for electric start bikes with high compression/large capacity.

Battery code numbers such as YTX12BS or YB7-A mainly relate to the battery’s dimensions. Ideally, use the battery code specified by the bike’s manufacturer unless your battery supplier will guarantee that an alternative code will fit.

Battery life is dictated by sulfation and ‘shedding’. Shedding is the unavoidable result of the plates expanding and contracting during the charging and discharging process, shedding small particles off the plates. A decent quality battery will have a life expectancy of approximately 500 charge/discharge cycles, ie typically 500 days of use.

Sulfation is the process in which small crystals of sulfate in electrolyte attach themselves to the plates. In normal cycles of use, the crystals detach themselves (smart chargers recreate these conditions to prolong battery life). But if the battery is left discharged, the crystals can permanently attach to the plates, acting as a barrier, preventing electrolyte from saturating the plates and thereby making the battery less efficient.

A completely discharged battery is unlikely to recover, so disconnect the battery if the bike is parked for over two weeks. Ideally, a battery should have 12.7-12.8v when stored and, to prevent condensation leading to internal corrosion, shouldn’t be stored in the cold, and especially not on a concrete floor. If you don’t want to leave the battery in situ on the bike, store it somehwere dry, well ventilated and away from draughts.

If, after a couple of months, the voltage drops to 12.5v or less, recharge it; 12.4v is approximately 60% charged, normal on a vehicle too low for long-term storage.

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Mike describes was the mind-expanding experience of racing the hills on a 350 Velocette on dope

Somewhere in the middle of gnarly Somerset, Patrick turned the Transit van off a B-road and squeezed it between the hedges of a narrow lane. “Is this the approach road to the hill?” I said. “No,” he said. “This is the hill.” In the paddock we unloaded the bikes from the van – Patrick’s 750cc Norton Commando, my 350cc Velocette MAC – and prepared for the day’s action. We would get a couple of practice runs and two or three competition dashes up the hill. I forget its name, but it was probably a typical 1000-yarder, and part of it ran between farm buildings. The marshals had to clean the cow pats off the road before the bikes could start running.

I’d bought the MAC – a pushrod twovalve single based on Velocette’s post-war road bike – for £250. I’d been hanging around the west country hillclimb scene for a while in the mid-’70s when Peter Isaac (who was, and still is, secretary of the hillclimb club, nhca.co.uk) said:

“Why don’t you have a go? Adrian Kessell is selling one of his grasstrack bikes – perfect for the hills.”

Adrian Kessell was a top name in Cornish grasstracking, and had been running the MAC on methanol, a fuel that gives a really fat midrange punch. The Velo had been set up for sliding around the left-hand corners of grass tracks, but it also worked perfectly well on the lefts and rights of a surfaced hill.

It’s best to have a target if you’re going racing. I was never going to be in contention for wins, but I always wanted to beat a pair of Morini V-twins that used to appear in the 350cc class. Frankly, I couldn’t imagine anything less appropriate for a nadgery hillclimb course than a 9000rpm redline. The Velo would long have spaghetti’d its valves at that rate.

The Morinis might have had the advantage on the long, power-sapping straight between the Sawbench and Martini hairpins at the 1000-yard Wiscombe Park climb in east Devon, but the way the dope-fuelled MAC spat out of hairpins often made it a better bike on the twistier courses. It was all good-natured, and the Morini guys no doubt enjoyed the challenge of their hi-tech Italian kit as much as I did my agricultural Velo.

Hillclimb racing is famous for its specials and, in those days, for wild-riding Cornishmen. Legendary hillclimbers such as Roy Opie and his 650cc Ariel-Triumph, and Paul Spargo with his 740cc Ariel- Triumph (the Ariel frame gave a low seating position) sometimes used hedges as a kind of wall-of-death springboard onto the following straight. A Midlands rider named Phil Gregory even constructed his own 1000cc V-twin special, based on two Jawa speedway engines, purely for our little enclosed world of the hills.

The most sublime hillclimb special that I’ve ever seen was the 500cc Velocette ridden by Peter Isaac himself. Some motorcycles talk speed, balance and perfection even when they’re leaning on a jerrycan, and this Velo did. It had narrow, flat handlebars and a lovely little polished-ally sprint tank atop the Venom engine.

If you want to perfect your riding technique, I would recommend hillclimb racing. A run might last only 40 seconds, so you can’t get a single corner wrong. But you have only half-a-dozen corners in which to prove yourself – you have to give it eleven-tenths.

Hillclimbing teaches you how to get the power on early from corner exits, and how to focus. It’s a bit like a MotoGP rider attempting a banzai qualifying lap, except that you’ll wrap yourself into a hedge or a tree, or sail out into a Cotswold valley (as at Prescott) if you get it wrong.

The Velo was leaning on a wall outside my garage one day. A car stopped and a man got out. “What is it?” he said. I told him. “£100?” he offered. The forks were knackered and the Velo really needed attention. The next day he came with a van and took it away.

From £250 to £100 in six months. I might have learnt a bit about hill climbing, but I’ve never learnt how to haggle.

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#### The conventional roller chain has largely been superseded by sealed-ring designs on modern bikes, but should we be fitting them to classics too?

Illustration **REGINA INTERNATIONAL LTD** Photo **JAQUES PORTAL**

‘I won’t skimp on chains, because the cheap stuff soon stretches and sags – particularly if you like to hammer on and off the throttle and you’re a bit shy with the chain lube.’

The standard roller chain, consisting of basic links with pins and rollers, was original fitment to older classics. A roller link is composed of two sideplates with hollow bushes pressed into them and a roller that’s free to rotate on each of those bushes. A pin link has pins pressed into sideplates; these connect the hollow links with the pins passing through the bushes in the roller links. The pins rotate in the bushes and the rollers spin on the bushes.

There are also solid impregnated roller chains in which the roller and bush are combined into a single fixed piece and the pin links rotate within them; the chain lube or oil lubricates the gap between pin and bush. Us older riders remember heating a tin of lube on the stove to immerse chains in, while mother/the other half was out. We also remember when chains seemed to need adjustment every week.

**\+ Pros** Cheap to manufacture and hence cheaper to buy. Lighter and less bulky than O-, X- and Z-ring types.

**\- Cons** Need more frequent oiling than sealed types. Dirt and grit can wheedle its way into links to form a grinding paste with oil and lube.

The O-ring chain was invented in the 1970s and became common fitment to motorcycles the following decade. The basic construction of sealing ring chain is like that of a standard roller chain, but with the addition of seals between the roller links and the sideplates of the pin links. These seals serve the dual purposes of containing the lubricant that’s injected between the pins and bushes when the chain is manufactured, and keeping dirt and moisture out when in service.

X-section rings were an evolution of the O-ring, intended to reduce drag and improve sealing. Z-ring is a further evolution by Regina. The O-ring has a single, wide sealing face on each side once squeezed between the roller and pin links. Later versions are designed to provide a better seal, to keep grease in and cack out, while also reducing friction, which can be significant.

**\+ Pros** Longer life and less frequent lubrication and adjustment required, if quality material and construction is used.

**\- Cons** Heavier, wider and more expensive than standard roller link chains. Needs a special tool for fitting the rivetted link, although some can use a spring link.

Roller chains are one of the few things that are still produced to imperial measurements, but with a simple three digit code to specify the size: 428, 520, 525 and 530 are the most common.

The first number denotes the pitch of the chain – the distance between the centres of neighbouring pins – and if that distance is ⅝in that number would be ‘5’ (if it were a ‘4’, that would be 4 /8 or ½in; a ‘6’ is 6 /8 or ¾in.)

The next two digits are the measure of the width of the rollers, in that most convenient of measures – eightieths of an inch. So ‘20’ is20 /80in or ¼in. A 520 chain would originally have been specified as5 /8in x ¼in.

If we were referring to a chain with ‘25’ as the second pair of digits, we’d be looking at25 /80in or5 /16in; ‘30’ would mean30 /80in or ⅜in.

It sort of makes sense – imagine how small the print on the sideplates would be if that lot were expressed in millimetres. Although 428 doesn’t quite work with the fractions of 80ths, so we’ll gloss over that.

Quality modern chains are remarkable, with 150bhp bikes needing minimal adjustment over thousands of miles. Price apart, fitting a chain with sealing rings looks like a no brainer, but be careful.

Their design makes them wider, which can present issues if retro-fitting to an older classic. Sideplates can vary from 1.5 to 2.6mm, depending on duty type and manufacturer, plus the additional width of the sealing rings. However, modern materials and construction mean that, if sprockets are available, you can often run a narrower chain than the original fitment. The power of most bikes specified with a 530 chain in the 1970s can easily be handled by a modern 520 O-ring.

It is also possible to use O-ring chains on the primary drive of some older classics. This allows the chain case to be run dry, with occasional spray lubrication, eliminating oil bath leaks. However, O-ring chains run hotter than standard chains, so with no oil to aid cooling that may be an issue – as well as clearance and lack of oil to the clutch bearing.

Also, some older bikes require chains with an uneven number of links (some Triumph T140s are 107 links). These require a cranked link, something only easily available for standard chain.

Simple: keep it clean, correctly adjusted and lubricated. Go for quality over low price and replace chain and sprockets as a set. Gearbox and rear sprockets must be in line – wear on a sprocket’s face can suggest an alignment issue.

Correct adjustment is vital for longevity. Measure free-play in the chain with the suspension loaded unless the manual states otherwise – and check with the wheel at different points of its rotation in case there are tight spots.

Double check free-play once you have re-tightened the wheel spindle, as sometimes a swingarm can open outwards when the spindle is loose, causing the chain to tighten when it’s done up. An over-tight chain will prevent the suspension from working properly, damaging gearbox output and wheel bearings. Too loose can cause vibration or even jumping.

O-ring chains are less fussy about lubrication than conventional items, with most people opting for the convenience of an aerosol chain lube, the majority of which are O-ring safe (but check). Lube has more to do on a standard chain, where it needs to get into the links.

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