GOSFIELD ENGINEERING, Melbourne (2026)

09/09/2026

If you write or design for whatever reason you’ll be glad you bought a copy of David Whitbread’s “The Design Manual”. Just by fanning though it you’ll learn how to structure a document.

If you actually read it, you will win BIG and be glad you did. It’s comprehensive, logical, smart and easy. The revised and encyclopaedic third edition is available now.

23/04/2026

AUSSIE DUST: THE ENGINE KILLER.

The facts about air filters and Australian dust.

If you own an adventure bike in Australia and ride it off-road, you need to know that the original paper element air filters fitted at the factory by most European manufacturers will not keep fine Australian dust out of your engine.

The land surface in Australia is the oldest on earth, with an average age of over two billion years. Large parts of the Australian land surface are well over four billion years old. The result of all these billions of years of weathering is dust particles so fine that they easily pass through most types of OEM and aftermarket air filters.

Worse of all are the aftermarket filters that “claim” to increase engine performance by increasing air flow. These are particularly useless at filtering dust. The worst offenders are the ones made of cotton fabric enclosed in corrugated steel mesh. There are lots of them on the market now, and unfortunately, the most significant “increase” achieved with any of them is not engine performance; it’s engine wear.

The only filter type to adequately filter very fine dust is a good-quality oiled foam one. The types of foam used to make proper automotive air filters are Open-Cell Reticulated Polyurethane or Polyester. These types of foam allow high airflow through an internal matrix that catches and traps even the smallest dust particles on the oiled surfaces throughout the entire depth of the foam, not just the outer surface.

Although the main dust risk is for bikes of any type that travel on dirt roads, even the odd exposure to road works can cause your road bike engine to breathe in a bit of dust, and I’ve seen fine dust in plenty of road bike airboxes before.

Unifilter Australia make foam air filters for a large number of makes and models, including specific replacements for Aprilia and Moto Guzzi. A notable example is Unifilter AU 6901ST designed for the V85 TT to replace the OEM paper element filter AP8104329, which, like all of them, lets through fine dust. As it happens, AP8104329 is also the standard filter for over ten other Aprilia and Guzzi models, giving a lot more owners the option of keeping out the killer dust. The following lists the models that use the standard air filter AP8104329.

Aprilia Off-Road Bikes:
RXV & SXV 450-550 2006-2011

Aprilia V-Twin Road/Sports Bikes:
RSV 1000 2004-2008
Tuono 1000 2006-2009

Aprilia V-Four Road/Sports Bikes:
RSV4 1000 2011-2014
Tuono 1000 2011-2015
Tuono 1100 2015-2026

Moto Guzzi Adventure Bikes:
V85 TT 2019-2027
Stelvio 1200 2008-2017

Moto Guzzi Road Bikes:
Griso 850/1100/1200 2005-2017
California 1400 All variants (Audace/Custom/Touring/Eldorado/MG-X21) 2012-2021

19/01/2026

THE FACTS ABOUT SECONDARY AIR INJECTION

The internet is awash with misinformation on just about every subject, and Motorcycle Secondary Air Injection (SAI) is no exception.

SAI is one of the most misunderstood systems in modern motorcycle engineering. Its sole purpose is to add small amounts of air to the engine exhaust just as it enters the header pipes. The injection only occurs under pre-determined conditions, typically when the throttles are closed at start-up and on cold idle when the fuel mixture is intentionally rich. The additional air simply allows any excess fuel vapour in the exhaust to oxidise before exiting the system.

SAI has no detrimental effect whatsoever on performance and does not harm the engine in any way. The amount of air is very small, does NOT enter the engine cylinders or become part of the internal combustion process. SAI does NOT create a lean condition or make the exhaust valves overheat.

Unlike secondary air systems on some car engines, motorcycle secondary air does not employ pumps or complicated plumbing, and in fact, the air is not even “injected”. Motorcycle systems use a simple solenoid valve controlled by the ECU and passive reed valves to draw air in through tiny holes in the outer part of the exhaust ports, typically just where the headers are bolted on.

All naturally aspirated engines create a naturally occurring negative pressure pulse in the exhaust whenever the throttles are closed. Motorcycle SAI takes advantage of this by opening the solenoid valve and allowing the reed valves to open and pass a small amount of air.

This can only occur when the throttles are closed, and even then, only if the ECU allows it by opening the solenoid valve. The reed valves stay closed at all other times, and no additional air enters the exhaust.

FACT: Secondary air can only be drawn into the exhaust when the throttles are closed, and only if the ECU allows the solenoid valve to open.

FACT: Secondary air does not add air to the combustion chamber or have any effect whatsoever on the fuel mixture.

FACT: A motorcycle secondary air solenoid valve is not a pump. It is simply a normally closed valve that the ECU can open if required.

The image here shows the secondary air path on a Moto Guzzi V85. If the solenoid valve opens and the throttle is closed, air can be drawn from the airbox through the reed valves on the side of the cylinder heads. Small holes drilled through the heads (shown by the light blue arrows) take air from below the reed valves directly to the exhaust ports just near the point where the exhaust enters the pipes.

16/01/2026

PUMP PETROL, WHAT’S THE DIFFERENCE?

NOTE:........ We recommend reading the previous post about octane ratings first.

Petrol is sold with different octane ratings because not all petrol engines are the same, and different engines need different petrol.

91 RON is suitable for engines in many general-purpose, everyday road cars and some older classic motorcycles.

95 RON is required for a range of higher-performance engines used in modern motorcycles and prestige road cars.

98 RON is required for modern high-performance sports cars and motorcycles, or those with modified engines. 98 RON is also required for many older air-cooled motorcycle engines with conventional fuel and ignition systems and unfavourable combustion chamber characteristics.

WHICH ONE FOR MY BIKE? :
The first place to look for the correct petrol octane rating for your bike is your owner’s manual. Never use fuel with an octane rating below the manufacturer's minimum specification. You can, however, use petrol with a higher octane rating without any problem.

Compression ratio:
While an engine's compression ratio is one of the factors to be considered, it is not the only one by any means. Engine type, combustion chamber size and shape and fuel and ignition systems are equally important.

Operating temperature:
Air-cooled engines run hotter than liquid-cooled engines and, as a result, are at higher risk of detonation due to high and/or unstable engine temperature.

Cylinder displacement:
Large capacity engines with fewer cylinders are at higher risk of detonation due to their large displacement per cylinder, which can promote uneven combustion.

Combustion chamber design:
Engines with offset single spark plugs and unfavourable combustion chamber shapes are also subject to uneven combustion and are at higher risk of detonation.

Fuel systems:
Carburettored engines are at higher risk of detonation than modern fuel-injected engines, as carburettors cannot accurately control air/fuel mixture. Uneven intake pressures and/or fuel starvation are immediate causes, while constant over-fuelling builds carbon deposits which impede heat transfer, making the engine run hotter and creating hot spots on combustion chamber surfaces.

Ignition systems:
Old-fashioned contact breaker ignition systems with mechanical advance mechanisms are unable to control ignition timing accurately and are often poorly maintained and/or incorrectly set up. Incorrect ignition timing is a major cause of serious detonation and engine damage.

OLD BIKE or NEW BIKE?
EXAMPLE 1: Current model 1100cc Aprilia V4 and 1046cc Moto Guzzi V100 engines have compression ratios of 13.6:1 and 12.6:1, respectively, yet both these bikes have a factory-specified minimum fuel octane rating of 95 RON.

EXAMPLE 2: A 1977 844cc Moto Guzzi T3 engine has a compression ratio of 9.5:1 and a factory-specified minimum fuel octane rating of 98 RON.

Both bikes in the first example have liquid-cooled engines with four-valve heads, well-proportioned combustion chambers with centre spark plugs and very sophisticated digital fuel injection and ignition systems. Although they are, by definition, high-compression engines, their modern design allows them to safely run on mid-range premium fuel.

The bike in the second example has an air-cooled engine with two-valve heads and an offset spark plug in a less-than-ideally shaped combustion chamber, with fuel delivery through gravity-fed carburettors and mechanical points ignition set at an extremely high angle to compensate for the offset plug and unfavourable combustion chamber shape. Despite being a relatively low-compression engine, the shortcomings of some elements of the design mean that high-octane fuel is needed to avoid potentially damaging engine knock.

The point here is that high-octane fuel is not just for supercars and superbikes; it’s also needed to protect certain older engine types and is actually what was originally specified for them when they were first designed and built.

GUZZI OWNERS should be aware that the equivalent of 98 octane RON is the factory’s published fuel specification for every V-twin with carburettors made since the original 1967 V7 700. This equates to the old leaded petrol known as “Four-Star” in Europe or “Super” in Australia, and is still the correct specification for every carby Guzzi, both big block and small block and all the variants.

Even back then, Australian petrol octane levels were the same as those in Europe. The octane rating of “Super” sold at stations throughout Australia was between 98 and 100 RON. The old “Standard” petrol from the same era was between 90 and 92 RON.

Early factory manuals and documentation sometimes used different labels such as “NO”, “NO-RM” or “NORM” to describe ocatane howver these designations are the same as the current-day RON scale. E.g. 98 NO-RM or 98 NORM is the same as 98 RON.

16/01/2026

PETROL OCTANE RATINGS, WHAT ARE THEY REALLY?

Octane ratings are a measure, or “score,” of how well different fuels resist the potentially damaging phenomenon known as “detonation” or “engine knock”. Detonation occurs when the air/fuel mixture in an engine cylinder explodes prematurely, instead of burning in a controlled manner at the correct point in the cycle. When detonation occurs, a pronounced “pinging” or “knocking” sound can be heard coming directly from the engine. Using fuel with an octane rating lower than what an engine requires is a primary cause of detonation and the damage that follows.

The scale used to classify petrol octane in Australia is the RON (Research Octane Number) scale. The RON scale is also used in all of Europe, New Zealand, the UK, most of Asia, Africa, South America and the Middle East. Ratings given at fuel bowsers in the above regions are the same as they are here.

The United States, Canada, Mexico and Brazil do not use the RON scale and any online content or information about fuel octane coming from those countries, or any location where it is not certain that RON is the scale being referenced, is irrelevant to Australia and must be ignored.

The National Measurement Institute tests all fuel sold at petrol stations in Australia for quality and octane rating by chemical analysis and using a special test engine that compares the fuel’s “knock resistance” against two benchmark hydrocarbon compounds.

The lowest octane fuel sold in Australia is 91 RON standard unleaded. The next level is 95 RON premium unleaded. The highest octane petrol generally available at petrol stations in Australia is 98 RON premium unleaded.

High-octane petrol does not increase engine power by itself. It is simply more stable under pressure, allowing highly tuned or modern high-compression, turbo and supercharged engines to achieve higher performance without the risk of damage caused by detonation.

Using higher octane petrol than your engine needs will not harm the engine in any way. It will just mean you will be paying more for fuel with little or no tangible benefit.

Using lower octane petrol than your engine needs will definitely harm the engine and even cause sudden catastrophic failure.

The primary causes of detonation are:
1 - Fuel with an octane rating too low for the engine type or state of tune.
2 - Excessive engine temperature.
3 - Overly lean air-fuel mixture.
4 - Poorly maintained engines with unbalanced intakes or incorrect ignition timing.
5 - Carbon build-up in the combustion chamber due to an overly rich fuel mixture or engine wear.

14/01/2026

SERVICE FLUID NOTES

ENGINE OIL:
All air-cooled Moto Guzzi engines, the Aprilia RXV & SXV engines and all scooter engines have separate transmission housings that do not share oil with the engine or use the engine oil to lubricate the clutch. While all these engines can use motorcycle-specific oil, they can also use oil designed for other petrol engine types, including cars, provided it is full synthetic and of the correct grade. These engines are tagged with an asterisk (*) in the service fluid table in an earlier post.

All other Aprilia motorcycle engines and the new Moto Guzzi V100 engine share the engine oil with the gearbox and clutch. These engines MUST use motorcycle-specific oil. Many modern car oils contain friction modifiers that can cause motorcycle clutches to slip and even damage some transmission components. The factory specifies oil that meets the JASO MA or JASO MA2 standards. The Japanese Automotive Standards Organisation developed JASO MA for modern motorcycle engines in the late 1990s with a formula designed to properly lubricate highly loaded gears without causing clutches to slip. This oil type is often labelled “4T”, but JASO MA or JASO MA2 needs to be on the label for it to comply.

ENGINE OIL FOR AIR COOLED GUZZI V-TWINS:
10W-60 API SL full synthetic engine oil is now recommended across the board for all air-cooled Guzzi V-Twins. This includes every big-block and small-block model from 1967 until the introduction of the V100 in 2022. The oil specified for the earliest loop frame V-Twins and the Daytona was 20W-50. 10W-50 full synthetic was specified for all Tonti frame and small-block models. 10W-60 API SL full synthetic now supersedes all those grades. The only exceptions are the few California models with hydraulic tappets built between 2003 and 2005. 5W-40 API SL full synthetic is recommended for these engines.

GEAR OIL:
Synthetic gear oil is now widely available and, where specified, should be used. Synthetic gear oil wasn’t specified for earlier models, but can be used without any problem, provided it is of the correct grade. The upper viscosity number, typically 90 or 140, should be strictly followed. The lower number, typically 75W, 80W or 85W is interchangeable; for example, 80W can be substituted for 75W and 85W. NEVER put additives in gear oil. Although molybdenum disulphide-based additives were recommended in service schedules from forty or fifty years ago (probably when oil was less sophisticated). The factory now categorically states that additives must not be used.

BRAKE FLUID:
Use only DOT 4 or DOT 5.1 brake fluid in braking systems and hydraulic clutches. Both are cross-compatible, meaning one can be topped up with the other if necessary. DOT 5.1 has a slightly higher boiling point than DOT 4 and is recommended for high-performance sports bike brakes and hydraulic clutches.
NEVER USE DOT 5 BRAKE FLUID! DOT 5 is not compatible with DOT 4 or DOT 5.1 AND WILL DAMAGE BRAKE SYSTEMS NOT DESIGNED FOR IT.

ENGINE COOLANT:
Type A, Red OAT (Organic Acid Technology) ethylene glycol coolant to Italian industry specification CUNA NC 956-16 is required for all liquid-cooled Piaggio Group engines. Some early Aprilia documents specified IP Ecoblu, a blue coloured variant, or red Permanent Spezial. Both of these conform to the CUNA standard; however, these days, the correct grade is likely to be red or pink. Never use green coolant in Piaggio Group engines or mix coolants of different types or colours. Only use Type A, ethylene glycol OAT coolants that comply with CUNA NC 956-16.

FORK OIL:
Fork oil is hydraulic oil that typically comes in viscosity ratings from 0W to 20W. ATF (automatic transmission fluid) is also hydraulic oil and can be substituted for fork oil. ATF viscosity is around 10W and is a valid alternative to fluids specifically labelled as fork oil.

14/01/2026

Official service fluid specs. for Aprilia, Guzzi and Piaggio Group vehicles.

13/01/2026

GUZZI V100 ENGINE

Moto Guzzi's first liquid-cooled twin overhead cam production bike has an engine unlike any other Guzzi or any other bike, for that matter. While overhead cams and liquid cooling have been part of Guzzi’s rich factory racing history. The V100 is the first liquid-cooled DOHC production bike to come out of the Mandello factory. One of the many features new to the V100 engine is the use of “finger” cam followers. Finger followers have been around in various forms for decades, first coming to prominence in Japanese factory racing engines. They were less common in the past, but due to improvements in materials science and manufacturing technology, they are becoming more common in high-end European and Japanese motorcycle engines.

By definition, DOHC (Dual Over-Head Cam) engines have individual inlet and exhaust cams positioned directly above the valves, most commonly with inverted cylindrical cups or “buckets” on top of each valve stem. The cam lobes act directly on the buckets, which slide in bores concentric with the valve. Clearance adjustment shims are placed under the buckets.

Finger follower systems utilise small pivot beams, or “fingers,” on a fixed rod or pin rather than buckets as described above. An adjustment shim sits under each finger on top of the valve stem, enclosed by the spring retainer. Finger follower systems have significant advantages over conventional bucket followers. They are more compact, have lower reciprocating mass and provide mechanical advantages that translate directly into better engine performance.

This rear-view cross-section of a V100 Cylinder Head shows how the fingers sit between the cam lobes and valve stems. Note the unusual shape of the cam lobes compared to cams made for conventional followers.

In addition to timing the opening and closing sequence, the shape or “profile” of cam lobes affect two critical performance factors:

1 - Duration - (the amount of time the valves open).
2 - Lift - (how far the valves open).

In general terms, a shorter duration improves low and mid-range torque, while more lift improves top-end power. Conventional cam and follower systems are limited in their ability to optimise both duration and lift, and always end up compromising in one or the other direction.

The inherent mechanical advantages of finger follower systems, on the other hand, support much higher opening speeds, allowing the use of cam profiles that have both high lift and short duration. The result is an engine capable of producing excellent low-end torque without compromising top-end power.

The reduced reciprocating mass of finger followers compared to conventional bucket followers also allows for increased maximum engine speed without the occurrence of valve flutter. More speed without uncontrolled valve movement always = more power.

13/01/2026

FUEL- Ethanol and E10 - DON'T GET IT WRONG!

This post deals with ethanol content in Australian fuel and why some bikes started to appear with little round E5 and E10 stickers on their fuel tanks. There’s a fuller explanation for the stickers below; however, for our purposes, all we need to know for now is that the stickers are only relevant in Europe, that Australian E10 is of a lower standard than in Europe and that local E10 should NOT be used in Piaggio Group bikes and scooters.
In Australia, E10 is just regular 91 octane petrol blended with “up to” 10% ethanol. While ethanol is a natural octane improver, even at the full 10%, it will not make 91 RON into 95 RON and may well be even less, as it is only “up to” and not standardised at the full amount.
E10 in Australia does not meet the minimum requirement for Piaggio Group bikes and scooters.
Even if local E10 was up to scratch, blended fuel has a number of disadvantages over normal petrol and many earlier Aprila and Moto Guzzi models, including some fuel-injected ones, are excluded from using blended fuel. The exclusion list is at the bottom of this page.
Problems with Ethanol:
Ethanol is hygroscopic, meaning that it absorbs water from the air.
Ethanol will corrode aluminium over time. The rate of corrosion increases as it absorbs more water, which then also corrodes ferrous metals.
Absorbed water can precipitate out of the fuel, causing contamination and further potential damage to the fuel system.
The fuel can separate or "split" if the bike is stored for more than a month or so. If this occurs, the ethanol component will evaporate more quickly than the remaining petrol, thereby reducing the octane rating of whatever is left.
Ethanol produces 30% less energy than petrol, so at 10% concentration, the engine will produce 3% less power while requiring 3% more fuel to maintain a correct air/fuel ratio.
NEVER put ethanol-blended fuel in a bike with carburettors or a steel fuel tank. Better still, just don't use it at all.
THE EXCLUSION LIST:
The following list was published by the factory some years back when ethanol-blended fuel started to become more prominent. These models are not approved for ethanol-blended fuel, despite most of them having fuel-injected engines. All other models that predate the list below or any model with a carburettor or a steel fuel tank should not use ethanol-blended fuel.
Aprilia:
- SL Falco 1000cc
- RSV 1000cc 1998 - 2003
- Tuono 1000cc 2002 - 2006
- Shiver 750cc
- RS 125cc
- RX / SX 125cc
- Pegaso (Rotax)
- RXV / SXV 450cc & 550cc
Moto Guzzi:
- V7 Classic: Before chassis ZGULW0001BM115002
- V7 Cafè: Before chassis ZGULWA006BM112067
- V7 Racer: Before chassis ZGULWB00XBM100722
- California 1100: other than chassis ZGUKDE, ZGUKDG, ZGUKDH, ZGUKDL, ZGUKDM
- Breva: 750
- Griso 850: Before chassis ZGULSB0016M111528
- Griso 1100: Before chassis ZGULS00017M1133321
- Griso 1200: Before chassis ZGULSE - ZGULSG
The explanation for why the little round stickers are there in the first place:
In 2018, the European Commission mandated new fuel standards and labelling for all retail fuel outlets, with corresponding labels to be applied to new vehicles. Motorcycles (that are actually made in Europe) then began to appear in other parts of the world, including Australia, with the little round E5 and E10 stickers on their fuel tanks. While the meaning of the stickers made sense to Europeans, they caused a lot of confusion among new bike owners and selling dealers outside the EU, where regulations require that the majority of petrol sold at retail outlets has some level of biofuel content. 95 octane RON unleaded petrol has been the base level in most of Europe for many years. It now contains 10% ethanol and is now simply referred to as E10. Premium grade petrol in Europe has always been 98 octane RON, now contains 5% ethanol and is simply referred to as E5. The two little stickers are there to advise owners that the bike can run on either 98 or 95 octane fuel, that 95 RON is the lowest allowable octane rating and that 10% is the maximum permitted amount of ethanol. Higher octane fuel rated at 100-102 RON without ethanol and known as Super Premium among other names, is also available for highly tuned or older cars and bikes that need to avoid ethanol.

GOSFIELD ENGINEERING

09/09/2026

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19/01/2026

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