Dellorto PHM 40
Large Dell'Orto range with accelerator pump; jet needles of the K series.
Fitted as standard to
All figures at a glance (table)
| Model | Year | Main jet | Pilot jet | Starter jet | Needle (clip) | Atomiser | Slide |
|---|---|---|---|---|---|---|---|
| Moto Guzzi Le Mans 3 – PHM 40 | 1982 | 170 | 60 | – | K 4 (2) | 265 AB | 601 |
| Moto Guzzi Le Mans 4 (Germany / Austria) | 1988 | 145 | 57 | 60 | K 19 (3) | 266 AB | 605 |
| Moto Guzzi Le Mans 4 (Italy) | 1988 | 145 | 57 | 60 | K 19 (3) | 268 AB | 605 |
| Moto Guzzi Le Mans 4 | 1984 | 145 | 57 | 60 | K 19 (3) | 268 AB | 605 |
| Moto Guzzi Le Mans 4 (USA) | 1985 | 150 | 62 | 60 | K 33 (3) | 260 AB1 | 503 |
| Moto Guzzi 1100 Sport (USA) | 1994 | 152 | 52 | 60 | K27 (2) | 265 AB1 | 503 |
| Moto Guzzi 1100 Sport | 1994 | 152 | 57 | 60 | K18 (3) | 266 AB | 605 |
| Ducati 900 SS Replica (Mike Hailwood Replica) – left carburettor (BS) | 1981 | 140 | 65 | 60 | K 5 (2) | 265 AB | 60/1 |
| Ducati 900 SS Replica (Mike Hailwood Replica) – right carburettor (BD) | 1981 | 135 | 65 | 60 | K 5 (2) | 265 AB | 60/1 |
| Ducati 900 S2 | 1982 | 135 | 65 | 60 | K 5 (2) | 265 AB | 60/1 |
| Ducati 1000 Replica (Mille MHR) | 1984 | 125 | 65 | 60 | K 5 (2) | 265 AB | 60/1 |
| Ducati 750 F1 Montjuich – left carburettor (NS) | 1986 | 155 | 65 | 60 | K 5 (2) | 265 AB | 60/1 |
| Ducati 750 F1 Montjuich – right carburettor (ND) | 1986 | 148 | 65 | 60 | K 5 (2) | 265 AB | 60/1 |
| KTM 600 Incas | 1989 | 195 | – | 45 | K 51 (2) | 272 DR | 40 |
| Model | Moto Guzzi Le Mans 3 – PHM 40 | Moto Guzzi Le Mans 4 (Germany / Austria) | Moto Guzzi Le Mans 4 (Italy) | Moto Guzzi Le Mans 4 | Moto Guzzi Le Mans 4 (USA) | Moto Guzzi 1100 Sport (USA) | Moto Guzzi 1100 Sport | Ducati 900 SS Replica (Mike Hailwood Replica) – left carburettor (BS) | Ducati 900 SS Replica (Mike Hailwood Replica) – right carburettor (BD) | Ducati 900 S2 | Ducati 1000 Replica (Mille MHR) | Ducati 750 F1 Montjuich – left carburettor (NS) | Ducati 750 F1 Montjuich – right carburettor (ND) | KTM 600 Incas |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Year | 1982 | 1988 | 1988 | 1984 | 1985 | 1994 | 1994 | 1981 | 1981 | 1982 | 1984 | 1986 | 1986 | 1989 |
| Main jet | 170 | 145 | 145 | 145 | 150 | 152 | 152 | 140 | 135 | 135 | 125 | 155 | 148 | 195 |
| Pilot jet | 60 | 57 | 57 | 57 | 62 | 52 | 57 | 65 | 65 | 65 | 65 | 65 | 65 | – |
| Starter jet | – | 60 | 60 | 60 | 60 | 60 | 60 | 60 | 60 | 60 | 60 | 60 | 60 | 45 |
| Needle (clip) | K 4 (2) | K 19 (3) | K 19 (3) | K 19 (3) | K 33 (3) | K27 (2) | K18 (3) | K 5 (2) | K 5 (2) | K 5 (2) | K 5 (2) | K 5 (2) | K 5 (2) | K 51 (2) |
| Atomiser | 265 AB | 266 AB | 268 AB | 268 AB | 260 AB1 | 265 AB1 | 266 AB | 265 AB | 265 AB | 265 AB | 265 AB | 265 AB | 265 AB | 272 DR |
| Slide | 601 | 605 | 605 | 605 | 503 | 503 | 605 | 60/1 | 60/1 | 60/1 | 60/1 | 60/1 | 60/1 | 40 |
“–” means: not fitted on this model, or not documented in the source.
Not running right?Pick the symptom, we show the part responsible.
Pale, greyish-white plugs; flat and gutless at the top end; overheating
Runs better on choke; popping/banging on the overrun
Hesitation/flat spot when opening the throttle
Surging/leaning out at steady speed and mid throttle
Sooty black plugs; burbling running; smell of fuel; high consumption
Gets worse the hotter the engine runs
Always change in single steps (“one or two jet sizes, then check the plug colour”), judge only on a warmed-up engine and make just one change per test ride.
These notes do not replace a proper check. When in doubt use a lambda meter, a dyno or a specialist workshop – an engine running lean for long periods can be damaged.
More spare parts for Dell'Orto PHM
Real-world setups from the community
Documented setups from forums, summarised in our own words and linked. They show what people actually ran on specific conversions – they are not a recommendation and do not replace your own testing.
User report, no warranty — not a factory figure
Moto Guzzi 1000 S — PHM 40
Condition/modifications: Standard airbox, twin-plug ignition
Jetting used: Main jet 155, pilot jet 55, throttle slide 60, atomiser and needle standard
Result according to the report: User reports unremarkable running, consumption around 4.3 l/100 km, normal engine temperatures (90–100 °C oil).
Source: groups.google.com
Further reading
Frequently asked questions
What does the atomiser do and why does it matter so much?
The atomiser (also called the needle jet or emulsion tube) is the sleeve the jet needle runs in. Together with the needle it governs the mixture in the part-throttle range — exactly where you ride almost all the time. Experienced tuners rate it at least as important as the main jet: a single step (say 262 to 264) changes how the bike rides noticeably. With Dell'Orto the number is the bore and the letters are the design (e.g. AB, AR).
Discussion: caferacer-de
What does the needle clip position do?
The needle hangs from the throttle slide and its taper opens up the cross-section in the atomiser. Move the clip one notch down (needle sits higher) and the part-throttle range gets richer, one notch up (needle lower) leans it out. The factory figure counts the notches from the top. The needle position acts roughly between 1/4 and 3/4 throttle — not at idle and barely at full throttle.
Discussion: caferacer-de
How do I set the mixture screw correctly?
As a starting point the Moto Guzzi workshop manuals for the carburettor models consistently give 1.5 turns out from lightly seated. Fine tuning on a warmed-up engine: turn the mixture screw on each cylinder slowly until the engine runs at its smoothest and fastest, then correct the idle speed and synchronise both carburettors. If the engine only runs cleanly at well over two turns, the pilot jet is usually too small or the circuit is dirty.
Discussion: 2-ventiler.de
The engine hesitates when I open the throttle — why?
When the slide is opened quickly the mixture leans out briefly. PHF and PHM have an accelerator pump for exactly that — if the engine hesitates, its pump jet is often blocked, the diaphragm is damaged, or the idle-to-needle transition is too lean. On carburettors without a pump (e.g. VHB, PHBH) only a clean transition setup helps. Check the mundane causes too: float level, fuel supply, worn slides.
Discussion: 2-ventiler.de
Do both carburettors need the same jetting?
Yes. Both cylinders need the same set of jets, and the factory figures always apply per carburettor. After every job the pair belongs synchronised (same slide lift, same mixture screw setting), otherwise one cylinder runs richer than the other and the plug colour becomes unreadable. Unequal jetting is almost always a sign of a previous owner tinkering.
Discussion: 2-ventiler.de