Dell'Orto PHF 30 – jetting & tuning
Dell'Orto range with accelerator pump; jet needles of the K series. Fitted from the factory to 8 documented models from Ducati, Moto Guzzi; with accelerator pump (pump jet).
| Make | Model | Year | Version | Designation | Reg. no. | Details |
|---|---|---|---|---|---|---|
| Ducati | 350 Indiana | 1986 | carburettor reg. 4659 | PHF 30 DD | 4659 | view jetting |
| Ducati | 350 Indiana | 1986 | carburettor reg. 4660 | PHF 30 DD | 4660 | view jetting |
| Ducati | 350 XL | 1982 | left carburettor (BS) | PHF 30 BS | 4597 | view jetting |
| Ducati | 350 XL | 1982 | right carburettor (BD) | PHF 30 BD | 4598 | view jetting |
| Moto Guzzi | 1000 SP II | 1986 | Standard | PHF 30 DS/DD | 4661/62 | view jetting |
| Moto Guzzi | 1000 SP II | 1986 | USA / Switzerland | PHF 30 DS/DD | 4655/56 | view jetting |
| Moto Guzzi | 1000 SP II | 1988 | USA | PHF 30 DS/DD | 4674/75 | view jetting |
| Moto Guzzi | 1000 SP II | 1988 | USA | PHF 30 DS/DD | 4674/75 | view jetting |
| Moto Guzzi | 850 T5 | 1984 | Standard | PHF 30 DS/DD | 4621/22 | view jetting |
| Moto Guzzi | California 2 | 1986 | Standard | PHF 30 DS/DD | 4663/64 | view jetting |
| Moto Guzzi | California 3 | 1986 | Standard | PHF 30 DS/DD | 4667/68 | view jetting |
| Moto Guzzi | California 3 | 1988 | Germany / Austria | PHF 30 DS/DD | 4678/79 | view jetting |
| Moto Guzzi | California 3 | 1988 | USA | PHF 30 DS/DD | 4674/75 | view jetting |
| Moto Guzzi | California 3 | 1989 | Switzerland | PHF 30 DS/DD | 4682/83 | view jetting |
| Moto Guzzi | Mille GT | 1988 | USA | PHF 30 DS/DD | 4674/75 | view jetting |
| Moto Guzzi | Mille GT | 1988 | USA | PHF 30 DS/DD | 4674/75 | view jetting |
| Moto Guzzi | V1000 Convert | 1980 | Standard | PHF 30 DS/DD | 4566/67 | view jetting |
| Make | Ducati | Ducati | Ducati | Ducati | Moto Guzzi | Moto Guzzi | Moto Guzzi | Moto Guzzi | Moto Guzzi | Moto Guzzi | Moto Guzzi | Moto Guzzi | Moto Guzzi | Moto Guzzi | Moto Guzzi | Moto Guzzi | Moto Guzzi |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Model | 350 Indiana | 350 Indiana | 350 XL | 350 XL | 1000 SP II | 1000 SP II | 1000 SP II | 1000 SP II | 850 T5 | California 2 | California 3 | California 3 | California 3 | California 3 | Mille GT | Mille GT | V1000 Convert |
| Year | 1986 | 1986 | 1982 | 1982 | 1986 | 1986 | 1988 | 1988 | 1984 | 1986 | 1986 | 1988 | 1988 | 1989 | 1988 | 1988 | 1980 |
| Version | carburettor reg. 4659 | carburettor reg. 4660 | left carburettor (BS) | right carburettor (BD) | Standard | USA / Switzerland | USA | USA | Standard | Standard | Standard | Germany / Austria | USA | Switzerland | USA | USA | Standard |
| Designation | PHF 30 DD | PHF 30 DD | PHF 30 BS | PHF 30 BD | PHF 30 DS/DD | PHF 30 DS/DD | PHF 30 DS/DD | PHF 30 DS/DD | PHF 30 DS/DD | PHF 30 DS/DD | PHF 30 DS/DD | PHF 30 DS/DD | PHF 30 DS/DD | PHF 30 DS/DD | PHF 30 DS/DD | PHF 30 DS/DD | PHF 30 DS/DD |
| Reg. no. | 4659 | 4660 | 4597 | 4598 | 4661/62 | 4655/56 | 4674/75 | 4674/75 | 4621/22 | 4663/64 | 4667/68 | 4678/79 | 4674/75 | 4682/83 | 4674/75 | 4674/75 | 4566/67 |
| Details | view jetting | view jetting | view jetting | view jetting | view jetting | view jetting | view jetting | view jetting | view jetting | view jetting | view jetting | view jetting | view jetting | view jetting | view jetting | view jetting | view jetting |
| Model | Year | Main jet | Pilot jet | Starter jet | Needle (clip) | Atomiser | Slide |
|---|---|---|---|---|---|---|---|
| Ducati 350 Indiana – carburettor reg. 4659 | 1986 | 122 | 52 | 75 | K 2 (2) | 260 AB | 60/3 |
| Ducati 350 Indiana – carburettor reg. 4660 | 1986 | 118 | 52 | 75 | K 2 (2) | 260 AB | 60/3 |
| Ducati 350 XL – left carburettor (BS) | 1982 | 122 | 60 | 75 | K 2 (2) | 260 AB | 60/3 |
| Ducati 350 XL – right carburettor (BD) | 1982 | 118 | 60 | 75 | K 2 (2) | 260 AB | 60/3 |
| Moto Guzzi 1000 SP II | 1986 | 125 | 50 | 75 | K 23 (3) | 264 AB | 503 |
| Moto Guzzi 1000 SP II (USA / Switzerland) | 1986 | 135 | 48 | 75 | K 27 (2) | 261 AB1 | 503 |
| Moto Guzzi 1000 SP II (USA) | 1988 | 135 | 48 | 75 | K 27 (2) | 261 AB1 | 503 |
| Moto Guzzi 1000 SP II (USA) | 1988 | 135 | 48 | 75 | K 27 (2) | 261 AB1 | 503 |
| Moto Guzzi 850 T5 | 1984 | 130 | 50 | 75 | K 23 (3) | 264 AB | 503 |
| Moto Guzzi California 2 | 1986 | 125 | 50 | 75 | K 23 (3) | 264 AB | 503 |
| Moto Guzzi California 3 | 1986 | 125 | 50 | 75 | K 23 (3) | 264 AB | 503 |
| Moto Guzzi California 3 (Germany / Austria) | 1988 | 125 | 50 | 75 | K 23 (3) | 262 AB | 503 |
| Moto Guzzi California 3 (USA) | 1988 | 135 | 48 | 75 | K 27 (2) | 261 AB1 | 503 |
| Moto Guzzi California 3 (Switzerland) | 1989 | 125 | 48 | 75 | K 27 (3) | 261 AB1 | 503 |
| Moto Guzzi Mille GT (USA) | 1988 | 135 | 48 | 75 | K 27 (2) | 261 AB1 | 503 |
| Moto Guzzi Mille GT (USA) | 1988 | 135 | 48 | 75 | K 27 (2) | 261 AB1 | 503 |
| Moto Guzzi V1000 Convert | 1980 | 112 | 50 | 75 | K 27 (2) | 262 AB1 | 503 |
| Model | Ducati 350 Indiana – carburettor reg. 4659 | Ducati 350 Indiana – carburettor reg. 4660 | Ducati 350 XL – left carburettor (BS) | Ducati 350 XL – right carburettor (BD) | Moto Guzzi 1000 SP II | Moto Guzzi 1000 SP II (USA / Switzerland) | Moto Guzzi 1000 SP II (USA) | Moto Guzzi 1000 SP II (USA) | Moto Guzzi 850 T5 | Moto Guzzi California 2 | Moto Guzzi California 3 | Moto Guzzi California 3 (Germany / Austria) | Moto Guzzi California 3 (USA) | Moto Guzzi California 3 (Switzerland) | Moto Guzzi Mille GT (USA) | Moto Guzzi Mille GT (USA) | Moto Guzzi V1000 Convert |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Year | 1986 | 1986 | 1982 | 1982 | 1986 | 1986 | 1988 | 1988 | 1984 | 1986 | 1986 | 1988 | 1988 | 1989 | 1988 | 1988 | 1980 |
| Main jet | 122 | 118 | 122 | 118 | 125 | 135 | 135 | 135 | 130 | 125 | 125 | 125 | 135 | 125 | 135 | 135 | 112 |
| Pilot jet | 52 | 52 | 60 | 60 | 50 | 48 | 48 | 48 | 50 | 50 | 50 | 50 | 48 | 48 | 48 | 48 | 50 |
| Starter jet | 75 | 75 | 75 | 75 | 75 | 75 | 75 | 75 | 75 | 75 | 75 | 75 | 75 | 75 | 75 | 75 | 75 |
| Needle (clip) | K 2 (2) | K 2 (2) | K 2 (2) | K 2 (2) | K 23 (3) | K 27 (2) | K 27 (2) | K 27 (2) | K 23 (3) | K 23 (3) | K 23 (3) | K 23 (3) | K 27 (2) | K 27 (3) | K 27 (2) | K 27 (2) | K 27 (2) |
| Atomiser | 260 AB | 260 AB | 260 AB | 260 AB | 264 AB | 261 AB1 | 261 AB1 | 261 AB1 | 264 AB | 264 AB | 264 AB | 262 AB | 261 AB1 | 261 AB1 | 261 AB1 | 261 AB1 | 262 AB1 |
| Slide | 60/3 | 60/3 | 60/3 | 60/3 | 503 | 503 | 503 | 503 | 503 | 503 | 503 | 503 | 503 | 503 | 503 | 503 | 503 |
“–” means: not fitted on this model, or not documented in the source.
Important: figures apply to standard condition
These factory figures apply to standard condition with the original air filter and original exhaust. Any modification (open bellmouths, different exhaust, camshaft …) changes the airflow and calls for a revised setup.
Compiled from several sources – chiefly official Dell'Orto application catalogues and original workshop manuals – and cross-checked against factory tables and community knowledge. Details: Sources & method.
Tuning guide: running lean / running rich
First narrow down the load range in which the problem occurs — then it is clear which part is responsible. The mapping follows Dell'Orto tuning literature and the Moto Guzzi workshop manuals: from idle to roughly 1/4 throttle the pilot jet and mixture screw are in charge, from roughly 1/8 to 3/4 throttle the jet needle (clip position) and atomiser, and from roughly 1/2 throttle to full load the main jet.
| Symptom | Load range | Responsible | Direction |
|---|---|---|---|
| Pale, greyish-white plugs; flat and gutless at the top end; overheating | from ~1/2 to full throttle | main jet | try one size larger |
| Runs better on choke; popping/banging on the overrun | idle to ~1/4 | pilot jet + mixture screw (check for air leaks first) | richer: larger jet or screw further out |
| Hesitation/flat spot when opening the throttle | transition (accelerator pump) | pump jet/pump function, then needle position | richen, check function |
| Surging/leaning out at steady speed and mid throttle | ~1/8 to 3/4 | jet needle (clip) and atomiser | raise the needle one notch (clip lower) = richer |
| Sooty black plugs; burbling running; smell of fuel; high consumption | narrow it down: idle ↔ mid ↔ full | depending on range: pilot jet / needle + atomiser / main jet | leaner: smaller jet or needle lower |
| Gets worse the hotter the engine runs | usually idle/part throttle | overall setup too rich; also check float level | lean it out, check the float height |
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. Your anchor is always the factory value for your model (table above) — on the PHF 30 the documented factory main jets range from 112 to 135. Work from there in single steps in the diagnosed direction.
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.
Matching jet set
A set around the factory value (main jets in steps either side) covers the range you need while dialling in – only a test on the engine shows the final size. Ready-made sets per model are in preparation.
Matching parts for Dellorto PHF 30
Parts that are usually replaced when overhauling this carburettor range.
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 T3 (bored to 995 cc) — PHF 30
Condition/modifications: Open bellmouths with gauze, twin-plug ignition (DMC), hot camshaft
Jetting used: Main jet 120 (on the carburettor seller's recommendation), later 110 tried — pilot jet 65, later 60 (rest of the setup not stated)
Result according to the report: UNRESOLVED EXAMPLE: the engine ran rich on every combination tried (permanently sooted plugs). Community advice: take a lambda reading instead of carrying on guessing. Shows the limits of the spark-plug method on heavily modified engines.
Source: guzzisti.de
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