Dell'Orto PHF 36 – jetting & tuning
Dell'Orto range with accelerator pump; jet needles of the K series. Fitted from the factory to 12 documented models from Ducati, Harley-Davidson, Hesketh, KTM, Moto Guzzi; with accelerator pump (pump jet).
| Make | Model | Year | Version | Designation | Reg. no. | Details |
|---|---|---|---|---|---|---|
| Ducati | 400 F3 Racing (Japan) | 1987 | Japan · left carburettor (MS) | PHF 36 MS | 4670 | view jetting |
| Ducati | 400 F3 Racing (Japan) | 1987 | Japan · right carburettor (MD) | PHF 36 MD | 4671 | view jetting |
| Ducati | 500 L Pantah | 1979 | left carburettor (MS) | PHF 36 MS | 4558 | view jetting |
| Ducati | 500 L Pantah | 1979 | right carburettor (MD) | PHF 36 MD | 4559 | view jetting |
| Ducati | 600 Pantah | 1979 | left carburettor (MS) | PHF 36 MS | 4558 | view jetting |
| Ducati | 600 Pantah | 1979 | right carburettor (MD) | PHF 36 MD | 4559 | view jetting |
| Harley-Davidson | Custom 1000 | 1982 | Standard | PHF 36 HD | 4606 | view jetting |
| Hesketh | V1000 | 1981 | left carburettor (AS) | PHF 36 AS | 4588 | view jetting |
| Hesketh | V1000 | 1981 | right carburettor (AD) | PHF 36 AD | 4589 | view jetting |
| Hesketh | V1000 | 1982 | left carburettor (ES) | PHF 36 ES | 4599 | view jetting |
| Hesketh | V1000 | 1982 | right carburettor (ED) | PHF 36 ED | 4600 | view jetting |
| KTM | Enduro | 1983 | Standard | PHF 36 AS | 4613 | view jetting |
| Moto Guzzi | 1000 SP III | 1988 | Standard | PHF 36 DS/DD | 4676/77 | view jetting |
| Moto Guzzi | 1000 SP III | 1992 | Standard | PHF 36 DS1 | 4691/92 | view jetting |
| Moto Guzzi | California 1100 | 1993 | Standard | PHF 36 DS1 | 4697/98 | view jetting |
| Moto Guzzi | California 1100 | 1994 | Standard | PHF 36 DS1 | 4699/4700 | view jetting |
| Moto Guzzi | California 1100 | 1994 | Standard | PHF 36 DS1 | 4701/02 | view jetting |
| Moto Guzzi | California 3 | 1989 | Switzerland | PHF 36 DS | 4687/88 | view jetting |
| Moto Guzzi | Le Mans 1 | 1975 | Standard | PHF36BS/BD | 4522/23 | view jetting |
| Moto Guzzi | Le Mans 2 | 1975 | Standard | PHF36BS/BD | 4522/23 | view jetting |
| Moto Guzzi | Le Mans 3 | 1981 | no dot on the carburettor | PHF 36 BS/BD | 4585/86 | view jetting |
| Moto Guzzi | Le Mans 3 | 1981 | red dot on the carburettor | PHF 36 BS/BD | – | view jetting |
| Moto Guzzi | Le Mans 3 | 1981 | green dot on the carburettor | PHF 36 BS/BD | – | view jetting |
| Moto Guzzi | Le Mans 3 | 1981 | USA | PHF 36 DS/DD | 4590/91 | view jetting |
| Make | Ducati | Ducati | Ducati | Ducati | Ducati | Ducati | Harley-Davidson | Hesketh | Hesketh | Hesketh | Hesketh | KTM | 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 | 400 F3 Racing (Japan) | 400 F3 Racing (Japan) | 500 L Pantah | 500 L Pantah | 600 Pantah | 600 Pantah | Custom 1000 | V1000 | V1000 | V1000 | V1000 | Enduro | 1000 SP III | 1000 SP III | California 1100 | California 1100 | California 1100 | California 3 | Le Mans 1 | Le Mans 2 | Le Mans 3 | Le Mans 3 | Le Mans 3 | Le Mans 3 |
| Year | 1987 | 1987 | 1979 | 1979 | 1979 | 1979 | 1982 | 1981 | 1981 | 1982 | 1982 | 1983 | 1988 | 1992 | 1993 | 1994 | 1994 | 1989 | 1975 | 1975 | 1981 | 1981 | 1981 | 1981 |
| Version | Japan · left carburettor (MS) | Japan · right carburettor (MD) | left carburettor (MS) | right carburettor (MD) | left carburettor (MS) | right carburettor (MD) | Standard | left carburettor (AS) | right carburettor (AD) | left carburettor (ES) | right carburettor (ED) | Standard | Standard | Standard | Standard | Standard | Standard | Switzerland | Standard | Standard | no dot on the carburettor | red dot on the carburettor | green dot on the carburettor | USA |
| Designation | PHF 36 MS | PHF 36 MD | PHF 36 MS | PHF 36 MD | PHF 36 MS | PHF 36 MD | PHF 36 HD | PHF 36 AS | PHF 36 AD | PHF 36 ES | PHF 36 ED | PHF 36 AS | PHF 36 DS/DD | PHF 36 DS1 | PHF 36 DS1 | PHF 36 DS1 | PHF 36 DS1 | PHF 36 DS | PHF36BS/BD | PHF36BS/BD | PHF 36 BS/BD | PHF 36 BS/BD | PHF 36 BS/BD | PHF 36 DS/DD |
| Reg. no. | 4670 | 4671 | 4558 | 4559 | 4558 | 4559 | 4606 | 4588 | 4589 | 4599 | 4600 | 4613 | 4676/77 | 4691/92 | 4697/98 | 4699/4700 | 4701/02 | 4687/88 | 4522/23 | 4522/23 | 4585/86 | – | – | 4590/91 |
| 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 | view jetting | view jetting | view jetting | view jetting | view jetting | view jetting | view jetting |
“–” 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 36 the documented factory main jets range from 115 to 155. 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 36
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 Le Mans III (850) — PHF 36
Condition/modifications: Open bellmouths with gauze, otherwise largely standard
Jetting used: Main jet 135–140 (depending on the gauze), pilot jet 65, needle K18 in the 3rd notch from the top, throttle slide 60/3, starter jet 70, mixture screws 1.75 turns
Result according to the report: Described by the user as a working setup with open bellmouths. No problems reported.
Source: groups.google.com
User report, no warranty — not a factory figure
Moto Guzzi Le Mans III (850) — PHF 36
Condition/modifications: Converted from airbox to open bellmouths
Jetting used: Main jet 140, pilot jet 60 (rest of the setup not stated)
Result according to the report: NEGATIVE EXAMPLE: the engine got far too hot (around 110 °C after 20 km) with heavy ticking from the heat — the setup after fitting bellmouths was evidently too lean. Shows that switching to bellmouths without consistent richening is risky.
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