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Mikuni PHH 40 and PHH 44 sidedraft carburetors are a licensed version of the famous Solex sidedraft carburetor. They may be marked Mikuni, Solex or both. They use the same base flange pattern as Weber DCOE and Dellorto DHLA carburetors. Mikuni was the brand Nissan Competition sold for A-series engines. Mikuni "Solex" is far more popular than Webers in Japan.
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Overview
Mikuni bought the SOLEX PHH license in the early 1970s and thoroughly redesigned it since then. The only parts in common between these two carbs are the diaphragm accelerator pump arrangement. The Mikuni now resembles a cross between a Weber DCOE and a Solex. They are the "set and forget" sidedrafts. Mikuni North America is the primary jet supplier. Reference: bimmers.com
Mikuni made the PHH series from around 1970 until 1995. A PHH 50 was also made but are too big for regular A-series engines. Nissan Competition used to sell Mikuni jet parts.
Mikuni PHH uses the same bolt pattern as Weber DCOE and Dellorto DHLA, so any traditional manifold will work with PHH carburetors.
Sizing
As with any carburetor, the single most important specification is the venturi (choke) size -- not the barrell size. So a 40 or 44 is not the question. The question is which choke size should be used.
See main article: Carburetor Sizing
Intake Manifold
Weber DCOE, Dellorto DHLA and Mikuni/Solex PHH use the same manifolds. Single or Twin manifolds are available, for round-port or oval-port A-series engines.
Vacuum Connection
Drill & tap the boss for a tube fitting. Can be used for power brakes, distributor vacuum advance.
Air Filter
Many use simple screens over the carburetor, which keep large objects out of the engine. This (or no screen) provides the fullest "awesome sidedraft sound", but at the expense of increased engine wear.
For filtering, the easiest thing is sock filters, but all sorts of regular and remote filter can be used.
LHD Fitment
Space for twin sidedrafts on LHD 1200s is limited because the brake master cylinder is on the carburetor side of the engine.
Heat Shield
Carb heat plate キャブ ヒート プレート
Adjustment
Idle Speed and Mixture Adjustment
- Warm engine fully
- Adjust curb idle speed to 900 rpm
- Slowly turn mixture screw out until the engine speeds up, then keep turning out until engine starts to slow down slightly (overly rich)
- Screw in (clockwise) until engine slows down (lean). Turn back out til it runs fastest (Best Lean)
- Repeat for second barrel of the carburetor
- If a twin-carb setup, repeat for the second carburetor
To get a 'feel' for this adjustment, turn the screw by half turns clockwise and anticlockwise till you hear the engine speed up and slow down. Then fine turn with 1/4 turns. Do this repeatedly until you are confident of the results.
Linkage
Linkage depends in part on the manifold you use. Does it have bolt-bosses for linkage? Or does it have built-in linkage bar?
Side Pull
Tomei manifold Side Pull. Nismo/Tomei manifold have built-in bar towers and use a large diameter cross bar
Center Pull
Center Pull - Need the floating lever for the carburetors. In essence, a single throttle lever, with its own balance screw
Center Pull needs only one carb-pull, eliminating the separate throttle adjustments. The center floating linka has its own balance screw
Single Carb Linkage
For bolt-style manifolds
Quadrant
Fan lever - Harada Shosho company
Nissan cable quadrant
Generic cable bracket
Throttle Lever
Universal carby throttle lever
Features
- Mikuni recommended fuel pressure is 2.84 - 4.98 psi
- Mikuni calls the idle-mixture screw the "Pilot" screw.
- Carb flange same as DCOE. The air cleaner side bolts are spaced slightly different. Elongating DCOE air cleaner holes lets them fit on the PHH.
- Choke: A most interesting feature of the PHH is that instead of a choke butterfly valve for cold-start enrichment, it using an enriching circuit called a "starter" which rotates to open the starter jet.
- Starter: Yellow circles. Connect choke cable to these.
- Pilot Screws: yellow arrows
- Idle speed screws: Green arrows
- Mikuni PHH Carburetor Service Manual
- Size is stamped on the throttle blade
- 165 = 1.65 inch (40 mm)
Fuel Pump
Mikuni recommended fuel pressure is 2.84 - 4.98 psi. A stock A14 pump should work fine -- they are rated 2.8-3.8 pounds (early A12 fuel pump was lower pressure).
You can easily test the fuel pump with a vacuum/pressure gauge with engine idling. Then remove hose and see how many CCs come out in 60 seconds. A14 pump at 1000rpm should pump minimum of 1.3 liter.
That A14 rating of 1.3/minute is good for 125 HP engine. That's a pretty hot street motor, not many A14s can do that naturally aspirated. For a racing A14 you'll want a higher volume pump.
So test your pump. It may put out 1.5 liter/minute. Then no worries even on a very hot street A14.
Tuning
Parts
See Mikuni Jets
Parts breakdown diagram
1 Screw, Jet Chamber Cover 2 Washer 3 Cover, Jet Chamber 4 Gasket, Jet Chamber Cover 5 Banjo Bolt 6 Washer 7 Filter Assembly 8 Fuel Pipe Assembly - "T" 9 Fuel Pipe Assembly - 90 10 Screw 11 Float Adjusting Screw 12 Nut, Float Adjusting Screw 13 Plate, Float Adjuster 14 Gasket, Float Adjuster 15 Arm Assembly, Float Adjuster 16 Spring, Float Adjuster 17 Float Chamber Cover Assembly 18 Gasket, Float Chamber Cover 19 Washer, Needle Valve 20 Needle Valve Assembly - (1.2, 1.5, 1.8, 2.0, 2.5) 21 Plate 22 Float Assembly 23 Pin, Float 24 Jet, Main Air - 60-300 (increments of 10) 25 Main Bleed Pipe - M, N, P, Q, R. 26 Jet Block Assembly 27 Main Jet - 50-210 (increments of 2.5), 220, 240, 250 28 Pilot Jet - 25-110 (increments of 5) 29 Gasket, Small Venturi 30 Nut 31 Washer 32 Stud Bolt 33 Air Funnel (L=25mm) 35 Venturi, Small 36 Venturi, Large (32mm ID) 37 Screw, Throttle Adjusting 38 Spring 39 Bracket, Throttle Stop 40 Screw 41 Spring, Throttle Return 42 Nut 43 Washer 44 Throttle Lever Assembly 45 Seal 46 Nut 47 Set Screw, Venturi 48 Set Screw, Venturi 49 Screw 50 Screw 51 Pump Cover 52 Pump Diaphragm 53 Pump Spring 54 Gasket, Pump Cover 55 Pump Body Assembly 56 Gasket, Pump Body 57 Split Pin 58 Washer 59 Spring, Pump Rod 60 Pump Rod 61 Connecting Rod 62 Plug Screw 63 Washer 64 Collar 65 Pilot Screw 66 Gasket, Pump Nozzle 67 Pump Nozzle - 30-60 (increments of 5) 60-90 (increments of 10) 68 O-ring 69 Pump Plug 70 Ball 71 Pump Weight 72 O-ring 73 Pump Plug 74 Bracket Assembly 75 Screw 76 Starter Disc 77 Spring, Starter Disc 78 Snap Ring 79 Starter Cover 80 Terminal 81 Bolt 82 Washer 83 Spring, Starter Return 84 Bracket, Starter 85 Cooling Body Assembly 86 Starter Jet (Air Jet) - 60-300 (increments of 10) 87 Spring 88 Damper Spring
Venturis (#36 in diagram)
Nissan Competition
Nissan Competition sold Mikuni kits for Datsuns, including these for A-series engines. From the 1984 Nissan Competition catalog page 40.
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This induction system requires the use of the GX or competition cylinder head. With appropriate jetting and venturi sizing this system can be applied to any modified A-series engine. |
40mm Mikuni
40MM MIKUNI/SOLEX INDUCTION SYSTEM
This induction system requires the use of the GX or competition cylinder head. With appropriate jetting and venturi sizing this system can be applied to any modified A-series engine.
6010-H2310 40MM CARB SET Main jet 120 Air jet 180 Pilot jet 50 Venturi 33mm 99996-H1140 INTAKE MANIFOLD 99996-H1149 STUD & PLUG KIT Required when installing 99996-H1140 99996-H1150 MANIFOLD GASKET 14330-H2310 HEAT SHIELD (2) 16174-H2310 INSULATOR (4) 16174-M0820 INSULATOR (FWD) Inclined 10° (4) 16176-H2310 INSULATOR GASKET (8) $2.70 USD 16360-H2310 LINKAGE ASSY 18200-25720 ACCELERATOR CABLE
44mm Mikuni
44MM MIKUNI/SOLEX INDUCTION SYSTEM
This induction system requires the use of the GX or competition cylinder head. With appropriate jetting and venturi sizing this system can be applied to any modified A-series engine.
16010-M0820 44MM CARB SET Main jet 160 Air jet 180 Pilot jet 55 Venturi 37mm 99996-H1144 INTAKE MANIFOLD 14001-M0820 INTAKE MANIFOLD (FWD) 99996-H1149 STUD & PLUG KIT Required when installing 99996-H1144 99996-H1150 MANIFOLD GASKET 14330-H2310 HEAT SHIELD (2) 16174-20100 INSULATOR (4) 16176-20100 INSULATOR GASKET (8) $2.70 USD 16360-H5720 LINKAGE ASSY 18200-25720 ACCELERATOR CABLE
Accessories
Mikuni PHH|Mikuni/Solex Accessories * Main Jets * Air Jets (Countersunk Type) * Pilot Jets * Outer Venturi (40PHH) * Outer Venturi (44PHH) * Needle Valve ASSY * Velocity Stack * Jet Blocks * Main Bleed Pipe (Emulsion Tube)
1976 Parts
From Datsun Competition Parts manual April 1976 (all parts NLA)
SOLEX MAIN JETS (2 required per carburetor) 16033-25922 110 16033-25923 115 16033-25924 120 16033-25925 125 16033-25926 130 16033-25927 135 16033-25928 140 16034-25522 145 16034-25521 150 16034-25520 155 [150] $8.08 USD 16033-25528 160 16033-25520 180 16033-25521 190 16033-25522 200 16033-25523 210 16033-25524 220 16033-25525 230 16033-25526 240 16033-25527 250
SOLEX AIR JETS (Countersunk Type) 16036-H0222 120 16036-H0223 125 16036-H0224 130 16036-H0225 135 16036-H0226 140 16036-H0227 145 16036-H0228 150 16036-H0229 155 16036-25720 160 16036-25724 165 170 16036-25725 175 16036-25722 180 16036-25726 185 16036-25521 190 16036-25723 200 16036-25722 210 16036-25723 230 16036-25720 250
SOLEX NEEDLE & SEAT ASSEMBLY (NLA) 99996-M1000 Size 2.0 mm
SOLEX CHOKES (all NLA) 16017-A0200 32mm (40mm Carb.) 99996-M1138 38mm (44mm Carb.) 99996-M1140 40mm (44mm Carb.)
36PHH
EXCEL power kit upgrade was offered aftermarket by Kyoritsu Sales.
See Main Article: Kyoritsu
Linkage
Mikuni branded manifolds have a larger diameter linkage shaft.
Tomei manifold?
Mikuni options
Mikuni center-pull linkage
Generic Twin-Pull
Linkage depends in part on the manifold you use. Does it have bolt-bosses for linkage? Or does it have built-in linkage bar?
Side Pull
Tomei manifold Side Pull. Nismo/Tomei manifold have built-in bar towers and use a large diameter cross bar
Center Pull
Center Pull - Need the floating lever for the carburetors. In essence, a single throttle lever, with its own balance screw
Center Pull needs only one carb-pull, eliminating the separate throttle adjustments. The center floating linka has its own balance screw
Single Carb Linkage
For bolt-style manifolds
Quadrant
Fan lever - Harada Shosho company
Nissan cable quadrant
Generic cable bracket
Throttle Lever
Universal carby throttle lever
Adjustment
You need to adjust the 1200 Throttle Cable to take up extra slack in it at idle (otherwise it may not open the carbs all the way at full throttle). For a little play, cut a piece of rubber hose, slit it down the middle and put between the clamp and the cable. If there is a lot of play, you can go to the pedal inside the car and wrap the extra wire around the pedal shaft once.
spacer between cable and bracket:
chris1200t
dual Mikuni-Solex 40mm | custom-made 29mm venturis for 1200cc engine
linkages | A12
A12 bored out 40 thousands inch (+1.0 mm = 1204cc), flat-top pistons, 10.8:1 compression ratio, diamond lapped decked block and shaved head, ported, A15 inlet valves/Mazda 1300 exhaust valves, double valve springs, adjustable timing gear, 34/72 cam, dual 40mm solex's and Hi-Tech extractors
