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[Datsun 1200 encyclopedia]

Mikuni PHH

From Datsun 1200 Club

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Category: Fuel System

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 made the PHH series from around 1970 until 1995. A PHH 50 was also made but are too big for regular A-series engines. Mikuni "Solex" is far more popular than Webers in Japan.

Contents

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

10425.jpgAlbum click to view

Nissan Competition used to sell Mikuni jet parts.

152.jpgAlbum click to view 787.jpgAlbum click to view 377.jpgAlbum click to view 381.jpgAlbum click to view

Mikuni PHH uses the same bolt pattern as Weber DCOE and Dellorto DHLA, so any traditional manifold will work with PHH carburetors.

10430.jpgAlbum click to view 13079.jpgAlbum click to view 13078.jpgAlbum click to view

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.

See main article: Intake Manifold

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.

See main article: Sidedraft Air Filters

7766.jpg 24885.jpg

LHD Fitment

Space for twin sidedrafts on LHD 1200s is limited because the brake master cylinder is on the carburetor side of the engine.

 See main article: LHD Sidedrafts

Heat Shield

Carb heat plate

25550.jpgAlbum click to view

キャブ ヒート プレート

Adjustment

Idle Speed and Mixture Adjustment

  1. Warm engine fully
  2. Adjust curb idle speed to 900 rpm
  3. Slowly turn mixture screw out until the engine speeds up, then keep turning out until engine starts to slow down slightly (overly rich)
  4. Screw in (clockwise) until engine slows down (lean). Turn back out til it runs fastest (Best Lean)
  5. Repeat for second barrel of the carburetor
  6. 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

5212.jpgAlbum click to view 9863.jpgAlbum click to view

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
8988.jpgAlbum click to view

Center Pull

Center Pull - Need the floating lever for the carburetors. In essence, a single throttle lever, with its own balance screw
dcoe_linckage.gif

Center Pull needs only one carb-pull, eliminating the separate throttle adjustments. The center floating linka has its own balance screw
15692.jpgAlbum click to view 15691.jpgAlbum click to view

Single Carb Linkage

For bolt-style manifolds
20641.jpgAlbum click to view

Quadrant

Nissan cable quadrant
11496.jpgAlbum click to view 11497.jpgAlbum click to view 11368.jpgAlbum click to view

Generic cable bracket
11506.jpgAlbum click to view

Throttle Lever

Universal carby throttle lever
556.gifAlbum click to view

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.

DSC06105.jpg

  • Starter: Yellow circles. Connect choke cable to these.
  • Pilot Screws: yellow arrows
  • Idle speed screws: Green arrows


  • Mikuni PHH Carburetor Service Manual

DSC06069.jpg

  • 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

See Mikuni PHH Jetting

Parts

See Mikuni Jets

Parts breakdown diagram
parts_breakdown.jpg parts_list.jpg

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)
outer_venturi.jpg

Nissan Competition

Nissan Competition sold Mikuni kits for Datsuns, including these for A-series engines. From the 1984 Nissan Competition catalog page 40.

th_Competition198440.jpg
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.

mika.jpg mikb.jpg

40mm Mikuni

40MM MIKUNI/SOLEX INDUCTION SYSTEM

23783.jpgAlbum click to view

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

23784.jpgAlbum click to view

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

Competition198462.jpg Competition198463.jpg

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

Excel%20-%20Power%20%20kit%20-%20JDM.jpg

Linkage

Mikuni branded manifolds have a larger diameter linkage shaft.

Tomei manifold?
24885.jpgAlbum click to view

Mikuni options
IMG_0918.jpg

Mikuni center-pull linkage
4g6z2o.jpg

imagehfpn.jpg

Mikuni_Linkage_Small_06.jpg

Generic Twin-Pull
9463.jpgAlbum click to view

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
8988.jpgAlbum click to view

Center Pull

Center Pull - Need the floating lever for the carburetors. In essence, a single throttle lever, with its own balance screw
dcoe_linckage.gif

Center Pull needs only one carb-pull, eliminating the separate throttle adjustments. The center floating linka has its own balance screw
15692.jpgAlbum click to view 15691.jpgAlbum click to view

Single Carb Linkage

For bolt-style manifolds
20641.jpgAlbum click to view

Quadrant

Nissan cable quadrant
11496.jpgAlbum click to view 11497.jpgAlbum click to view 11368.jpgAlbum click to view

Generic cable bracket
11506.jpgAlbum click to view

Throttle Lever

Universal carby throttle lever
556.gifAlbum click to view

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:
Solex_linkage.jpg

16688.jpgAlbum click to view 16537.jpgAlbum click to view

th_DSC_0935_zps9645c43e.jpg th_DSC_0923_zpsb8defff7.jpg 

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