EH12, EH17, EH25 - Small Engine Discount
EH12, EH17, EH25 - Small Engine Discount EH12, EH17, EH25 - Small Engine Discount
8. CARBURETOR 8-1 OPERATION AND CONSTRUCTION 8-1 -1 FLOAT SYSTEM The float chamber is located below the carburetor body and, with a float and a needle valve, maintains a constant fuel level during the engine operation. (See Fig. 8-1.) The fuel flows from the fuel tank into the float chamber through the needle valve. When the fuel rises to a specific level, the float rises, and when its buoyancy and fuel pressure are balanced, the needle valve shuts off the fuel, thereby keeping the fuel at the predetermined level. /" PILOT OUTLET \ BY- PASS,, ---- I -a=- -- I AIR INTAKE ! MAIN AIR JET - 46 -
8-1 -2 PILOT SYSTEM The pilot system feeds the fuel to the engine during idling and low-speed operation. The fuel is fed through the main jet to the pilot jet, where it is metered, and mixed with the air metered by the pilot air jet. 0 The fuel-air mixture is fed to the engine through the pilot outlet and the by-pass. At the idling speed, the fuel is mainly fed from the pilot outlet. 8-1-3 MAIN SYSTEM The main system feeds the fuel to the engine at medium-and high-speed operation. The fuel is metered by the main jet and fed to the main nozzle. The air metered by the main air jet is mixed with the fuel through the bleed holes in the main nozzle, and the mixture is atomized out of the main bore, It is mixed again with the air taken through the air cleaner into an optimum fuel-air mixture, which is supplied to the engine. 8-1-4 CHOKE The choke may be used for easy start when engine is cold. When the engine is cranked with a closed choke, the negative pressure applied to the main nozzle increases and draws more fuel accordingly this starting up the engine more easily. 8-2 DISASSEMBLY AND REASSEMBLY Apart from mechanical failures, most of carburetor troubles are caused by an incorrect mixing ratio, which may arise mainly due to a clogged up air or fuel passage in jets, or fuel level variations. In order to assure proper flow of air and fuel, the carburetor must be kept clean at all times. The carburetor disassembly and reassembly procedures are as follows : (See Fig. 8-3.) 8-2-1 THROTTLE SYSTEM (1) Remove the philips screw (1) and throttle valve (2), and pull out the throttle shaft (3). (2) The spring (4) can be taken out by removing the throttle stop screw (5). * Be careful not to damage the throttle valve rim. 8-2-2 CHOKE SYSTEM (1) Remove the philips screw (6) and choke valve (7), and pull out the choke shaft (8). (2) When reassembling the choke shaft, make sure that the cutout in the choke valve faces the main air jet. Meanwhile, when reassembling set the rings (9) and (10) at the right position. 8-2-3 PILOT SYSTEM (1) Remove the pilot jet (ll), using proper tools to avoid damage to it. (2) Reassembly Tighten the pilot jet securely. Otherwise, the fuel may leak, causing engine malfunction. 14 16 15 17 19 A 21 --@ 13 .-e 18 12 Fig. 8-3 - 47 -
- Page 2 and 3: ROBIN ROBIN AMERICA, INC. ROBIN TO
- Page 4 and 5: " . 13-1 13-2 13-3 13-4 13-5 13-6 1
- Page 6 and 7: ~~~~ ~~ Model TY Pe Bore X Stroke P
- Page 8 and 9: 2. PERFORMANCE 2-1 MAXIMUM OUTPUT A
- Page 10 and 11: n 0 EHf7D, B (. ). for B type " kg-
- Page 12 and 13: 3. FEATURES 1. The overhead valve d
- Page 14 and 15: 4-6 CAMSHAFT ‘I’he camshaft for
- Page 16 and 17: 4-12 IGNITION SYSTEM The ignition s
- Page 18 and 19: ROCKER ARM I L - 14 -
- Page 20 and 21: 5-3 DISASSEMBLY PROCEDURES Step Par
- Page 22 and 23: ~~ I Step I Part to remove 1 Proced
- Page 24 and 25: Step Part to remove Procedures Rema
- Page 26 and 27: ~ ~~ ~ ~~ ~~~ ~ I Step Part to remo
- Page 28 and 29: ~~ ~ ~~ Step 18 Part to remove 1 Pr
- Page 30 and 31: Step Part to remove 1 Procedures Re
- Page 32 and 33: Step 26 Part to remove Connecting r
- Page 34 and 35: ~~~~ Step Part to remove Procedures
- Page 36 and 37: TOP RING “N” MARK SECOND RlNC O
- Page 38 and 39: 54-5 BALANCER SHAFT (EH25 type only
- Page 40 and 41: Fig. 5-36 (2) Lubricate the oil sea
- Page 42 and 43: (2) Loosen the lock nut on the rock
- Page 44 and 45: (3) Connect the speed control lever
- Page 46 and 47: 5-5 BREAK-IN OPERATION An engine th
- Page 48 and 49: 6-3 WIRING DIAGRAM STANDARD - Ignit
- Page 52 and 53: 8-2-4 MAIN SYSTEM (1) Remove the bo
- Page 54 and 55: (4) Remove the reel from the starte
- Page 56 and 57: (6) Test the operation of the recoi
- Page 58 and 59: 10-1-3 IGNlTfON SYSTEM Check the fo
- Page 60 and 61: 11. INSTALLATION Engine life, ease
- Page 62 and 63: ITEM T EH12 T EH17 Unit: mrn (in) S
- Page 64 and 65: ~~ ~~~ ~ Ring groove ITEM side clea
- Page 66 and 67: ITEM T STD EH12 Limit Unit: mrn (in
- Page 68 and 69: ~ CONNECTING ROD ITEM T STD EH25 Li
- Page 70 and 71: Unit : mm (in) CAMSHAFT ITEM STD EH
- Page 72 and 73: ITEM T STD EH25 Limit Unit: mm (in)
- Page 74 and 75: 12-3 OIL GRADE CHART I 5w I Compari
- Page 76: ~ ~ ~~~~ ~ ~ 13-4 EVERY 100-200 HRS
8. CARBURETOR<br />
8-1 OPERATION AND CONSTRUCTION<br />
8-1 -1 FLOAT SYSTEM<br />
The float chamber is located below the carburetor<br />
body and, with a float and a needle valve, maintains<br />
a constant fuel level during the engine operation.<br />
(See Fig. 8-1.)<br />
The fuel flows from the fuel tank into the float<br />
chamber through the needle valve. When the fuel<br />
rises to a specific level, the float rises, and when its<br />
buoyancy and fuel pressure are balanced, the needle<br />
valve shuts off the fuel, thereby keeping the fuel at<br />
the predetermined level.<br />
/"<br />
PILOT OUTLET<br />
\ BY- PASS,, ---- I<br />
-a=- --<br />
I<br />
AIR<br />
INTAKE<br />
! MAIN AIR JET<br />
- 46 -
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