Honda 750 4 Cylinder Motorcycle Engine

11202 H o n d a 7 5 0 4 Cylinder Motorcycle Engine

Until 1971, the super-bikes of road racing were usually powered by single-cylinder 500cc high-revving engines that were hand-assembled and bench tested in Europe. Although there were four-cylinder motorcycle engines such as the Henderson or Ariel Square-four, they were not competitive and were regarded suitable for touring bikes rather than racing machines.

At the Daytona races in 1971, a mass-produced four-cylinder 750cc engine made all other motorcycle engines obsolete overnight. The Honda 750 super-bikes swept the race and forever changed the complexion of motorcycle racing all over the world. The basic design of the 750 has been refined, enlarged or reduced in displacement, but the superb design of the Honda 750 lives on today, powering hundreds of thousands of motorcycles in every country.

Designed with a single overhead cam, the four-cylinder Honda produced 67hp at 8,000 rpm, sufficiently powerful to propel the Honda motorcycles to speeds well in excess of 100mph.

Your Minicraft model of the Honda 750 uniquely captures the internal workings of the motor, featuring removeable panels to watch parts in motion revealing the operation of the original. PARTS LAYOUT DIAGRAM

(P arts F4/F5 are not us ed) (P arts I7/I 8 are not us ed)

1 2 3 4 5 6 7 8 9 10 11 12A 12B 2x 8x 8x 8x 4x 4x 2x 2x

14 16 17 (Light Bulbs) 15 Vinyl tube Black wire Red wire BEFORE YOU BEGIN Your MINICRAFT Honda engine model features many functional parts to display the operation of the real engine. It is highly recommended to review the instructions thoroughly before beginning assembly. It is very important to use cement or glue sparingly so as to not interfere with operation. Parts are prepainted or plated, so no additional painting is necessary. Carefully scrape paint or Cement DO NOT Cement Cut or scrape plating from areas of parts that will be glued together. Always test-fit parts before gluing. 1 CRANKSHAFT & CONNECTING RODS 2 PISTONS H27 Place (do not glue) H27 H26 Connecting Rods H26 and Glue piston halves E14 H27 on the round bearing together over rod ends. pins on E14 and E11. E13 B4/9/11/14 Apply glue only to the Apply a small amount of edges of the piston halves, E11 H26 glue to the square shaped not to the pins inside. The E9 pins on E10/13/11 one at a pistons must be free to E10 E16 time and press in position move on the rod ends. as shown.

Make sure parts H27 are up B5/10/12/15 E12 and H26 are in the down E15 position and all move freely around the pins. Using part numbers ASSEMBLY 1 ASSEMBLY 2 shown, make four pistons. (SHOWN COMPLETED) 3 MOTOR AND CRANK ASSEMBLY

Press E31 and E32 on each end of the square drive shaft. Gluing one side at a time, glue E31 into the square hole on E14, and E32 into the square hole on E16. Be sure the crankshaft assemblies are aligned ASSEMBLY 2 as shown.

20 Glue F24 to F21 and press onto the center shaft.

F21

E32 E31

20 E31 NOTE Note part locations F24 Carefully bend four small tabs on Part 20 upward to a 90 degree angle.

ASSEMBLY 1

WIRING REFERENCE DIAGRAM

D C B A D1 C1 B1 A1 We recommend that each time you assemble wires during the

A2 D2 assembly of your kit, you check it against the wiring diagram to make B2 sure you have not made an error. C2 5 Each wire should be cut to the approximate length shown and E6 stripped of plastic for about 1/2" at each end. Twist ends together after F29 stripping. 3X 1" RED D • 14" RED WIRE JUMPER WIRES INSIDE 11" VINYL TUBE 4

E • 14" BLACK WIRE Note only 'E' wire is Black, all TUBE " VINYL 1 2 INSIDE 11 - + others are Red.

MOTOR Metal part numbers are shown circled.

A • 2 3/4"RED WIRE B • 4 3/4"RED WIRE 4 KICK STARTER SWITCH

Apply glue to these edges only F1 Place the ends of wires A and D into the holes on fixed F2 contact 1 and press onto the two small pins on part 2 C1. Glue part E23 on top of the pins. Lightly lubricate F36 part F36.

Place the end of wire C into the slot on F36. Snap part Clip part 2 onto 2 over the wire and around F36 as shown. Carefully part F36 with a apply glue to edges only of parts F1/2 and place in E23 small screwdriver to trap wire end position over part F36. Do not allow glue to touch part F36, as it must be free to rotate. 1 Wire C to Battery Wire A C1 to motor

Wire D to part F29

5 GEAR BOX

Wire A to switch Secure wires A and B to motor terminals as shown. Place the stripped end of the wires in the terminal holes and twist to secure wires. The wires must not touch the metal frame. Use care if soldering connections to not damage the motor from excessive heat. Set the motor assembly over the four holes and secure with screws passed Wire B to battery throught the small tabs on the gear box. Lightly lubricate the ends of the crankshafts and gears.

6 CRANK CASE END COVER

D3 Glue parts together as shown.

D2 7 SPROCKET AND DRIVE SHAFT

LONG SHORT Glue F22 to F23 and press onto metal shaft. Slide on parts F6 and F3 as F3 F38 shown. Press sproket F30 on end Apply Glue to these edges Metal shaft Do not allow glue to touch shaft shown. Loop drive belt 15 onto 16 pulley F22/23. F30 F6 F23 F22 F6 Place assembly on C1 as shown, F3 applying glue to the edges of the 15 mounting panels as shown. Slide pulley so the belt is in line with the G12 drive pulley. Pull belt over pulley after glue is thoroughly dry.

Bring wire D through the corner of C1, and glue part G12 in place.

Wire D C1

8 BATTERY BOX

G4 Insert the two contacts 3 through F27. Attch wires to terminals as shown Wire B G4A (also refer to wiring diagram). Bend Wire C the contacts to hold them in place. Wire E F27 Glue G4A to battery support G4. Route wires as shown and glue remaining parts together as shown. F27

3 9 CRANKCASE

G13 C2 Glue C2 and G13 to C1. Make sure that the pistons and drive belt pass through the holes provided. It is suggested to attach a string to the drive belt in the event it falls inside during assembly.

Make sure belt is on the pulley throughout the final assembly.

Wire E Wire A C1 10 DYNAMO AND TRANSMISSION COVER

Route wires as shown. Slide Vinyl Vinyl tubes tubes over wires. Glue all parts in place Wire E (11" each) as shown.

Wire D

B3 E29

11 DISTRIBUTOR AND CLUTCH COVER

E26 Turn part F36 in direction of arrow as far as it will move and leave in this F28 B8 position.

Glue all other parts in position as shown.

E30

F36

12 OIL PAN

F26 F25 Glue all parts in position as shown.

G28 Fit pins into holes E21 E22

G27

I9 13 KICK STARTER SWITCH

E25 Glue parts B16/17 together ove the pin on part B2. Do (B1) not allow glue to touch pin. Glue E25 to E24 over the E24 shaft of B2. Glue this assembly to the end of the switch shaft (F36) protruding from part B1. Do not allow glue to touch the rotating surface of F36. Allow this assembly to dry thoroughly. B2

B16 B17

14 GEAR SHIFT PEDAL

Glue all parts together as shown and add the finished assembly to the transmission cover (part B7).

(B7)

B6 E19

E20

15 BATTERY COVER

I3 4

Place I3 through hole in B13 and carefully glue I4 to I4 B13 end. Do not allow glue to touch moving part. Secure battery terminal 4 in place with screw as shown. When glue is thoroughly dry, place on engine and turn I4 to lock. 16 VALVE AND HEAD ASSEMBLY

H37/38/39/40 Glue cam followers H37/38/39/40 to valve stems H32/33/41/42. Lightly lubricate each stem, then thread a spring and washer onto each stem. H32/33/41/42 Place one in each head half G17/18/19/20.

Spring Press lightly to compress spring, then glue a valve head H16/17/18/19 Washer 7 G17/18/19/20 to each. Spring must remain compressed until the glue dries.

Make two sets of each assembly. H16/17/18/19

17 SPARKPLUGS

Make four sets of sparkplugs H6 and H7 with bulbs provided, then glue to cylinder heads as H6/H7 shown. Press bulb completely into parts H6/7 Glue on head assembly to each cylinder A1/2/3/4. Note the head assemblies fit to the larger flanged ends of the cylinders.

18 MOUNTING THE CYLINDERS

Align at center Place (do not glue) one cylinder assembly in each hole I2 in part J. Be sure to align each cylinder exactly, payong Plug attention to the position of the sparkplugs. It is recommended to tack each in place with a small amount of glue to allow Plug removal at a later time if the valves need to be realigned. Plug J Place (do not glue) part I2 to check fit and alignment. File or sand any edges on J which Plug make I2 difficult to assemble and remove. This cover enables you to see the working parts of the cylinders. 19 CYLINDER HEAD COVER

F35 Glue plugs F11/12/34/35 into position as F12 shown. Each plug will pass through the F34 locating hole and is to be glued by the small tab on each part. F11

Apply slow-setting glue to the mating edges of part C2 on which part J will attached, then set part J in place with a piston in each clear cylinder. Pull the belt through the slot in part J as shown. Separate plug wires as Wire Wire Wire Wire Wire Wire Wire shown and pass through the holes in D1 as C2 A2 D2 B2 C1 B1 A1 shown. Glue part D1 to J.

Refer to Step 20 for Camshaft assembly instructions. Attach wires to part F29 as shown. Do not glue part in place until camshaft assembly is complete and aligned.

F29 A2 D2

Wire D1 A B B2 C2

3X 1" Red Wire D D Wires to Switch (J)

Pass wires through holes, then press eyelets 6 through to secure.

(C2) 20 CAM SHAFT ASSEMBLY

Place terminal 5 into slots in E6 and bend tabs to secure. Glue E5 to E6. E6 E5 Smooth all edges of cam parts G25/26/29/30 before assembling cam shaft.

Slide all parts shown onto shaft 17 , starting in the middle with assembly 5 E5/6.

Lightly tap cams with a small hammer to hold position.

G30 G25 G26 G29

D C A IMPORTANT NOTE B Each cam (G25/26/29/30) is marked on one side (A/B/C/D). Be sure to assemble Mark 'D' Mark 'C' Mark 'B' Mark 'A' the cams in the positions shown in the diagram at left, with the markings on the side specified.

17 12A 12B 12B 12A

F29 (Shown in position)

Pass cam shaft assembly through drive belt as shown. Trap assembly between end caps E1 and E2. Position drive belt on assembly E5/6. Glue E1 and E2 to cylinder head cover D1.

Align part F29 so eyelet contacts will touch the contact on part E6 and glue in place. E2

Dress rocker arm supports with a file as shown E1 before proceeding with assembly. F29 (Wi res not shown Glue rocker arm supports E3/4/7/8 in place. for clarity) Inspect all wire connections for accuracy and make final connections.

E8 E4

File mating surfaces of rocker arm supports E3/4/7/8 before assembly to assist proper alignment. 21 CAM SHAFT AND ROCKER ARMS NOTE - Parts are shown in place. Refer to prior instruction step.

Be sure all edges are smooth IMPORTANT NOTE 8 Adjust position of cams on shaft by pushing them on shaft so they align with rocker arms H1/2/3/4.

8 H1/2

(Wire E)

(Wire D)

E7/8 8 J

8 H3/4

Be sure glue on parts E3/4/7/8 is thoroughly dry. Carefully assemble rocker arms (parts H1/2/3/4) using rivets 8 as shown.

Support parts E3/4/7/8 as shown when pressing rivets into place.

Make sure all assemblies are free to rotate.

22 STAY PLATE 23 CARBURETORS

Glue G1 to G3 and F7/8/9/10 Using the parts shown, G2 to G10. Glue assemble four sets of two parts H5 to G8 carburetors. as shown. G2 H13/14 G1 G3 G10 NOTE - Glue parts H9/H36 Place all parts on H33/34 inside as shown first, before Fits under tab G8 and slide two continuing assembly. H8 pins H8 through to retain. Do not H32/35 H5 glue.

H8 Carefully apply small amount of glue to hole in G5 and push ends of I 10/11/12/13 H9/36 pins H8 to retain. G8

H5 H28/29 24 CARBURETOR MOUNTING (PART 1)

G14 Glue parts F32 and H10 between two G9 carburtors, and parts F33 and H10 between the others. Carefully glue carburetors #1 and #2 to part G8.

Glue one side of G11 to installed carburetor #2. Glue carburetors #3 and #4 to part G8, and glue other side of G11 to carburetor #3. #1 #2 G8 Glue part G9 to part G14, then glue this H15 assembly to the carburetors as shown by F32 dotted lines. H10 G11 #3 H15* #4 Carburetors #1 and #2 F33* H10* are shown in place.

*Parts shown in place

25 INLET PIPES 26 CARBURETOR MOUNTING (PART 2)

Glue inlet halves together as shown, using parts as Glue inlet pipes to part listed. J and carburetor assembly from step 24. Glue rings H11/12/20/21 to the ends of inlets. It is recommended to use a slower-setting H11/12 H20/21 glue to allow the inlet pipes to be adjusted to INLET A F13/16 fit. INLET B F14/15 INLET C F17/19 INLET D F18/20

Finished assembly

27 EXHAUST FLANGES 28 VALVE COVER H23

H23 H30

I2 H22 H24 H30 H22 Glue parts in H24 Glue parts in H31 place as place as shown. shown. H31 G23 D4 H25* *Parts shown in place 29 FINAL TEST AND ASSEMBLY Place two AA batteries into the battery box. Be sure they (D4) have the correct orientation and touch all contacts. (B13) Place battery cover B13 in place and turn lock to retain.

Turn the kickstart handle counterclockwise to start, with covers D4/5/12 removed.

• UNDER D4 VALVE COVER Cams will move the rocker arms, which push the inlet and exhaust valves open and closed. On the real engine, these (D2/3) allow gas and air to enter, and burnt exhaust gas to escape.

• WITH I2 REMOVED You will see the valves open and close, and the plugs will flash every four strokes of each piston. The pistons will be pushed up and down with the connecting rods. In the real engine, the combustion in the cylinder creates the power to force the pistons up and down, causing the crankshaft to ON turn and drive the machine. (B2) REMOVAL OF D5 This will expose the crankshaft and the movement of the connecting rods.

The covers are designed to be removed and replaced for (B1) shelf display. Do not glue these parts in position. (D5) (I2) (B3)

30 DISPLAY STAND

Snap to D2/3 (do not glue)

E27 E28 E17

I5 E18 (shown in place) I1

Snap to C1 (do not glue) TROUBLESHOOTING TIPS 1 • MOTOR WILL NOT START Remove battery cover and touch the top of both batteries with a metal object. If the motor starts with the switch on, the problem is the battery contact 4. Check terminal 4, and bend the ends upwards so they have spring action. Bend

If this does not solve the problem, check the position of the + - batteries. The center of the batteries should be approximately 1/2" from the outside of the case as shown. If this is the problem, cut a strip of waste plastic and glue it to battery support G4 and part F27. If this doesn't solve the problem, 1/2" check all external wiring. If no fault can be found, the kit will have to be taken apart and checked for improper internal wiring.

2 • MOTOR ROTATES IN WRONG DIRECTION This can only be caused by an error in the internal wiring. To correct, reverse the position of the batteries, positive ends exchanged with negative. Starting the motor in the wrong direction may damage contact 5. To fix this, very carefully slide pulley E6 away from switch plate F29. Reshape contact 5 with tweezers and reposition the pulley so that contact 5 is almost flat against part F29. 5

3 • PLUGS DO NOT FLASH Check all external wiring against wiring diagram. If no problem can be found, examine contact 5 to make sure it touches all the eyelets on F29 as it rotates. Push pulley E6 closer to F29. If this doesn't work, slide the pulley back as described in tip 2 and reform contact 5.

4 • MOTOR WILL NOT TURN CAM SHAFT Check all valve stems to make sure they move up and down freely. If they are tight because of glue, push and pull on them until they are free. Then lightly lubricate them with oil.

Check all cams to see that the tops are smooth. File off any rough spots. Check the ends of the rocker arms and carefully trim any ends that get trapped with a sharp knife.

Also check to make sure the rocker arms are not too tight. If so, push pins out to free up.

Check to see if contact 5 is damaged or deformed. If so, check tip 2.

5 • VALVES DO NOT OPERATE Check to see that supports E3/4/7/8 are glued in the correct position (see Step 20). If incorrect, break loose, remove excess glue and reposition.

Push the cams into correct location under rocker arms. If this is difficult, remove the end bearings and file part 12A so it allows more movement of the cams. This has been made to the exact length for proper assembly, but if any parts are not glued in the correct position, it will restrict the movement of the cams. The engine will still work if 12A is cut very short, but it will not look exactly correct.

Rotating the valve stems may also help in correcting valve opening problems.

6 • BELT COMES OFF DURING ASSEMBLY Start motor and place the belt on the pulley. It should locate itself.

With care, most assembled kits can be taken apart to correct errors. Use a thin sharp object or knife; wedge between the glued parts and gently pry apart. Be sure to remove excess cement or glue from mating surfaces before replacing.