1. Model 12 Intek Horizontal OHV
Head Removal and Replacement
Lab #5

2. Required Tools 7, 8, 10 mm socket 5/8” sparkplug socket Ratchet wrench
Extension
Inch pound torque wrench
5/8” box wrench
1/8” Allen wrench
Feeler gauge set
Standard screwdriver
Pliers
Optional T-30 Torx bit
Required Tools

3. Systematic Approach
Technicians need to take their time when disassembling an engine. This is not a race!
Listen for instruction when to remove the next piece. Do not work ahead!
Lay assemblies in order as they were removed.
Put fasteners with removed assemblies, or loosely back in bolt holes.

4. Let’s Begin Close fuel shut-off valve
Disconnect spark plug ignition lead from spark plug
Move throttle to stop position
Safety Issues.
Prevent accidental starting of engine.

5. Remove Carburetor Per Lab#2 Instructions
Use written instructions

6. Remove Fuel Tank Per Lab#4 Instructions
Use written instructions

7. Remove Muffler Heat Shield
Use 7 & 10 mm sockets
Use caution! Sheet metal edges can be sharp!
1)     Remove Muffler Heat Shield
Guard To Prevent Touching Hot Muffler. Note: Shield Still Gets Hot

8. Remove Muffler Use 10 mm socket or T-30 Torx bit
Exhaust gasket will probably be damaged during removal
Remove sparkplug using sparkplug socket
1)     Remove Muffler
a)     Reduces Engine Noise
b) Used To Direct Out Going Hot Gases

9. Valve Cover Bolts Make drawing of bolt locations
Indicate size and color of bolt

10. Remove Valve Cover
Use 10 mm Socket
Check gasket for damage

11. Governor Control Panel
Use 10 mm socket
Loosen the 4 black bolts.
Turn the bolts about ¾ of the way out, but do not remove

12. Remove Cylinder Heat Shield
Use 7 mm socket
While lifting up on governor control bracket, work shield out from engine
1)     Remove Cylinder Heat Shield
a)     Shield Directs Air From Blower Housing Across Cylinder Cooling Fins.
b)     Has provision for high tension lead

13. Remove Spark Plug Move throttle control to the stop position
Use 5/8" spark plug socket
1)     Remove Spark Plug
Spark Plug Produces A Spark Just Before The Piston Reaches Top Dead Center On The Compression Stroke. Spark Ignites Fuel Air Mixture, Which Starts A Burn Causing The Piston To Move Down The Cylinder Bore

14. Observe Valve Movement
Pull on starter rope through all 4 strokes
Observe movement of both valves
1)     Remove Cylinder Head
a)     Head Contains Intake Valve.
i)      Acts As A Doorway To Allow Fresh Air-Fuel Mixture Into Cylinder.
ii)     Intake Valve Is Sized Larger Than Exhaust Valve To Maximize Amount Of Intake
b)     Head Contains Exhaust Valve
i)       Acts As A Doorway To Allow Burnt Air-Fuel Mix Out Of Cylinder.
ii)      Must Be Able To Withstand High Temperatures
c)      Valve Guides
i)       Small Tubes Used To Support Valve Stems
ii)      Provide Lubrication For Valve Stems
d)     Valve Seats
i)     Provides A Sealing Surface For The Valves
(1)  Exhaust Seat Must Be Able To Withstand High Temperatures.
(2)  Exhaust Seat Functions To Transfer Heat From Valve To Engine Block.
e)     Rocker Arm Mechanism
i)      Transfers Movement From Push Rods To Valves.
f)      Incorporates Cooling Fins
i)      Used To Dissipate Heat

15. Measure Valve Clearance
Bring piston to just past TDC on compression stroke
Exhaust clearance
Intake clearance
Measure between rocker arm and valve stem cap
1)     Remove Cylinder Head
a)     Head Contains Intake Valve.
i)      Acts As A Doorway To Allow Fresh Air-Fuel Mixture Into Cylinder.
ii)     Intake Valve Is Sized Larger Than Exhaust Valve To Maximize Amount Of Intake
b)     Head Contains Exhaust Valve
i)       Acts As A Doorway To Allow Burnt Air-Fuel Mix Out Of Cylinder.
ii)      Must Be Able To Withstand High Temperatures
c)      Valve Guides
i)       Small Tubes Used To Support Valve Stems
ii)      Provide Lubrication For Valve Stems
d)     Valve Seats
i)     Provides A Sealing Surface For The Valves
(1)  Exhaust Seat Must Be Able To Withstand High Temperatures.
(2)  Exhaust Seat Functions To Transfer Heat From Valve To Engine Block.
e)     Rocker Arm Mechanism
i)      Transfers Movement From Push Rods To Valves.
f)      Incorporates Cooling Fins
i)      Used To Dissipate Heat

16. Loosen Rocker Arm and Jam Screw
Use 5/8" wrench and 1/8" Allen wrench
Only need to loosen both pieces about ¼ turn
Turn both rocker arms to the side and remove push rods
1)     Loosen Rocker Arm And Jam Screw
a)     Used To Adjust Clearance Between Rocker Arm And Valve
b)     Remove push rods
i)      Push Rods Are Same Length And Same Material. Some Engines Use Different Materials For Intake Verses Exhaust Push Rods.

17. Remove Cylinder Head Use 10 mm socket
Cylinder head gasket will probably be damaged during removal
Valve assemblies can be removed from head
1)     Remove Cylinder Head
a)     Head Contains Intake Valve.
i)      Acts As A Doorway To Allow Fresh Air-Fuel Mixture Into Cylinder.
ii)     Intake Valve Is Sized Larger Than Exhaust Valve To Maximize Amount Of Intake
b)     Head Contains Exhaust Valve
i)       Acts As A Doorway To Allow Burnt Air-Fuel Mix Out Of Cylinder.
ii)      Must Be Able To Withstand High Temperatures
c)      Valve Guides
i)       Small Tubes Used To Support Valve Stems
ii)      Provide Lubrication For Valve Stems
d)     Valve Seats
i)     Provides A Sealing Surface For The Valves
(1)  Exhaust Seat Must Be Able To Withstand High Temperatures.
(2)  Exhaust Seat Functions To Transfer Heat From Valve To Engine Block.
e)     Rocker Arm Mechanism
i)      Transfers Movement From Push Rods To Valves.
f)      Incorporates Cooling Fins
i)      Used To Dissipate Heat

18. Piston Movement Pull on recoil rope
Observe piston movement in cylinder

19. Reassembly
Technicians need to take their time when reassembling an engine. This is not a race!
Listen for instruction when to add the next piece. Do not work ahead!
Fasteners will need the proper torque values.
Special procedures will be explained.

20. Install Head Gasket
4 holes on head gasket need to be on intake side.

21. Install Cylinder Head Use a 10 mm socket
Step-Torque sequence in. lbs
Install push rods in slots
Insure that tips rest in recess of tappets
1)     Install Cylinder Head
Must Use A Step-Torque Sequence

22. Adjust Valve Lash Piston needs to be at ¼" past TDC
Install valve caps on valve stems
Properly orientate rocker arms
Intake valve
Exhaust valve
1)     Adjust Valve Lash
a)     Instruct How To Find Top Dead Center
i)      Move Piston To ¼” Past TDC
ii)  Insures that compression release will not effect clearance
b)     Adjust Valve Clearance
i)      Intake Valve ”
ii)     Exhaust Valve ”

23. Install Valve Cover Check gasket
Short screw on top, gold screw on bottom, silver screws on sides
Use 10 mm socket
Torque to 45 in. lbs
1)     Install Valve Cover
a)     Short Screw On Top
b)     Gold Screw On Bottom
c)      Other Screws On Side Holes

24. Install Cylinder Heat Shield
Use 7 mm socket
While lifting up on governor control bracket, work shield back into place
Torque to 30 in. lbs
DO NOT OVER TORQUE! Will strip hole, causing replacement of cylinder
1)     Remove Cylinder Heat Shield
a)     Shield Directs Air From Blower Housing Across Cylinder Cooling Fins.
b)     Has provision for high tension lead

25. Governor Control Panel
Use 10 mm socket
Tighten to 60 in. lbs

26. Install Muffler Replace gasket? Use 10 mm socket or T-30 Torx bit
Torque to 100 in. lbs
1)     Install Muffler

27. Install Muffler Heat Shield
Use 7 and 10 mm socket
Torque 7 mm to 30 in. lbs – Tighten these screws first
Torque 10 mm to 60 in. lbs
1)     Install Muffler Heat Shield
a)     Use Caution With Sheet Metal For Sharp Edges

28. Install Spark Plug Use 5/8" spark plug socket Torque to 180 in. lbs
Attach ignition lead
1)     Install Spark Plug
Be Sure Ignition Coil Lead Fits Thru Slot In Heat Shield

29. Install Fuel Tank Per Lab#4 Instructions
Use written instructions

30. Install Carburetor Per Lab#2 Instructions
Use written instructions

31. Success!
Do you have any extra parts?
Do you have any questions?