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

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

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.

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.

Remove Carburetor Per Lab#2 Instructions Use written instructions

Remove Fuel Tank Per Lab#4 Instructions Use written instructions

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

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

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

Remove Valve Cover Use 10 mm Socket Check gasket for damage

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

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

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

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

Measure Valve Clearance Bring piston to just past TDC on compression stroke Exhaust clearance .009-.011 Intake clearance .004-.006 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

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.

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

Piston Movement Pull on recoil rope Observe piston movement in cylinder

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.

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

Install Cylinder Head Use a 10 mm socket Step-Torque sequence 75-150-220 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

Adjust Valve Lash Piston needs to be at ¼" past TDC Install valve caps on valve stems Properly orientate rocker arms Intake valve .004-.006 Exhaust valve .009-.011 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 .004-.006” ii)     Exhaust Valve .009-.011”

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  

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

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

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

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

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

Install Fuel Tank Per Lab#4 Instructions Use written instructions

Install Carburetor Per Lab#2 Instructions Use written instructions

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