Tools & supplies
- Feeler gauge set (metric and imperial)
- Open/box wrenches and sockets (common sizes 7/16–1/2 in; metric 10–13 mm)
- Screwdrivers (flat & Phillips)
- 2 wrenches for two‑nut adjusters or small spanner & screwdriver (depending on adjuster type)
- Socket and breaker bar (to turn crank) or long ratchet for flywheel/crank pulley bolt
- Torque wrench (for valve cover nuts)
- Spark plug socket & ratchet
- Small wire brush, rags, degreaser
- Replacement valve cover gasket
- Light oil (engine oil) and penetrating oil
- Flashlight or inspection mirror
- Gloves, safety glasses

Possible replacement parts (inspect and carry if needed)
- Valve cover gasket (always replace)
- Rocker arm bushings or studs (if worn)
- Pushrods (if bent or scored)
- Tappets/lifters (if worn)
- Valve stem seals, valve springs, valves (if leaking or damaged)
- Locknuts/adjusting screws if rounded or damaged

Safety precautions
- Work on a cold engine unless manual specifies “hot” lash setting. Cold reduces risk of burning and prevents wrong clearance due to thermal expansion.
- Park on level ground, engine off, key removed, parking brake on, wheels chocked.
- Disconnect battery (recommended) to avoid accidental starting.
- Remove spark plugs before rotating engine to make cranking easier and avoid accidental ignition.
- Keep hands, tools, and rags away from moving parts when cranking.
- Use eye protection and gloves.

Overview (what you’re doing)
- You are setting valve lash (clearance) so valves fully close and open correctly. Most TE‑20 engines use rocker arms with adjustable screws and locknuts over pushrods/tappets. Procedure: identify each cylinder’s compression stroke (both valves closed), set clearances with a feeler gauge for intake and exhaust, tighten locknuts, recheck.

Typical clearances (use these only if you don’t have the factory manual; verify if possible)
- Common ranges used on older MF 4‑cyl tractors: intake ≈ 0.20–0.25 mm (0.008–0.010 in); exhaust ≈ 0.30–0.35 mm (0.012–0.014 in). Confirm exact spec in your TE‑20 workshop manual and set cold unless manual calls for hot adjustment.

Step‑by‑step procedure
1. Preparation
- Park, chock wheels, set parking brake. Remove battery negative terminal (recommended).
- Remove hood/air cleaner if needed for access.
- Remove valve cover bolts and lift off valve cover. Clean mating surfaces; remove old gasket.
- Remove spark plugs and keep them safe.
- Clean any dirt around the rocker area so contaminants don’t fall into the engine.

2. Identify cylinder numbering and firing order
- Confirm TE‑20 cylinder numbering and firing order from manual (typical 4‑cylinder firing order 1‑3‑4‑2 but confirm). Knowing cylinder order is essential if you choose to follow the firing sequence method.

3. Turn engine to TDC on compression stroke for cylinder #1
- Use a socket on the crankshaft pulley/flywheel and slowly rotate engine in normal running direction.
- You want TDC (top dead center) on the compression stroke where both valves are closed and there is pressure on the tappet pushrods but rockers are at a neutral/closed position.
- How to confirm compression stroke:
- Look at the rocker arms: both intake and exhaust rockers for the cylinder should be loose (no lift) as you approach TDC; before TDC the intake may open then close; at TDC both valves are closed.
- Another method: feel for compression at spark plug hole (finger over plug or use a compression tester) or mark flywheel and count rotations from known position.
- If unsure, rotate one full turn (360°) from TDC and check again.

4. Set clearances on that cylinder
- With both valves closed at TDC compression, slide the correct thickness feeler gauge between the valve stem tip (or rocker contact) and the rocker adjusting screw/valve head area depending on the design.
- For rocker‑screw + locknut style:
- Loosen the locknut a turn.
- Hold the adjuster screw so it doesn’t turn, or hold screw with a screwdriver/Allen as appropriate.
- Turn the screw until you feel a slight drag on the feeler gauge when sliding it back and forth.
- While holding the screw in position, tighten the locknut to spec (or firmly but avoid overtightening). Recheck clearance after tightening (some locknuts can move the screw).
- For shims or bucket‑type lifters (less likely on TE‑20): follow manual procedure (usually requires removing rocker assembly and measuring shim thickness), don’t guess.

5. Repeat for intake and exhaust on that cylinder
- Intake and exhaust have different target clearances—set both.

6. Move to next cylinder using correct sequence
- Rotate crank 180° (or to next TDC on compression stroke for the next cylinder in firing order) and repeat the process.
- Continue until all cylinders are done.

7. Recheck all clearances
- After torquing all locknuts, go back and recheck each clearance. Tightening adjacent nuts can slightly alter settings.

8. Final assembly
- Clean valve cover mating surface. Install new gasket and valve cover. Torque cover bolts evenly to specified torque (or snug them evenly).
- Reinstall spark plugs, reconnect battery, reinstall air cleaner/hood.
- Start engine and run briefly, listen for excessive valve clatter (too loose) or snapping (too tight). Recheck and adjust if necessary.

How to use the feeler gauge properly
- Insert the blade between the rocker and valve stem (or specified contact points).
- Your feeler should slide with a slight resistance (“light drag”). If it slides too loosely the gap is too big; if it snags and you can’t slide it with slight pressure the gap is too small.
- Use the correct blade thickness for each valve (intake vs exhaust). Keep the gauge straight; don’t angle the blade.

Common pitfalls & how to avoid them
- Setting on the wrong stroke (exhaust stroke or overlap): always ensure TDC on compression stroke (both valves closed).
- Using wrong clearance spec: always confirm with factory manual. Wrong clearances cause noise, poor performance, or valve damage.
- Not rechecking after tightening locknuts: tightening can change the setting — always recheck.
- Over‑tightening locknuts/adjusters: risks stripping threads or bending adjuster. Tighten snugly, don’t crush threads.
- Bending pushrods by forcing rockers: ensure pushrods seat properly; if a pushrod is damaged replace it.
- Reusing old valve cover gasket: will leak oil. Always replace gasket.
- Working on a hot engine unless specified: thermal expansion leads to incorrect lash.
- Removing rocker shaft assembly without marking positions: if you remove components, mark shims/rockers to their original locations if you plan to reuse them; replacement parts may be needed if worn.

Troubleshooting after adjustment
- Loud clatter: lash too loose → re‑measure and tighten slightly.
- Tapping disappears but engine runs rough: lash too tight → valves may be held slightly open; re‑adjust.
- Persistent oil leak at valve cover: check gasket seating and bolt torque.
- Valve burning or low compression: excessive lash or other valve damage — perform a compression/check valve seats.

When to replace parts
- Replace any pushrod that is bent, scored, or has worn spherical ends.
- Replace rockers or bushings that show play or wear.
- Replace tappets/lifters if pitted or worn.
- Replace valve cover gasket whenever you open the cover.
- If a valve is sticky, burning, or seat is pitted, perform a valve job (regrind or replace valve/seat).

Final notes
- If you don’t have the TE‑20 workshop manual, get one or a reliable spec sheet and verify clearance, torque, and firing order before beginning.
- Work methodically, one cylinder at a time, and recheck. Proper valve lash is a simple but critical tune‑up that will extend engine life and restore performance.
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