Step by Step Motorcycle Valve Adjustment PLUS WHY Not Just How...

Motorcycle Valve Clearance Adjustment Explained

Introduction to Valve Adjustments

• The speaker introduces the topic of valve clearance adjustments in motorcycles, emphasizing its importance and complexity.

• The speaker highlights that unlike cars, motorcycles require periodic removal of the valve cover for inspections, which is often overlooked by owners.

Importance of Regular Inspections

• Manufacturers recommend inspecting and adjusting valves every 4,000 to 26,000 miles, leading to additional costs for maintenance.

• A cursory inspection can be performed without removing valve covers or camshafts; this approach is encouraged for DIY enthusiasts.

Compression Testing Insights

• The speaker discusses a specific case involving a 2013 Kawasaki KLR650 with low compression readings (74-75 PSI).

• Initial confusion arises from low compression; the speaker explains how adding oil can help achieve a more accurate reading during cold engine tests.

Understanding Compression Readings

• After adding oil, compression improves to around 90 PSI but still indicates potential issues within the engine.

• To obtain true compression readings on this model, the valve cover must be removed and a special procedure followed due to its unique compression release feature.

Evaluating Engine Health

• A final reading of 135 PSI suggests that while the engine is operational, it may not be performing optimally compared to expected values (around 150 PSI).

• Low compression could indicate problems with valves; thus, conducting a compression test before opening up an engine is recommended.

Reasons for Frequent Valve Inspections

• The necessity for regular inspections stems from higher compression ratios in motorcycles compared to cars.

• Higher performance engines have tighter tolerances between valves and pistons, necessitating closer monitoring to prevent mechanical failures.

Understanding Valve Adjustments in Motorcycles

Importance of Valve Functionality

• A minor issue, such as an intake valve not opening fully by a tenth of a millimeter, can lead to noticeable performance loss in motorcycles due to their smaller displacement and limited power.

Differences Between Motorcycle and Automobile Engines

• Most automobile engines utilize hydraulic tappets for automatic valve lash adjustments, while motorcycle engines often have direct cam-to-valve contact without hydraulic cushioning.

• Some older or performance Japanese car engines require manual valve shimming at intervals (typically every 60,000 miles), which is more frequent than recommended for most motorcycle engines.

Service Practices and Customer Behavior

• Regular valve lash inspections encourage riders to return to dealerships; however, many motorcycle owners prefer self-maintenance after initial warranty services.

• The speaker estimates that less than 20% of riders return for subsequent oil changes after the first service.

Labor Costs and Maintenance Insights

• Valve clearance inspections can take three to four hours of labor, with additional time required if adjustments are necessary. This creates significant revenue opportunities for service departments.

• While not suggesting a conspiracy among manufacturers or dealers, the speaker notes that frequent inspections may simply confirm that everything is within factory specifications rather than necessitating actual adjustments.

Challenges in Performing Valve Adjustments

• The speaker avoids creating how-to videos on valve services because they often involve simple checks rather than complex adjustments since valves typically remain within spec.

• Filming these procedures can be difficult due to confined spaces around the engine when it is still mounted in the frame.

Practical Demonstration: KLR Valve Clearance Adjustment

• The speaker demonstrates checking and adjusting valve clearances on a KLR motorcycle, chosen for its accessibility for detailed explanation.

Preparing for Adjustment

• Ensuring the engine is at top dead center (TDC) involves locating timing marks on the flywheel and aligning cam sprockets accordingly.

Measuring Clearances

• Once aligned at TDC, both intake and exhaust cam lobes should be positioned correctly relative to cylinder valves before measuring clearances.

Using Feeler Gauges

• Starting with the maximum specified clearance gauge blade helps determine gaps between camshaft lobe and valve; different values exist for intake versus exhaust valves based on manufacturer specifications.

Valve Clearance Adjustment in Motorcycles

Understanding Valve Clearance Changes

• The gap between the camshaft and valve can be measured using two feeler gauge blades simultaneously, allowing for precise adjustments. It's essential to document which cylinder and valve location is being measured.

• Valve clearance changes are primarily due to engine wear affecting components like the camshaft, valve bucket, or shim. As the engine warms up, parts expand, necessitating a minimal gap for optimal performance.

• Engineers design engines with an allowance for thermal expansion; without proper clearance, pistons and valves may collide, leading to severe damage. Excessive clearance can also hinder performance by restricting air and fuel flow into the combustion chamber.

Effects of Engine Temperature on Valve Performance

• Typically, valve clearances tighten over time as the valve seat degrades, causing valves to recess further into the head when closed. This degradation is accelerated by exposure to hot gases.

• Allowing engines to warm up before high RPM use reduces wear on valve seats. A warmed-up engine performs better than a cold one because it maintains appropriate gaps between components.

Measuring Valve Clearances

• When measuring clearances, resistance should be felt when inserting feeler gauges under the camshaft; if they do not fit at all or require excessive force, adjustments are necessary.

• The correct feeler gauge size was determined to be 0.05 millimeters after testing various sizes against the camshaft's clearance.

Adjusting Valve Shims

• If minimum specified feeler gauge blades fit but maximum ones do not slide under easily, it's advisable to adjust shims down one size for increased clearance.

• Tight valves lead to low cylinder compression; thus accurate measurement of all four valves is crucial before proceeding with shim replacement.

Removing Camshaft for Shim Replacement

• To replace shims effectively, removing the camshaft is necessary. Care must be taken not to disturb timing marks during this process.

• Marking chain links with paint ensures that reassembly aligns correctly with original timing positions while preventing movement of crankshaft and pistons during disassembly.

Disassembling Components Safely

• The first step involves removing the cam chain tensioner followed by unbolting other components like journal caps and splash guards while securing the chain with zip ties.

• For certain models like KLR 650, some mechanics can replace shims without full removal of camshafts; however, complete removal is often required in multi-cylinder engines where shims sit beneath buckets.

By following these guidelines on measuring and adjusting valve clearances in motorcycles, riders can maintain optimal engine performance and longevity.

How to Properly Install Valve Shims

Extracting and Handling Shims

• When extracting shims from the cylinder, it's crucial to use a strong magnet to prevent them from falling. This ensures that the shim remains in place during extraction.

• Each shim has a thickness measurement in millimeters, which should be recorded alongside the clearance measured for each valve.

Calculating Required Shim Size

• To determine the new shim size, add the original shim thickness to the measured clearances and subtract the minimum specified clearance from the factory shop manual.

• After calculating, find the closest available shim size by checking against both minimum and maximum allowed clearances.

Installation Process

• Before installing new shims, clean gasket surfaces thoroughly to avoid introducing debris into the engine.

• Install shims in their designated positions and carefully align camshafts with sprockets before securing them according to torque specifications (12 Newton meters or 106 inch-pounds).

Verification of Clearances

• After installation, recheck valve clearances to ensure accuracy. Confirm that all calculations were correct by testing fitment of shims against specified measurements.