PRE-OPERATION NOTES: PLEASE READ THROUGH THE ENTIRE PROCEDURE BEFORE STARTING. THERE ARE SUGGESTIONS AND TIPS THROUGHOUT THE GUIDE. IT’S BEST TO KNOW THESE AND THE “NEXT” STEP BEFORE WORKING ON THE CURRENT ONE.
This preventative Maintenance “fix” is applicable and recommended for all year and model year DRZ 400 from 2000 to present.
NOTE: This How-To guide is just that, a guide. It does not replace a service manual, general mechanical knowledge, specific motorcycle repair experience, and good old common sense. With the proper tools, some general experience, and this guide, most users will be able to successfully check valve clearances and, if required, replace shims to adjust the valves to service specifications. As always, if after reading through this guide, you do not feel capable of performing this maintenance task, STOP. Ask questions on forums, take pictures of your point of confusion, and get your answers before you start.
I. Tools and Preparation
1. Essential Tools: Basic Metric Hand Tools
- 3/8 Drive socket set, 10mm to 17mm
- Allen key set 5mm to 15mm
- Wrench set 10mm to 17mm
- Feeler gauge set that covers up to 0.30mm
2. Suggested Tools for Convenience
- Magnet on a stick (retrieving shims and parts)
- Digital camera (documenting steps)
- Pen and paper (taking notes of measurements and shim sizes)
3. Preparation Steps
Before you begin, you will need to remove several components to access the valve cover and related parts. This includes the seat, tank, timing sight plug on the left cover, crank access plug on the same cover, spark plug, and valve cover. If adjustments are needed, you’ll also be removing the cam chain tensioner (CCT) and cam caps. Measuring the clearance involves checking between the bucket and cam, reading the shim size (often faintly printed), or measuring it with a micrometer. This list is not exhaustive; it covers the basics. If the steps outlined above seem beyond your comfort level, it’s crucial to STOP. Seek help from a knowledgeable friend or take your DRZ400 to a professional shop.
Cleanliness is paramount when working on your engine. Since you will be opening up the valve cover and left side cover, ensure the bike is thoroughly clean. Dirt and debris can easily enter the engine. Clean and degrease the areas around the valve cover and left side cover to create a clean working environment.
Ensure the engine is cool to the touch before starting the valve check. Working on a hot engine is dangerous and can lead to inaccurate measurements.
4. Step-by-Step Removal
- Clean the bike thoroughly: Wash and degrease the engine area, especially around the valve cover and left side cover.
- Remove the seat and tank: Detach the seat and fuel tank and set them aside in a safe place.
- Prepare the spark plug well: Remove the spark plug boot and use compressed air to blow out any debris from the spark plug well. Optionally, squirt a bit of brake cleaner and blow it out again with air. Do this from both the drain hole side of the head and down the spark plug well. If you don’t have compressed air, brake cleaner alone is a less effective alternative.
- Remove the crank access plug: CAUTION: This plug is often overtightened, making removal difficult. (Refer to footnotes for tips on removing a stuck or damaged plug).
- Remove the timing window plug: Locate and remove the timing window plug on the top of the left engine cover.
- Remove the spark plug: Unscrew and remove the spark plug.
- Remove the valve cover: Unbolt and carefully remove the valve cover.
Congratulations! You have now successfully prepared your DRZ400 to check the valves.
II. Setting Timing and Checking Valve Clearances
1. Setting Top Dead Center (TDC)
To accurately check valve clearances, you need to set the engine to Top Dead Center (TDC) on the compression stroke.
- Locate the timing index mark: Turn the crankshaft using a socket on the crank access plug.
- Align the index mark: Rotate the crankshaft in the normal forward direction until the timing index mark on the flywheel aligns in the center of the sight window. Note: Ensure you are aligning the index line, NOT the “T” next to it, in the center of the sight window.
- Verify cam lobe position: Looking at the camshafts from the side, the lobes should be pointing approximately at the 10 o’clock and 2 o’clock positions. If the index line is centered but the cam lobes are not in the correct position, you are not on the compression stroke. Rotate the crankshaft another full turn (360 degrees) until the index line is centered again and check the cam lobe position.
Image: DRZ400 cam sprockets at TDC, showing correct alignment and lobe positions.
With OEM cams at TDC on the compression stroke, the cam sprockets will appear as shown in the image. The #3 and #2 markings should be straight up, and the other index lines should be even with the top flat surface of the head.
2. Checking Valve Clearances
Now that the engine is at TDC and cool, you can proceed to check the valve clearances.
- Double-check timing mark: Briefly verify that the timing mark on the flywheel is still centered in the sight window to ensure the crankshaft hasn’t rotated.
- Understand service limits: The OEM service limits for valve clearances are:
- Intake: 0.10mm ~ 0.20mm
- Exhaust: 0.20mm ~ 0.30mm
- Measure clearance with feeler gauges:
- Start with any valve. Select a feeler gauge blade corresponding to the minimum service limit for that valve type (0.10mm for intake, 0.20mm for exhaust).
- Attempt to slide the feeler gauge blade between the shim bucket and the camshaft lobe.
- If the blade fits: This means the clearance is at least the size of the blade. Incrementally increase the feeler gauge size until you find a blade that does not fit. Record the size of the last blade that fit with a slight drag.
- If the blade does not fit: The clearance is tighter than the blade size. Decrease the feeler gauge size until you find one that does fit. Record this size.
- Repeat this process for all four valves, noting down each measured clearance.
The goal is to determine the feeler gauge blade that provides a slight drag as you pull it through the valve clearance gap.
3. Interpreting Clearances
- Clearances within service limits: If all measured clearances are within the specified service limits, no adjustment is needed. You can proceed to reassemble the engine.
- Clearances too tight (below service limit): You will need a thinner shim. Replacing the shim with a thinner one will increase the valve clearance.
- Clearances too loose (above service limit): You will need a thicker shim. Using a thicker shim will decrease the valve clearance.
Important Note on Valve Wear: As valves wear, they recede into the valve seat, causing valve clearances to decrease (become tighter). If you measure a clearance close to the minimum service limit, consider adjusting it now to provide more buffer before the next check. Rapidly decreasing valve clearances indicate valve face wear, signaling the need for a valve job soon.
III. Removing Cams and Adjusting Valve Clearances
Adjustment is only necessary if valve clearances are outside the OEM service limits.
1. Cam Removal Preparation
- Ensure TDC position: Double-check that the engine is at or very near TDC on the compression stroke.
- Remove Cam Chain Tensioner (CCT): Locate and remove the CCT. If you have an Automatic Cam Chain Tensioner (ACCT), ensure you reset it before removal.
2. Removing Cam Caps and Cams
- Loosen cam cap bolts: Using an Allen key, gradually loosen each of the cam cap bolts in a criss-cross pattern. Note the position of each bolt as there are two different lengths: two long and six short. Mixing up their positions during reinstallation can damage the threads in the cylinder head.
Image: DRZ400 cam cap bolt positions, highlighting the location of longer bolts.
- Remove cam caps: Once all bolts are removed, carefully lift off the cam caps.
- Remove cams: Lift the camshafts out, carefully maneuvering them to disengage from the cam chain sprockets. As you remove the cams, secure the cam chain to prevent it from falling into the engine case. Use a long spring, piece of wire, or zip tie to suspend it. Caution: If the chain falls, retrieve it with a hook before turning the crankshaft to avoid potential damage to the Drz400 Chain Cam Guide Touching Chain Size components and other internal parts. While the chain cannot fall too far, forcing the engine with a jammed chain can break the lower cam chain guide mount.
- Access valve buckets: With the cams removed, the valve buckets are now accessible. Use a magnet or a valve lapping tool (suction cup) to carefully remove each bucket.
- Handle shims with care: CAUTION: The small shim (9.48mm diameter) sits on top of the valve stem under the bucket. It may stick to the bucket, partially come out, or stay in place. Be extremely careful not to lose the shim. If it falls into the engine, retrieval can be time-consuming and may require significant disassembly. Stuffing clean, lint-free rags into the open areas of the head before removing buckets is a good preventative measure.
3. Determining Required Shim Size
- Identify current shim size: Once you have removed the shims, read the size markings on each shim. These markings can be faint. If necessary, use a micrometer for accurate measurement. Note down the size of each shim and its original valve location.
- Calculate new shim size: Using your measured valve clearances, the current shim sizes, and the desired clearance (ideally in the middle of the service range), calculate the required thickness of the new shims.
Example Calculation:
-
Intake Valve Example:
- Measured clearance: 0.05mm
- Current shim size: 2.50mm
- Desired clearance (mid-spec): 0.15mm (Service limit: 0.10mm – 0.20mm)
- Required clearance increase: 0.15mm – 0.05mm = 0.10mm
- Required shim change: 0.10mm thinner
- New shim size: 2.50mm – 0.10mm = 2.40mm
-
Exhaust Valve Example:
- Measured clearance: 0.25mm
- Current shim size: 2.85mm
- Desired clearance (upper-spec): 0.30mm (Service limit: 0.20mm – 0.30mm)
- Required clearance increase: 0.30mm – 0.25mm = 0.05mm
- Required shim change: 0.05mm thinner
- New shim size: 2.85mm – 0.05mm = 2.80mm
DRZ400 valve shims are 9.48mm in diameter and range in thickness typically from 2.00mm to 3.50mm. OEM shims are available in 0.02mm increments, while aftermarket shims (like Hotcams) often come in 0.05mm increments. Avoid using shims thinner than 2.00mm as they may sit too low in the valve spring retainer, causing bucket damage and potential valve lock failure.
IV. Timing the Cams and Reassembly
1. Cam Timing Procedure
Timing the DRZ400 cams is straightforward.
- Set Crankshaft to TDC: Ensure the crankshaft is set at TDC, with the timing mark aligned in the sight window.
- Install Exhaust Cam: Hold the cam chain taut and install the exhaust camshaft so that the sprocket timing marks are close to their correct position, with the lobes pointing roughly at 10 o’clock.
- Install Intake Cam: Install the intake camshaft, aligning its sprocket timing marks and positioning the lobes approximately at 2 o’clock.
- Fine-tune Cam Timing:
- Insert your finger into the CCT hole and apply slight pressure to the cam chain guide to take up slack.
- Check the flywheel timing mark and the cam timing marks.
- If a cam is slightly misaligned, remove that cam only, lift the chain off the sprocket, rotate the cam to the correct position, and reinstall.
- Repeat adjustments as needed until both cam timing marks are correctly aligned with the flywheel timing mark at TDC.
- Install Cam Caps: Once the timing is accurate, install the cam caps. Ensure the longer cam cap bolts are placed in their correct positions (refer to the image in section III.2).
- Tighten Cam Cap Bolts: Tighten the cam cap bolts in a criss-cross pattern in two stages using an Allen key. First, snug them down evenly, then snug them again to the final torque. While a torque wrench is recommended (10Nm / 88 in-lbs), especially a calibrated, quality 1/4″ drive wrench, careful tightening with an Allen key, ensuring even pressure, is acceptable if a torque wrench is not available. Caution: Overtightening can strip threads in the aluminum head.
2. Reinstall CCT and Verify Clearances
- Reinstall CCT: Reinstall the Cam Chain Tensioner (CCT). If using an ACCT, ensure it’s reset before installation.
- Verify Valve Clearances: Before final reassembly, it’s crucial to re-check the valve clearances to confirm the adjustments are correct.
- You can do this before installing the CCT by pressing lightly on the cam chain guide through the CCT hole while rotating the engine one full revolution. This helps seat the shims properly and remove excess oil.
- Follow the valve clearance checking procedure outlined in section II.2.
- Final Assembly: If the valve clearances are now within specification, reinstall all remaining components in reverse order of removal (valve cover, spark plug, timing plugs, tank, seat).
V. Conclusion and Maintenance Schedule
Congratulations, you have successfully checked and adjusted the valve clearances on your DRZ400!
Regular Valve Clearance Checks are Crucial Maintenance. Checking valve clearances against the service manual specifications and comparing them to your previous measurements should be part of your routine maintenance schedule. Adjusting valve clearances too frequently is not normal maintenance but rather a temporary fix indicating valve wear. If you find valve clearances consistently decreasing between checks, it signals valve face wear and the need for cylinder head work, including valve replacement. Re-shimming valves in this situation only provides a temporary solution. Address valve wear promptly to prevent catastrophic engine failure.
This guide aims to empower DRZ400 owners to perform essential maintenance. If you are ever unsure or uncomfortable with any step, seek assistance from experienced mechanics or consult your DRZ400 service manual. Regular maintenance ensures the longevity and optimal performance of your motorcycle.
