Scorpa SY250F Valve Clearance Adjustment Manual

Adjusting / Shimming Valves

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For years, the valve trains used in most four-stroke dirt bikes have been the tried and true rocker-arm setup. Honda has used this setup on the XR line for years. With engines like the XRs and DRs that are not high-revving, high-output motors, this setup works just fine. But as the new four strokes become more and more advanced, the need for a better valve train is needed. The bucket-under-shim setup will allow higher and quicker revs and is a more reliable, because it has less mov�ing parts. To put it simply, rocker arms (XR, DR, XT) are Model T and the bucket under (YZF, CRF, DRZ, KLX) are F-1. Make sure that the bike is clean. Take the tank off and clean the backbone of the frame. The motor needs to be cold and not run in the past 12 hours.

Step 1-3: Aligning Cams

Remove the plugs on the ignition cover. The large hole will allow you to turn the crank and the small hole is how you line up the timing marks at top dead center (TDC).
When the timing mark is lined up on the flywheel the marks on the cam gears will be lined up with the too of the bead. To double-check yourself, the cam lobs should be facing out.
If you cannot get things to line up, you could have one of two problems. The cam gear can spin on the shaft. And the cam chain can stretch.

Step 4: Measure Valve Clearance.

Using feeler gauges, check your valve adjustment. Step 5: Write down the measurements.

Step 6-10: Disassemble Valve Train.

Now we need to start disassembly of the valve train. Loosen the 10mm bolt in the chain tensioner before removing tensioner from cylinder.
You will need to remove the decompression shaft on older YZFs.
Stuff a rag In the camchain opening.
Remove the cam caps. The cam bearing keepers are the reason for the rag being stuffed in the opening. They can fall in the motor and cause some retrieval trouble.
You can use a shop rag, or other method, to keep tension on the cam chain so it will stay on the bottom sprocket

Steps 11-14: Removing and Measuring Shims

This is the bucket and shim. Most of the time the shim comes out with the bucket.
Lay the buckets out to make it easier to keep track of which one goes where.
Measure the shims. Shims have their size stamped on them but always double-check.
Using the measurements made earlier, make the proper adjustments. The owner's manual has a data sheet that tells you the proper shims to use.

Step 15-18: Reassemble.

Use assembly lube on the cams and buckets when reassembling.
This photo shows the new shims in place. Note that the shims have the numbers facing up.
Reinstall cam caps and torque to proper specs (7.2 foot/pounds).
Retract the cam-tensioner adjuster and reinstall. After installing the tensioner, release adjuster, then tighten cap bolt (5.1 foot/pounds) and replace valve cover and plugs in ignition cover. Replace tank and clean air filter.