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GT Valve Lash Adjustment
Overview
This procedure directly applies to all Vespa/Piaggio water cooled LEADER engine applications (125CC 4V L, 200CC 4V L). Specific disassembly/assembly instruction and tips are based on Vespa GT construction. Other Vespa/Piaggio models may require their own specific chassis disassembly/assembly instruction, but all engine disassembly/assembly instruction is common to the Vespa/Piaggio water cooled LEADER engine.

Time Required: 3 hours
Skills Required: Use of hand tools (screw driver, fixed wrench, socket driver, feeler gauge)
Degree of Difficulty: Moderate
Parts required: None
Preparation
You need to set the valve lash on a cold engine. Let the scooter sit overnight.
Procedure
You don't need a special tool to remove the clutch shaft nut, or to hold the clutch stationary. Remove the clutch shaft access cover from the transmission cover. Use an ordinary wrench to remove the clutch shaft nut as a helper holds the scooter upright, applying the rear brake, with the rear wheel resting on the ground.

You need to select a method to rotate the engine, such that the cylinder head is raised up and into the under-seat access area. Take your pick of Method A, or Method B.

Method A:
Remove the exhaust
Remove the right rear wheel support arm
Remove the rear wheel
Remove the lower bolt from the right rear shock absorber
Unbolt the airbox from the engine and move it to the side
Remove the lower bolt from the left rear shock absorber

Method B:
Place a 2x4 under the center stand
Disconnect the left and right rear shocks by removing the nuts at the top of the upper shock studs
Unbolt the airbox from the engine and move it to the side

Place a floor jack directly under the engine swing-arm, and raise it as far as you can go before the front wheel leaves the ground. As you raise the jack, the engine will rotate on the swing-arm pivot, in the desired direction. see illustration



Remove the transmission cover
Remove the valve cover
Unplug the spark plug high tension wire from the spark plug

Now you'll need to rotate the engine, to top dead center (TDC) on the compression stroke. Using a wrench on the variator shaft nut, rotate the engine counter-clockwise to align the camshaft sprocket 4V mark with the reference mark on the cylinder head. **NOTE** This cam gear is shared by smaller 2V Vespas as well, so there are two different marks on the gear. If you can see the arrow but can't read the "4V" stamp, you may possibly be on the 2V mark, putting cam pressure on the lifters, and giving a bad clearance measurement. The 4V arrow will be pointing straight up (vertical), when it's aligned with the reference mark. Use an inspection mirror and penlight to view the camshaft sprocket 4V mark and reference mark. see illustration



With a screwdriver in the adjustment screw slot, loosen the lock nut. Slide the feeler gauge under the adjustment screw, and turn the screw until you get a slight drag on the feeler gauge. While holding the screwdriver stationary, tighten the lock nut. Double check the lash with the feeler gauge to make sure it didn't shift when tightening. Keep in mind that it's best to be slightly on the loose end of the spec rather than the tight end. If moderate effort is required to slide the feeler through the gap, the adjustment screw needs to be loosened.see illustration

The GT200 valve lash specifications are:
intake 0.004in (0.10mm)
exhaust 0.006in (0.15mm)



Refit all parts in reverse order of removal
Copyright 2006 Gary (DBA Addicted) All Rights Reserved
Last Updated Sat Jun 05, 2010 6:53 am
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