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Adjusting The Valves
On Your GS500

By Marc Malagelada Duch
GS500 owner from Girona, Catalunya, Spain

It's not rocket science or voodoo.  It's just simple measurements and a bit of math.  Doing it yourself saves you some serious cash that you can spend on other goodies for your bike.  Plus the knowledge you gain will be invaluable.

Aspect of the bike, after the seat and side covers removal.

Somebody installed a wrong battery (breather in the opposite side). The vapors coming out the battery rusted (nearly eaten) cables connectors and fasteners of the black box. Not a good spectacle to see. 

Remove the tank. Only 2 screws.
Close the cock under the tank and remove hoses.

Larger tube (right in the photo) goes to L shaped intake in petcock.
Shorter tube goes to general intake in petcock.

Remove air filter. 2 screws at each side of the frame, and 2 that will link to the carburetors.

At this time, you might want to start the bike and see how both carburetor slides work as you wind the throttle.
This will give you an idea if they are both working OK.

You might see the "slides jumping spectacle": At low rpm, when the engine sucks air, slides lift up because of the vacuum generated. As soon as valve closes the air flow, they will fall down again.

Soon you will run out of fuel.

2 screws will hold carbs to the engine intake manifolds.

Remove gas cable and choke cable.
Remove hoses coming from the petcock:

  • upper T: goes to lower part of the bike: fuel overflow.
  • lower T: fuel intake coming from the petcock.
  • vacuum tube that will automatically enable fuel to travel from tank to carbs through the petcock. PRI position does not require vacuum to let fuel reach the carbs.

Remove carbs assembly.

Camshaft to shim clearance should be between 0.03mm and 0.08mm

Remove valve cover by:

  • 1: remove head cover breather (4 screws)
  • 2: remove bead cover (6 screws)
  • Be careful with the head cover gasket. Replace if dried out. (10$)
You will need a thickness gauge to do the valve job.
It's not expensive but a little difficult to find one that will suit your needs.

You need one that will neasure 0.03mm and 0.08mm

I got that in one of these cheapo tool kits (100 tools for 25$)

Remove right "suzuki" cover and locate the R and R-T marks.

Align pick-up with R-T mark with a 19mm wrench

The marks on the camshaft should be facing one to another.
If they are one opposite to another, turn the crankcase 1 complete turn and realign pickup to R-T
With the engine at that point (see 2 last photos) measure the
gap under the camshaft lobes in all but exhaust left valve.

Slide a thickness gauge between the camshaft and the shim.
There should be a gap between 0.03mm and 0.08. If it is out of specs, replace the shim with a 0.05mm thinner or thicker.

Rotate the engine 1 complete turn to measure exhaust-left valve.

To replace shims you can use a special tool. I don't have one: I removed camshaft supports and replaced it easily.

Now it's a good time to check if camshaft chain tensioner is OK.

Remove 2 allen bolts and remove tensioner.

You will surely hear a "klatch" when you remove it: it's the tensioner that relaxed its spring.

Use a screwdriver to check that camshaft chain tensioner is working OK.
Reinstall chain tensioner:
  • Use the screwdriver to keep the spring from pushing the tensioner arm.
  • Install the tensioner.
  • Remove the screwdriver so that the spring relaxes and pushes camshaft chain


  • Check for different tensions all along the chain by rotating the engine.
  • Measure 20 links (21 pins). They should measure no more than 157.8mm (6.21inches). 
  • Reinstall head valve cover and replace gasket if dried out.
  • Reinstall breather cover. 
  • Tighten bolts securing carbs to intake manifold.
  • Reinstall throttle cable. Move steering to ensure that there is a little play in all positions.
  • Reinstall choke cable
Install air filter box. A new air filter element is about 20$. Replace it if it's dirty or too old.

Do not forget to:

  • connect petcock vacuum hose to left carb.
  • connect battery breather hose.
  • Ensure that all cables are proppery routed through the frame.
  • Ensure that breather hoses are routed to floor (canister in California), except valve cover breather that goes to air box.

If I had a vacuum meter, I could check if carbs are both working fine.

Reassemble everything, pull choke and crank the engine.
It should start and you will need to reset idle screw (middle of the carbs) to set it up to 1200RPM

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Last modified: March 15, 2006