How to clean the carbs of an GPZ305

Unmounting

Remove tank and release all four hose clips.

Unmount the battery (first minus, then plus !)

Now You can release the air-box. Pull it back a little and You can easily get the carbs out of the frame

Dismanting

Unscrew carefully the top of the mixing chambers. Take care, a long spring is jumping out !

Very carevully pull out the vaccum-valve with its sensitive diaphragm.

Put the carb up-side-down and releaseof the floater chamber by unscrewing the 4 screws

Pull out the floater with the floater-valve by extraction of the floater pin

Now You can screw out carefully the needle-jet and the pilot-jet

Unscrew carefully the pilot adjust screw and take care not to lose the little spring and the very tiny wsher and the seal-ring.

Cleaning

Take an old teeth-brush or an old paint-brush with cutted hair; never anything made of metal.

Use vinegar for cleaning . But use it only for some minutes . If You soak it for a day or so the metal begans to corrode ! On the other hand vinegar is best to get rid any plaque (before after)

Try to blow through all holes with an air-compressor. Especially these and that.

Dont't ever try to clean holes with a wire. Use instread nylon-bristles from an old brush.

Clean everything from vinegar. Use plain water and a hair-dryer (so no acid can corrode anything)

Assembling

First softly screw in the needle-jet and the pilot-jet

Then apply the floater-valve and the floater, fix it with the pin.

Mount the floater chamber and take care not to crush the gasket.

Now carefully mount the vacuum-valve. Take special care not to damage the very senitive diaphragm. Take also attention to the location of the small clip.

Put in the spring and screw carefully the top of teh mixing chamber tight. Take attention no tto crush the diaphragm

Very slowly and carefully screw the pilot adjust screw without any force (with two fingertips)! If You feel the tip of the needle has contact unscrew it exactly 1,5 turns. It is very important that the screw is released 1,5 turns from dead block and the tip is not crushed in any way!

Fitting and rough Adjusting

For a rough synchronisation: First take a look through the carbs against a lamp and watch the flare coming through the thin gap between the throttle-plate and the wall. It should be equal on both sides. If not You can adust it with the nut and the slotted-screw in the middle between the carbs (connecting both throttle-plate-axles)

Now fix the throttle cable and shift the carbs into the frame. Don't forget to assemble the loosely the four hose-clips

First fix the carbs on the engine-side intake fittings and screw down the hose-clips engine-side.

Push the air-box forward to fit into the carbs. Screw the airbox down.

Screw down the other two hose-clips

Mount tank and fuel-hose

Fine-Tuning

Try to start the engine and fix the idle speed in the first step to 2000-3000revs. Use the black plastic throttle-stop-screw on left side (knurled screw). Let it now run some minutes to warm up a little.

Take a vacuum-gauge and adopt it to the carbs (the bigger screw below the pilot adjust screw)

Adust the carbs for equal vaccum on both sides, adjust it with the the nut and the slotted-screw in the middle between the carbs.It is important to do the adjusting on higher revs (3000-4000revs) and not on idle speed!

Hint: I used a small and old plastic bottle full of gasoline as a replacement for the tank, for I had not enough space to work on that screw if the tank is mounted, see here.

If vacuum is equal adjust down idle-speed to 1200 revs (left-side black knurled screw)

Fix everything and enjoy :-)

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