Carburetor Maintenance

The Carburetor
Love it or hate it, it may well dominate the time you spend working on your motorcycle. A well-maintained carburetor makes for a good-running motorcycle and a happy motorcyclist. A poorly-maintained carburetor makes for a motorcycle that runs like shite or not at all, and a very sad motorcyclist.

Carburetor cleaning is needed when contaminates cause one or more of the very small orifices in the jets to be partially or completely obstructed. If the bike is stored for a prolonged period, without either completely draining the carbs of gas, or not using a gasoline stabilizer like Stabil, gum will form from the gasoline breaking down. This gum will then clog the jets. Another source can be rust from the inside of an old tank or contaminates in the gas. A fuel filter will help prevent contaminates from reaching the carbs.

If a bike is properly winterized and a fuel filter is installed carburetor problems can usually be prevented. Running a tank with a fuel system conditioner like SeaFoam added occasionally can be helpful as a preventative measure.

The rubber fuel and vacuum hoses degrade over time, becoming hard and less elastic. Replacement hose can be purchased from an auto parts store for only a few dollars. Replacing these at the same time as the carburetor cleaning is recommended to prevent future problems and make it easier to install and remove the tank. Newer hose will slip on and off the petcock easier and seal more tightly.

Carb rebuild kits are available that contain replacement rubber seals and jets.

What's What?
Carburetor drains and drain nipples are in RED.

The Idle Adjustment is in BLUE.

The Pilot Screws are in GREEN. Image courtesy of xDaveManx

Cleaning and Removal
Cleaning and removal section by Dalemac as transcribed from his article: Full Carburettor Cleaning & Coolant Drain and replacement tutorial (with pics). [Forum article unavailable]

Forward
"Hi People! I have taken quite a bit from this site over the last month or so, so now it is my turn to give something back. Seeing that Sean could not complete his guide, i have prepared a similar guide myself, i hope you all find it useful! I recently conducted a full overhaul of my carbs, including a coolant change. I hadn't planned on doing this, but an o-ring in one of the coolant header pipes decided it didn't want to seal anymore so i decided to do the carb clean anyway and document it to explain to the people here who don't know how the job is done. I photographed this extensively and have now written a 'how to' guide to help others complete this relatively easy but necessary task."

Disclaimer
This is a guide and i cannot be held responsible in any way for any loss or damage of anything or everything! You follow the guide at your own risk and cannot hold me responsible in any way shape or form. ALWAYS read the labels of any product in full before using them, adhering to all safety recommendations and warnings.

Role of the Carburetor
The carburetor's job is to mix air and fuel and supply the mixture to the engine. Often problems can arise when a carb'd bike has sat for long periods of time, when the fuel goes off, leaving a shiny residue in the jets, other holes and other internal surfaces of the carburetors. I first conducted a carb clean when i bought my gpz as it kept dropping onto the right cylinder only, when at tickover, and would only pick up the left cylinder at around 7k rpm. after the clean it ran sweet and hasnt caused me any problems since.

Overview
Lets get started! TIPS: Lefty loosy righty tighty (how to remember which way you turn a right threaded screw, bolt or whatever) left = anticlockwise and loosening Right = clockwise and tightening I have split the guide down into the following tasks: NOTE: I live in the UK and our version of the EX500 has heated carbs which basically draws coolant into the carbs to keep them warm. Some models may not have this feature, and if your bike does not have this feature there is no need for you to drain and replace the coolant, unless you want to!
 * 1) Tank removal
 * 2) Coolant drain and rinse
 * 3) Carb removal
 * 4) Carb dis-assembly and clean
 * 5) Carb assembly and pilot screw adjustment
 * 6) Carb installation
 * 7) Coolant refill
 * 8) Tank installation
 * 9) Start-up and test

Task 1 - Tank Removal
You will need:
 * Phillips screwdriver
 * 12mm socket and wrench
 * Pair of pliers

Step 1
Take your beloved ex500/ gpz500. Using the Phillips screwdriver, undo the two fairing screws located on each side of the fairing which connect the front fairing to the tank.

Step 2
Using your ignition key, remove the seat. (shouldn't need a pic for this i hope!)

Step 3
Locate the petrol tap on the left hand side of the bike. Turn the switch to ensure the flow of petrol is in the "Off" position. (as shown in pic)

Step 4
Locate the two rubber lines connected to the petrol tap. (as shown in the image above) Use pliers to remove the lines from the petrol tap. Be careful when doing this as there will still be petrol in the fuel line, which will come out when you disconnect the line.

Step 5
Locate the main tank bolt under the seat. use your wrench with a 12mm socket anticlockwise (lefty loosy righty tighty) and remove the bolt.

Step 6
Remove both rear plastic lugs from the tank mounts. This is simple, pull the fairing away from the tank until the lugs pop out.

Step 7
Once you have completed the above, you can lift the tank away from the bike. If you don't want to scratch your fairing, have another person help. if this isn't possible I suggest you remove the whole front fairing unless you don't mind the possibility of a few scratches. Put the tank to one side, preferably a well ventilated area.

Task 1 complete!

Task 2 - Coolant drain and rinse
NOTE: Not all EX500 / GPZ500's have heated carbs. The EX500/ GPZ500 has the rather unique feature of heated carbs. This is achieved by taking coolant from the cooling system and passing it through the carbs, keeping them warm. This can provide a massive advantage in the winter months, when other bikes suffer from carb icing, especially if you live in a cold place such as England like me! To clean the carbs, it is best to drain the entire cooling system rather than pinching the lines to stop it leaking all over the place. coolant is cheap anyway and it could well save time in the future!

You will need: Note: Always dispose of chemicals such as coolant properly and as your local authority intends. NEVER pour coolant into a drain or down the sink - seriously. If you have any issues contact your local authority and ask how it should be disposed of properly.
 * Larger phillips screwdriver
 * 10mm socket
 * 8mm socket
 * Wrench
 * Torque wrench
 * Draining pan/ bucket
 * something to use as a container to hold and dispose of coolant safely.

Step 1
Remove the lower fairing. it is held in by two Phillips screws on the radiator (big headed ones) and two 10mm bolts on the underside of the fairing. Unfortunately i cannot show this because i managed to round off one of the underside bolts but fortunately for me it can be done without removing the lower fairing.

Step 2
Place your draining pan or bucket under the drain bolt on the right hand side of the engine as shown below. Using your 8mm socket and wrench, undo the drain bolt. hardly anything should come out at this point.

Step 3
Undo the main coolant filler cap as shown below. The coolant should now drain from the system at a reasonably high pressure. Ensure you stand well back and keep all childen and pets away - coolant smells sweet and attracts them but can have devastating consequences such as blindness or even death if swallowed, as well as skin irritations. If you haven't removed the lower fairing it is necessary to create a funnel to stop the coolant from running into the lower fairing. i made mine from an old kitchen roll tube as shown below.

Step 4
At this stage you should remove, drain and rinse the coolant reservoir. It is the big white tank located on the right hand side of the bike and is usually hidden by the fairing. i have not done this as i had only done it a few days prior, when my gpz first started leaking.

Step 5
Now you can rinse the system. the quickest and easiest way to do this is use a hosepipe in the main coolant filler hole and rinse until only water is coming from the drain hole.

Immediately transfer the coolant into your suitable storage, correctly label and hide from children and animals who might be curious and want to take a few gulps. Dispose of the coolant quickly and in the appropriate manner.

Step 6
Reinstall the drain bolt and torque to either 10nm or 12nm depending on your model.

Task 2 complete!

Task 3 - Carb Removal
The removal of the carbs is no easy feat. The carbs are wedged in between two sets of rubbers, one per from the air-box to the carbs (known as carb rubbers) and one set from the carbs to the engine (known as inlet rubbers).

You will need:
 * (Flat head screw driver
 * 2X 10mm spanners
 * some lint free cloth to place in the engine inlet rubbers

Step 1
First you will note that there a lot of cables, wires and tubes coming into and going out of the carbs. My best advice is to label each item with a sticky label to ensure you know where things go when you come to reinstall the carbs. I have labeled as much as possible in the images below.
 * 1) Push the wiring loom to one side
 * 2) Remove the choke cable
 * 3) To remove: push in on choke lever to create slack in the cable. Obviously you're choke should be closed when doing this.
 * 4) Remove the cable (including the metal portion on it) from the holder that is screwed into one of the carbs. Note that the ball of the cable is still in the lever at this point
 * 5) with the cable now loose, and you still pushing in on the lever, rotate the wire portion so that it lines up with the slit on the choke lever and push on the ball to remove the cable from the lever.
 * 6) Loosen the adjustment on both the front and rear throttle cables
 * 7) Disconnect the vacuum hose on the right carb (mine is connected to a scottoiler)

Step 2
NOTE: Not all EX500 / GPZ500's have heated carbs. Disconnect the coolant line to the left carb at the filter on the left hand side of the engine

Step 3
Disconnect the coolant line to the right carb at the connection near the clutch cable.

Step 4
Now all cables, wires and tubes should be disconnected from the carbs with the exception of the throttle cables (these are much easier to remove when out) and the carb breather hose (orangey clear one)

Step 5
Locate the two screw fasteners on each engine inlet rubber and use a flathead screwdriver to loosen them off as much as possible without actually taking the screws out of the fitting.

Step 6
Using your Flathead screwdriver, lift and push the circular springs attaching the air-box rubbers to the carb towards the air-box.

Step 7
You are now ready to pull the carbs away from the rubbers. The easiest was i have found of doing this is pulling the carbs from the engine rubbers, and then the air-box rubbers, as shown in the pictures below.

It's a lot easier if you first remove the air filter cover (two screws/bolts) and then loosen the air box (4 screws/bolts) prior to trying to pull the carbs out of the rubbers. Now use your two 10mm spanners to release any remaining tension in the throttle cables, then slide the ends of the cables through the gap on the fixture, the same as you did on the choke cable.

Task 3 complete! You should now have a carbless ex500 and a set of carbs to play with!

Task 4 - Carb Dis-assembly and clean
You will need:
 * Flathead screwdriver
 * Thin Flathead screwdriver (one which the head is flush to the stem)
 * Phillips screwdriver
 * Carb cleaner that is suitable for plastic parts (PJ1) is good if you can get hold of it)
 * Ventilated space
 * Decent face mask to stop inhalation of carb cleaner
 * A few plastic tubs you are willing to throw away
 * 8mm socket
 * wrench
 * 8mm spanner
 * A clean work surface and some news paper
 * Unlubricated air line (or pump from inflatable air bed or similar)

Step 1
Once you have removed the carbs, it is necessary to completely drain all the fuel from the carbs. This is usually done by attaching a rubber hose to the nipple at the bottom of each carb, undoing the screws and watching the fuel trickle out. Personally I prefer to just turn the carbs upside down and watch the fuel pour out of the overflow line and straight back into my tank. This saves the chance of rounding off those two screws!

Step 2
NOTE: Not all EX500 / GPZ500's have heated carbs. If, like mine, your bike has coolant running through the carbs to prevent carb icing, you will need to remove the associated lines. The best way to do this is undo the Phillips screw holding the metal plate in place, remove the gold plates, and pull the entire fixture out of the carb. WARNING: If you perform this step you will need 4 new o-rings in orter to prevent leaking. WARNING: Alternatively, you can try to remove each individual line from the fitting, but you run an even higher risk of snapping one of the very frail mounts, which will result in an entire new fitting including new o-rings anyway. But, your choice!

Step 3
Remove any other fluid lines if you have not already done so.

IMPORTANT! I recommend that you only EVER work on one carburetor at any one time. Parts from one are not interchangeable to one another, and the only way to ensure you have the correct parts are to disassemble, clean and reassemble one carb at a time. This also allows you to go back and check the other carburetor IF NEEDS BE in case you think you have gotten something wrong. Good fail-safe if you ask me, and it wont take you any more time to complete!

I have used the above method on my left carburetor, I will only show this once so you will need to repeat the process for the other carburetor!

Never use any metal instruments on the inside of the carburetor unless for the removal or installation of an object as described below. The carbs are made form very soft metal and will get scratched or dented easily, so don't be tempted to scrape away any hard to clean areas!

It is also very important to obey all safety recommendations when using carburetor cleaner. Wear a face mask, work in a well ventilated area etc. WARNING: Some chemicals found in carburetor cleaner have been known to cause things such as cancer, and birth defects to siblings. SERIOUSLY be careful what you do with this stuff. Lock it away when not in use if you have to! We will start be removing the diaphragm cover. Use your Phillips screwdriver to undo each of the four bolts securing the diaphragm cover to the carburetor. You will need to apply some pressure to the diaphragm cover as there is a spring beneath, which assists with holding a needle down beneath it.

Step 4
Removing the cap will expose the diaphragm and spring, allowing you to peel the diaphragm away from the carburettor and pull the entire top half of the internal components from the carburettor. Remove the spring from the holder, pull the holder up and remove the main jet needle. Once complete, you should have  seperate components as shown below. Check the diaphragm for holes, rips and tears. If it is damaged replace the diaphragm.

Step 5
Flip the carbs over. If your set of carbs have a plug over the pilot screws, you will need to remove this. The easiest way to do this is drill through the plate and pull it up and out, exposing the pilot screw.

Step 6
Locate the four Phillips screw holding the float bowl to the rest of the carburetor. Undo and remove these four bolts, then gently pull the float bowl away from the carburetor body and put it to one side.

Step 7
With the float bowl removed, you will be able to see several items. Don't let all this scare you it's quite an easy task and you have gotten this far!

I have labeled everything that should need to concern you! First, take the spray tube from your carb cleaner can. this should be the perfect size to push the pin out of the float, and allow you to pull the float from the carburetor.

Step 8
Using your thin Flathead screwdriver, remove the pilot jet. Nothing else should come out of this hole. Place the pilot jet into one of your plastic tubs.

Step 9
The main jet needle sits in a mounting which can also be removed from the carburetor. Unscrew the main jet from this holder, using an 8mm spanner if you need to keep the holder in place while the jet comes out. Once the jet is out, unscrew the main jet holder using the 8mm socket or spanner. Place the main jet and its holder into the plastic tub.

Step 10
turn the carburetor upside down, and look in through the largest hole, you will see the little gold piece, simply push this out with your finger so it falls out the main jet holder hole. place this piece into your plastic tub.

Step 11
Turn the carbs over again and locate the pilot screw. remove the screw using a Phillips screwdriver, and place it into your tub. there is also a spring and and o-ring which may come out with it, put the o-ring back in and clean the spring if you feel like it. The carb is now fully disassembled and ready to be cleaned. Used the carb cleaner as per instructions on the can. Spray all internal surfaces including the float bowl and all passages and holes all over the carburetor including all jet holes and the pilot screw holes. Spray the contents of your plastic tub, and submerge for 5 to 10 minutes. Spray down each jet or holder to ensure they are not blocked and are clean.

Step 12
Once you are sure everything is clean, dry the inside of the carburetor. This is best done with an unlubricated air line. Also use the airline to force air down the jets and make sure they are clear. Dry all components in this way. Task 4 complete!

[TODO: task 5-9]