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Discussion Starter #1
I own a 1982 KZ1100 Spectre that I bought new. It has 10,000 miles on it. It has always been garaged and well taken care of. It has always performed flawlessly until one day this fall. It had been a week since I had last ridden it.

The engine starts and idles normally. If I open the throttle at all with the choke half on, the engine dies. If I turn the choke off even after the engine is warmed up, the engine dies. If I open the throttle with the choke fully on the engine revs up to 2,000 to 3,000 rpm and stays there even after the throttle is closed.

I spoke with my local Kawasaki dealership mechanic about it and he guessed that the carbs were gagged with varnish or dirt and should be cleaned. I asked if the vacuum switch valve could cause the problem and he said no.

I drained the gas out of each carb into a glass container and confirmed that there was no dirt or water present. I tested the gas and confirmed that there is no ethanol in it. I then removed the carbs, removed a bowl, and found it to be clean as new with no varnish or build up of any kind. The vacuum pistons attached to the needles all move freely. I am skeptical that varnish or dirt could cause all 4 carbs to fail at the exact same time.

Has anyone here experienced this condition? If so, what was the fix? Any ideas?
 

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If your bike has CV(constant velocity) carbs, try this:

I found this the other day concerning carb diaphragm problems.

Carburetor diaphragm repair that works.

Ok so your old bike's carb diaphragm has a little pinhole in it, or you've got a little tear like mine does from being old and maybe a backfire or something. So you go to the dealership or check online and you can't find a replacement anywhere. You may stumble upon services that will re-diaphragm any old carb slide, but the wait time is a month and you can't afford the 170 bucks a piece. Never fear, I have found a solution.

Carb diaphragms are made of nitrile rubber and so are nitrile gloves (big surprise right) so I experimented on several gloves with various adhesives that I thought might work and eventually I found one.

First up was liquid electrical tape. The liquid electrical tape bonded the glove together really quick and held pretty **** strong. Much stronger than needed for a diaphragm. I then tested its resistance to Gum-out (which you should NEVER use on CV diaphragm carbs btw!) and the gumout dissolved it quick. Gumout also slackened and ate through the gloves after several minutes. Well scratch that one, I wanted something that would stand up to gasoline and the occaisional capful of cleaner.

Next up, weather stripping adhesive. This was a good candidate because it seems to hold soft rubber very well for nearly forever. Same problem as the liquid electrical tape. They both smell similar as well which might indicate the solvent being usedm which is easily cut with gumout. I would imagine that xylene and lacquer thinners would have the same effect. I know after painting with nitrile gloves (urethanes, lacquers, clear coats) that the gloves are resistant but will eventually break down anyway. This reinforces the NEVER USE CARB CLEANER SPRAY IN A CV CARB advice.

On the third try, and after reading some industrial adhesives literature, I came across a family of adhesives that include regular super glue, and polyurethane adhesives. You may know the polyurethane adhesives under "Gorilla Glue" or Elmer's "Probond". These guys have di-isocyanates in them and can be particularly nasty, but cyanoacrylates and di-isocyanates are one of the only suitable bonding materials for nitrile rubber, or even hydrogenated n butyl rubbers (the green o rings used in r134 ac systems). And speaking of HNBR (the green rubber), I wish people would push keihn and mikuni and the like to use that stuff in carbs. When you look at what they resist and the temps and pressures they resist, they are CLEARLY the choice for using in a nasty gasoline / solvent environment especially where there is heat involved.... But I digress. So gorilla glue is your best bet. Superglue cures too stiff, and will degrade over time with humidity (crazy huh?). The gorilla glue, being a polyurethane and using the chemicals it does to react with the bonded surfaces, won't let go even when covered with gasoline or carb cleaner. It remains somewhat flexible, but of course is much stiffer than your diaphragm which is just a nitrile rubber coated cloth. You can apply it thinly over tears and cracks and holes and it's not going to let go.

Alternately, some people say that the spray tool dip available from napa auto parts works like a charm. The only problem here is you are increasing the thickness of the diaphragm and that will decrease the response rate of the slide. It's not that big of a deal to get by but still... The main concern is keeping the hole closed #1, and keeping it airtight #2. You could always use a small bead of gorilla glue to hold a tear closed and spray rubber over it for added protection. You could even gorilla glue some nitrile rubber glove over a larger tear. But as I said, response rate will be affected. If you think about it though, there are big springs which hold the slide down, and the suction is really what makes them rise, so as long as they still slide up and down relatively well, and are sealed you should be fine.

The bottom line is, this fix will cost you under 10 bucks and get you going in 24 hours. While you ride on it, look for a new diaphragm, or better yet, save up some money for a set of VMs or something that doesn't use those ?!!&# diaphragms!
 

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For carb cleaning:
Carb Cleaning 101

By M. Shively

The elements of internal combustion engines are: correct fuel/air ratio, spark at right time, and adequate cylinder compression.

There are many passageways and openings to check and clean. All are important in function and when obstructed or not working properly, have subtle to radical effects on engine performance. Vacuum leaks and carburetor synchronization also effect performance and should be inspected and adjusted following the below procedures.


Warning: Remove all rubber parts before you begin. These parts usually include vacuum diaphragms, needle valves, o'rings, hoses, and other parts. Spray cleaners will damage these parts. Do not disassemble individual carbs from the carb bracket.

Air & Fuel Passageways: Trace and learn individual fuel and air circuits from beginning to end. Machines can only drill straight through the cast passageways. To change direction, another angled passageway must be drilled. The union is plugged with a brass or bronze bead. Inspect and clean each passageway with spray cleaner, brushes/pipe cleaners/etc, and compressed air. Remove any discoloration and debris. Look for spray cleaner to exit from one or more passageways.

Jet Cleaning: Inspect jets by holding to light and look through them. You should see an unobstructed round hole. Clean the jets with one or more of the following: jet cleaning wires, soak solutions, carb spray cleaners and compressed air. Re-inspect jets after cleaning and install when clear of obstructions. Some main jets have paper-like gaskets. Most have metal spacers between the jet and the emulsion tube. Some screw directly into a brass emulsion tube which is machined for a 7mm wrench at its float chamber exposed base.

Inlet Fuel Valve: Inspect the needle valve & spring. Press down the tiny metal rod that protrudes from the butt or float end of the needle valve. The spring should move freely and return the rod to its location. Check the needle valve's seat area for a groove or other wear. It should appear highly polished. Some needle valve seats are rubber and wear may not be visible. Inspect the needle valve jet seat. You can clean the jet seat with Q-tips and semi-chrome polish if necessary.

Carb Body Castings: Blow air through the atmospheric vent holes located on the dome of each float bowl chamber. Air should exit via hoses or brass nipples. Inspect the emulsion tubes and passageways (cast towers that jets thread into) for discoloration and debris. Clean interior emulsion towers with a soft bristle gun cleaning brush. Clean each Venturi (main carb bore).

Needle Jets & Jet Needles: Clean the needle jets, jet needles, and passageway or tower that needle jet screws into. Clean the emulsion tube (pipe between needle jet and main jet) (Main Jet may screw into emulsion tube). Jet needles are part of the throttle slides. See below…

Throttle Slides: There are several types of throttle slides: Mechanical linkage, vacuum, diaphragm, and cable. Disassembling the jet needle from the slide is not always required for cleaning. If you have vacuum piston type throttle slides (large diameter solid metal slide), avoid cleaning the lubrication from sides and caps. If piston type check cap vents and passageways with air. Clean if necessary and re-lube. If you have rubber vacuum throttle diaphragms, inspect for dry-rot, defects, and tears by gently stretching rubber away from center. Do this until all areas around diaphragm have been inspected. Replace any defective part as described above. Clean carb body areas around diaphragm including air passageways and air jets. Diaphragms have a locator loop or tab fabricated into their sealing edge. Observe this locator upon reassembly. Avoid pinching the diaphragm when reinstalling caps.

Fuel Screws: Fuel screws have sharp tapered ends. Carefully turn one fuel screw in while counting the turns until it seats lightly. Warning: These screws are very easily damaged if over tightened into their seats. Record amount of "turns-in" and remove the fuel screw, spring, washer, and o'ring. The fuel screw is part of the enrichment (choke) circuit...clean passageways as described above. When carbs are assembled, spray low PSI compressed air into diaphragm air vents located at intake side of carbs. Throttle slides should rise, then fall when air is removed. Lightly lube external moving linkages. Reinstall carbs and follow through with carburetor synchronization.

Throttle Cables: Lubricate cables periodically. If cables are disconnected from carbs or removed for replacement, etc . . . remember cable routing and ensure proper reinstallation routing. Avoid bread-tying, sharp bends, and pinching cables. Adjust cables so throttle grip has about 5mm of play or throttle slides or butterfly valves may not open completely (full throttle)(wide full open).

Float Bowls: Inspect float bowls for sediment, gum or varnish, crystallization, and defects. Clean all pipes, tubes, passageways, and embedded jets with cleaners and compressed air. Remove and clean the drain screw and area. Inspect bowl gasket and replace if necessary. Clean and inspect overflow pipes and tubes, look for vertical cracks.

Floats: There are several types of float materials: plastic, brass, black composite, tin, and others. Handle floats carefully. Avoid bending, twisting, denting, or other means of mishandling. Most floats are adjustable by bending a small metal tab near the float axle end. Do not change the float adjuster tab unless tuning fuel service levels. Clean metal floats by soaking or by spraying cleaner and wiping clean. Other material type floats may require replacement if cleaning is necessary. Inspect the needle valve (float valve) and seat. Check needle valve's spring loaded pin. It should depress and return smoothly and without resistance. Check the needle valve's tip for a worn groove. Replace needle valve and seat if either symptom exists. These parts wear together and must be replaced as a set.

Synchronization: This is a fine adjustment performed usually and preferably with the carbs installed and the engine running. The unusual part is performed with gauged wire with the carbs on the work bench. Carburetor synchronizing balances Venturi vacuum at the exhaust side of each carburetor, resulting with smooth idling and optimized performance at all throttle openings. Synchronization is checked using a set of gauges which are either air vacuum type or liquid mercury type. The gauges are connected to vacuum ports on the intake manifolds via nipple tubes or if sealed with screws, sync gauge adapters will be needed. With the engine running at temperature, and with a fan or means of forced convection aimed onto the engine, the carbs fuel screws and idle are adjusted, then the synchronization is adjusted via adjustment screws on the carbs. A reserve fuel tank is recommended for convenience of accessing carbs during this procedure. See gauge instructions and repair manuals for detailed use of synchronization gauges.

Notes: While carbs are apart, record the jet sizes. Look for a very small number imprinted on the body of the jets. Verify that numbers are the same for all jets on models with in-line cylinders. A few transverse-4 models and V-engines, the inner and outer carbs use some different size jets and it's important to not mix them up. If you have dial or veneer calipers, measure and record float heights. Perform measurements with floats just touching needle valves, though not depressing the needle valve rods. Replace fuel and vacuum hoses. Be sure to use fuel rated hose for fuel. Install or replace in-line fuel filters. It's a good time to remove and clean interior petcock fuel filters. Inspect carb manifolds for dry-rotting, inspect all clamps and air ducts. Inspect, clean, lube, and/or replace air filter(s).
 

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Discussion Starter #6
Thanks for all the info guys. The GSResources link was very helpful.

I completely disassembled the carbs today and found that the pilot jets were all clogged. As small as the orfice is (about .014), I'm quite surprised that it took 27 years for them to get gagged. I cleaned them out using a strand from a wire brush then soaked them in Berryman Chem-Dip carb cleaner. They are clean as a whistle now. Everything else in the carbs was clean and looked like new.

I did an internet search for Mikuni pilot jets and found a great webpage by Ian Williams Tuning in Australia titled "Mikuni Motorcycle Carburetor Theory 101". Here is the URL Mikuni carburetor operation and tuning It helped me understand how the carbs work and gave me confidence that I had found the problem.

Unfortunately, one of the bowl gaskets tore and I had to order a replacement ($16) from my local dealer. It will take a week to get it so it will be awhile before I can report back to confirm that this fixed the problem.
 

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While you have the carbs off, blow some carb cleaner through the pilot jets and make sure you see it coming out in the throat of the carb. That way you know the passage way is clear also. Blow some compressed air through after you finish checking it to get all the cleaner out.
 

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Discussion Starter #11
Thanks StarGate for the reminder about the passage way between the pilot jet and the carb throat. I was trying to figure out how to remove the plugs covering the pilot needles so I could clean them and the passage. It was easy enough to remove the sealer on top of them but I'm not sure how to get them out. The factory shop manual instructs to punch them and pry them out with an awl. Has anyone done this or found a better way? The manual mentions that these plugs are only used on U.S. models so I presume that they don't really need to be replaced. They appear to be meant to discourage changing the emissions settings.

When I spoke with my local dealership mechanic he told me that these bikes run better if the pilot needles are screwed out 1/2 turn to enrichen the mixture.
 

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Take a small drill bit, (a size smaller than the screw you intend to use) and slowly/carefully drill a hole in the plug. The plug is thin so this won't be difficult with a sharp bit. The mixture screw is just below the plug so don't let the bit slip or go to deep or you could hit the screw and damage it. Once you have the hole in the plug, insert a metal screw into the hole and just snug the screw. Grab the screw with a pair of pliars and pull it straight up and out and the plug will come out with it. Don't worry or over think the drilling process, just use light pressure and low rpm and you'll be fine.
 
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