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Discussion Starter #1
Well I recently noticed that I got a gas leak coming from the carburetors :icon_frow. Also it seems to be not runnin quite up to par either like It's not geting enough fuel and when I first crank it an hit the throttle it bogs down badly an half the time will cause the bike to shut off. I have to keep messing with the throttle until finally it won't bog down but it takes alot of messin with an alot of the time it takes having the choke on in this process so it doesn't cut off. Well I ran seafoam through it a couple of times awhile back ago an it seem to clear this problem up for awhile but had it sitin awhile again due to weather and other things and now It's back again an this time the foam just aint cutin it. I did the same thing as last time and did not get the same result, I guess it was a one time deal:(! Well after takin it for a drive to see if the seafoam would do the trick again it cut off and won't crank back up and got it trailered back home. I pulled a couple plugs and boy let me tell ya they was nasty and also can tell that I know atleast one cylinder isn't geting any fuel to it. Well I went today/yesterday to get new plugs and went ahead and ordered a rebuild kit for the carburetors and hope that after changing the plugs and rebuilding the carburetors that this will fix the problem that I'm having. I bought this bike last year and it's not new by no means, it's a 88 ninja 750 and from the looks of the plugs I don't think that the people before did very much maintenance to it.:mad: So does anyone think that this will fix the problem I'm having? Either way the carbs need to be done regardless because they are leaking gas, the gas tank is nasty on the inside and when I took the fuel line off it yesterday to check on the flow it had some trash come out, when I turned the screw under the carbs to check if trash and fuel come out it came out as a trickle then a steady stream and one or 2 just barely had a trickle comin out, and when pulled a couple plugs I can tell that it wasn't getin fuel to I know atleast one cylinder. The rebuild kit won't be here till monday so till then I'm going to remove and drain the gas tank, throughly clean out the rust and trash out of the fuel tank, replace the plugs, change oil and filter( another thing that doesn't look like the previous owners didn't do), replace coolant(yet again another thing), and redo some wiring that was jerry-rigged. So do ya think after replacing the plugs, cleaning the fuel tank, and rebuilding the carbs will help with the bogging down when hiting the throttle and running badly and not geting fuel to atleast one of the cylinders that i know of?:confused: Just lookin to get some insight on things cause this is my little project bike that I am slowly going to rebuild and hope to have it back the way it should be. I know some people would just say f*** it and buy a new bike instead of putin alot of money into something like this but hey I would like to say that I built this thing and it's running like it's suppose to because of the work I put into it, just makes ya ride with more pride I guess to know your riding something you nursed back to health and built. Thanks to those who can give some insight on this and hope to hear from ya
 

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Ok first things first. Get the carbs rebuilt and cleaned(soaked for atleast 24 hrs per carb). Then like you said clean the gas tank. Then replace the fuel petcock(your fuel leak problem, they wear out about every 20 years or so. Or it is just that your floats are set too high). Then get your valves adjusted, consult a manual. Then an oil change, and finally new plugs and wires.
 

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Discussion Starter #3
The leaks isn't coming from the petcock it's coming from the carbs you can see the gas coming out them and dripping down. I will change that next though after I get these carbs rebuilt. as for adjusting the valves how's that done I don't have a manual for the bike I bought it from a guy an nothing came with it but a helmet an jacket. As for the plugs I already bought those when I ordered the rebuild kit and the wires look good almost like they been changed before but not the plugs. The oil is getting changed here soon as well. What's the soaking the carbs for? I'm a mechanic at toyota but never worked on bikes so this is a learning experience.
 

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The soaking is in a dip/cleaner for the carb bodies. Be sure to remove all non metallic parts from the carbs before you do this. It will clean all the tiny passages in the carb bodies and jets. The seafoam you used might have dislodged some accumulated varnish from the tank or bowls that has blocked the carb now. You didn't specify what model you have so no idea what valve adjustment system you have. Kawi can't make up there mind which method is best so they change it every few years it seems. If you plan on doing your own work/maint on the bike you should start surfing ebay for a shop manual.
 

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Also about the petcock. When they are faulty they leak through the carbs(they overfill the float bowls which leads to carbs leaking). A way to check is to disconnect the fuel line while on run or res(reserve), if it continously flows then it needs replaced. only time it should continously flow is on pri(prime). Since they run on vaccume pressure. If the petcock checks out then it is your floats that are outa whack.

+ 1 on the manual, man they are worth their weight in gold!!

I forgot, after you replace the petcock ensure the vaccume line from the petcock is connected to the #2 carb(it is for the vacume pressure to opperate the new petcock)
 

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A popular carb guide:

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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Can I chime in here. :) I have an 87 Ninja 750. I just rebuilt my petcock and carbs. The petcock rebuild was a cheap knock off, and I don't trust it. Not leaking now, but I still don't trust it. What happens when the floats are set too high? Too Low? After I rebuilt mine, the floats (as the carb was sitting upside down) were up very high (no "play" between the float and the needle). What are the possible problems associated with this. I readjusted them, but did so by eyeballing them.

Sorry to highjack, but the OP may end up where I am. Maybe I can save him a headache.

Also, are there any fuel valves from other bikes (manual instead of vacuum) which may fit these bikes.

Thanks guys.
 

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Float height: any one or all symptoms may happen.
Too high and fuel can overflow the bowls and leak/flood engine/fill crankcase with gas.
Too low and depending on severity, engine won't start/bogs when you open the throttle.

Float height is not the sort of thing you want to try to adjust by "eyeball". It's a very sensitive adjustment.
 

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Discussion Starter #10
The soaking is in a dip/cleaner for the carb bodies. Be sure to remove all non metallic parts from the carbs before you do this. It will clean all the tiny passages in the carb bodies and jets. The seafoam you used might have dislodged some accumulated varnish from the tank or bowls that has blocked the carb now. You didn't specify what model you have so no idea what valve adjustment system you have. Kawi can't make up there mind which method is best so they change it every few years it seems. If you plan on doing your own work/maint on the bike you should start surfing ebay for a shop manual.
sorry i got a 88 ninja 750. I just got done taking the carbs of the bike and as for the petcock i checked it and it's not leaking from that. Thanks to everyone thats been posting here it's been helpful and knowledgeable.
 

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Discussion Starter #11
Z1 Enterprises, Inc. - Specializing in Vintage Japanese Motorcycle Parts sells/can get petcock(the name for the gas tank fuel control valve). Also look at this website:Pingel Fuel Valves I understand they're pricey, but built well.
thanks man for all the information and the sites im looking on enterprises now. I got the carbs off now just waiting on the rebuild kit to get here! I can't wait to get this done so that I can ride again and see how much better it is cause I know it'll be better then when I bought it!
 

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Lemon Juice Carb Cleaning(Found on the internet)

If it was me, I'd pull the top covers off, pull the slides out, drop off the bottom bowls, remove pilots/mains. Then with the rest of the carbs still assembled boil them in some lemon juice. You'll need a big roaster pan, a little over a gallon of lemon juice (cooking supply stores), and an understanding wife/girlfriend cause the sh*ts gonna stink a little.

Boil them for about 15 minutes, then rinse them really well and blow them dry with compressed air (make sure all passages are clean). You'll be amazed at how clean they come in that short of a time.

I just did a set yesterday after hearing about it from a buddy who's used lemon juice on a couple dozen racks of carbs. After a couple of minutes at slow boil the lemon juice starts to foam up a little (careful not to boil over) and you can see all the sh*t just dissolving.

After boiling them for 15 minutes (might have to roll them around once to make sure you get the entire carbs) rinse them really well and blow them dry with compressed air. The carb bodies will be kinda chalky looking at this point. I used a toothbrush and PB blaster to put a little luster back into them and then put my internals back in.

I had pulled the bowls off, removed the floats, float needles and seats, jets, and air/pilot screws as well as the top covers and slides just to make sure no crap got itself wedged inside those passages.
After putting the carbs back together and bolting them up not only do they look great but the bikes running MUCH better with all the jet passages finally cleaned out.
 

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Discussion Starter #13
That's crazy I would have never thought of that at all the only thing is the gaskets I'm pretty shore that's where I'm leaking gas at or so I think. I might just try that I just can't wait to get this done and be able to ride again.
 

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Discussion Starter #14
another thing I wana do as I got it apart is get some spray paint and clear coat and give it a paint job since it's falling over a couple times (not laid down riding just falling over) and now it has scratches everywhere. I want to just get it nice looking again and anything is better then scratches all over. I don't have the money to get a paint job the right way. Any ideas on this or would ya'll leave it scratched up?
 

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sounds to me like you have bad carb floats. they dont seal good anymore, so they start overfilling the carb bowls and you get all the symptoms you described.


-remove carbs, disassemble (removing all rubber pieces)
-soak carb bodies in carb cleaner overnight (you can get a bucket at any auto store for about $20...they look like a paint bucket)
-soak all the metal stuff in the carb cleaner too..jets, needles, etc. just nothing rubber. there will be a basket to hold all the small stuff.

-after overnight soak, blow some compressed air through the jets...If you dont have any you can get the computer cleaner and shoot that through. not necessary, but it helps if you have a dirty gas tank
-use that rebuild kit you bought. it will have new float needles.
-as you put everything back together, you may want to measure the float level (fuel height in carb bowl). Again, may not be necessary, but its better than taking em off again.

-put it back together a fire it up.

If you havent done it before, this seems more difficult than it really is. Just need to be careful to remember where everything foes that you take apart.



You can do an inner gas tank resurfacing too if its rusty in there. Por-15 is the best from what I hear. Just make sure you follow the directions and do NOT skimp on the drying time. In fact, you should double the last step before putting gas into the tank. 2 days drying minimum. I know its hard to leave it alone, but its worth it.


Painting is easy too. Not too sure how involved you want to get, but if you arent doing body work, just painting that is really easy. Just make sure you give it a VERY good cleaning before you paint, and sand down the old paint with 400-grit sandpaper before you clean. Sand, clean, primer, paint(color), paint (clear). And make sure you buy the Duplicolor paint that uses the fan blade. Its so much easier to paint and its easier on your finger, trust me.
 

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Discussion Starter #17
that one idk i went to the dealer and got them to order a rebuild kit I will know more on monday
 

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Definately need all orings replaced. I have never used the lemon juice trick b4, but have heard of it. I know if you go to like and auto parts store they sell solvent in a can that comes with a tray. all ya do is break down the carbs remove all jets and needles as well as their orings and soak only metal parts in it for 24 hrs each. after that use some fine wire to clean all passages.(some compressed air is good as well) then use a complete kit and replace all orings. After that find a manual and do the valves. you will need a new valve cover gasket for that. After the carbs are built making sure the float height is important. Then put it on Pri for a few seconds fire it up and switch back to run. she will run like a beast.
 

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where exactly is your carb leaking from? a hose? filter? or float bowl?

Also has there been any mods to the bike? Ie exhaust, individual filters?

Also check your floats they may be worn. when you have the floats outa the carb, put em in a container big enough to hold them and some fuel to make em float, let them soak over night (or 2) to see if they are still floating. If not replace em.
 

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Discussion Starter #20
sounds to me like you have bad carb floats. they dont seal good anymore, so they start overfilling the carb bowls and you get all the symptoms you described.


-remove carbs, disassemble (removing all rubber pieces)
-soak carb bodies in carb cleaner overnight (you can get a bucket at any auto store for about $20...they look like a paint bucket)
-soak all the metal stuff in the carb cleaner too..jets, needles, etc. just nothing rubber. there will be a basket to hold all the small stuff.

-after overnight soak, blow some compressed air through the jets...If you dont have any you can get the computer cleaner and shoot that through. not necessary, but it helps if you have a dirty gas tank
-use that rebuild kit you bought. it will have new float needles.
-as you put everything back together, you may want to measure the float level (fuel height in carb bowl). Again, may not be necessary, but its better than taking em off again.

-put it back together a fire it up.

If you havent done it before, this seems more difficult than it really is. Just need to be careful to remember where everything foes that you take apart.



You can do an inner gas tank resurfacing too if its rusty in there. Por-15 is the best from what I hear. Just make sure you follow the directions and do NOT skimp on the drying time. In fact, you should double the last step before putting gas into the tank. 2 days drying minimum. I know its hard to leave it alone, but its worth it.


Painting is easy too. Not too sure how involved you want to get, but if you arent doing body work, just painting that is really easy. Just make sure you give it a VERY good cleaning before you paint, and sand down the old paint with 400-grit sandpaper before you clean. Sand, clean, primer, paint(color), paint (clear). And make sure you buy the Duplicolor paint that uses the fan blade. Its so much easier to paint and its easier on your finger, trust me.
Thanks man I will keep it in mind and paint it like you said. I want it to look nice and on top of that I'm ready to have a more custom look. Well just got a call while righting this and my carb kit is in so now it's time to go pick it up and get a weekend job now.
 
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