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Discussion Starter #1
I had to clean the carburetors ...... (4x 34mm Keihin CV). As I had the carbs off, I wanted to check/adjust the fuel level height. I “mounted” the carbs on a special made metalplate with the same angel as on the bike. The “gastank” was a 1 L lemonadebottle and the difference from gasolinelevel in the bottle and the bottom edge of the carburettorbody was about 45 cm (approx.. 10 cm more than a full gastank on the bike).
My problem is, that even though the float height is about 17 mm (as they should be) the fuel level height exceeds the recommended max at 1 mm above the carburettorbody many times. The height gets so high that the fuel runs out of the carbs (comes out of the Pilot Air Jet and/or Main Air Jet). Tried it a lot of times now and have even installed new fuel inlet valve needles to try to make up for the failure. I´ve also checked the mating surface of the float needle for corrosion, the upper carb vent lines etc. Nothing´s wrong here - I think.
I can´t figure out what the problem is/what I might do wrong???????????
 

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I want the top carb body line of where I push the float bowl under. Get it? I separate the bowl from body, that is my horizontal line.

I want to set my float level with the line. I don't measure with tool. I bend the tang so the flow stops and flows when I drop bowl within a mm or 2.

Again, I want a level line of the float to line up with the lower horizontal line of the carb body. I turn the gas container over so the fuel flows. I watch the flow stop the higher I raise the float.

Where did my float level land once I stopped flow? Lower than center? Higher than center? So I am more working the physical than relying on some bent up float you don't see [to to check the floats being level to each other] is higher than the other and you take that lower/higher measurement instead of a flowing static move you can physically see stop the flow.

Even your floats will have a gas line etched in it. Follow that old pattern.
 

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Discussion Starter #3
Hi
Thanks a lot for your reply, but I´m not sure I understand what you´re saying.
It seems you´re used to working with carbs though, so if you´ve got the time I can send you som Pictures of my line up and everything. Maybe you can se something I have to check up on............... I´m a kind of newbie in this forum - is it possible to send a PM, where we securely can pass on an e-mailadress?
The carbs are leveled in one direction at has the excact same angel as they have on the bike the other way.
I have tried to bent the floatpin, but it didn´t seem to affeckt the float height (mysteriously). it should have........
Its not my first time working with carbs and maybe thats why I´m so god damn frustrated, why the hell it´s so tricky (sorry for my language - I´m a bit edgy due to the lack of any solution to the problem ;-) )
The most logical explanation would be bad fuel inlet valve needles or the matching mates, but the needles are new (not original though - due to the horrific prices) and I can´t see any damage on the mating sufaces.

Heeeeelp!
 

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Try adjusting the floats so that they close the needle and seat a bit sooner. The floats could be a bit heavier with age and don't not have the buoyancy of new ones.

If you aren't riding full throttle all the time, you will most likely not notice a little less fuel in the bowls.
 

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Discussion Starter #5
I often rides full throttle :)
I don´t think the needles shall close earlier, but as I mentioned in my second reply, I have tried to bend the tang on the flloat on one of the carbs so it should close earlier/sooner, but it didn´t have any influence on the gasoline level what so ever - very strange ! AND ununderstandable..............
 

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Another way is to stand the carb body so the horizontal line is now vertical. So you now let the floats close the needle by the angle they create.

Now, you push the float to see if the tang is pushing the pin's spring [if it has one] in the needle? If there is a gap between the tang and needle? See it? If the tang is pushing the the pin's spring like it collapsed it fully? Get it?

So you are making that float as vertical as it was horizontal. But this time you are not having your finger pushing up on the horizontal position. You are looking at the floats statically level on their own in the vertical position.

This is more, 'sweat the details.' Walk away from it for a day and go back to it with a fresh look. This is somewhat simple is the float via mm measurement and/or hand-eye the puppies.
 

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This is cut/pasted from my post in another forum, although the carbs are 38mm EXUP mikuni's the procedure is the same.

You may find that if you have Ben the tang and it's not altering the fuel height, then the fuel is bypassing the needle, if you have new (correct) needles, then the needle housing must be worn, or the fuel is leaking past the "O" ring on the housing itself.

------------------------------------------//-----/-----------------------------------


This is the procedure to set the FLOAT HEIGHT to 14 mm.

This is not setting the procedure to set the FUEL HEIGHT (as mentioned in the manual) although it should be correct when the FLOAT HEIGHT is set to 14mm

You need to make a gauge like this out of cardboard or an old credit card, the part that sits over the floats needs to be 14mm



You need to fit your new seals/needles etc and then refit the bowl like this to ensure the float is held securely, the jet holder can be fited or not, it doesn't matter





You need to invert the carbs and have them sitting at an angle like this



so that the float is resting on the needle but not compressing it, like this



not like this



You can now use your gauge to set the height that the float sits above the gasket face of the carb, the highest float should just touch your gauge like this.

You have to bend the small "tang" that depresses the centre pin of the float needle to achieve this.



Reassemble the carbs and you're done
 

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Discussion Starter #8
thanks and especially Creedxup for the fine illustrative explanation. I´ve doen excactly like the manual says (at least I think ;-) ). Well lets give it a try..... The manual says:"To check the float height, hold the carb so the float hangs Down, then tilt it back until the valve needle is just seated (the rod in the end of the valve shouldn ´t be comppressed. Measure the distance from the carb body to the top of the float.
I´ve done this procedure.
 

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The way you're doing it looks fine, although to ensure the float is sitting securely on the needle, I would tilt the carbs over a bit so that the weight of the float is truly on the needle (without compressing the plunger/spring)

Are all the fuel heights too high? (are all the carbs flooding)

You may have a damaged (worn) needle seat or a bad needle.

If only 1 carb is flooding, try to swap the float and needle to another carb to test whether the fault is in the carb or on the float/needle.
 

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I´ve checket the carburettor once Again and with a bit better outcome ;-)
I still can´t visually (eyes) see anything wrong with the seats BUT as I continued my examination of the needle pin and seats I found that especially two of them had a tendency to leak.
At first I placed the carbs with the bottom up and bowls dismantled. Connected my vaccum/pressure"gun" (handdriven) to the gasinlet on the carbs and at first I used waterbased gasleakliquid. When I only used air they all leaked at under 5 psi (at so low pressure I can´t measure the pressure excact).
The NeXT try was based on the former mentioned external “gastank” (a 1 L lemonadebottle) with a difference from gasolinelevel in the bottle and the bottom edge of the carburettorbody at about 45 cm. Now "only" two of them were leaking.
Dismantled the gastank. Off with all the needlepins. A motorcyclemechanic told me that they apparently used the excact method I mentioned before. A small millingmachine. I haven´t got something like that so I carefully took some cotton buds and a little toothpaste on the tips and turned them back and forth several times in each seat.
Reassembled the carbs, put the needles and floats in and used the later method again. No leaks.
With gas in the carbs I connected my gun to the gashose and pumped. Did it several times. The were holding the pressure until app. 7,5 psi. Then two of them started to leak. At 9 – 10 PSI all leaked.
But thats much more pressure than the MC-gastank can put on the carbs, so I think its fine.
The mechanic I spoke to may apparently have other experinces than some of you. He advised me never to try to pull the seats up as I´d never get them gastight again.
Has any of you got any picture that show were the O-ring is situated on the CVK34? How do you get them separated from the carbs?

I did have a new experience though……. The angel of these carbs had a very big impact on the tightnes of the needles.
I assumed that the gaslevel mentioned in the manual (max at 1 mm above the carburettorbody) should be measured with the carbs on the MC OR!!! Dismantled BUT with the same tilt/angle as on the bike. IF I keep the carbs horizontal its very ease to keep the fuel height in accordance with the manual. In fact the gaslevel was a bit lower than in the manual.
Another thing I found out was, that even if the floats are at app. 17 mm above the body when they start to affect the needles (in accordance to the manual) there were a big difference between especially one of the floats height and the others. Thought this was very odd so I diamantled the one and one of the others. I also think there is a difference in the spring”tightnes” when I compressed them with a finger. Reassembled though. I have to check other things before I reassemble the bike, so I can´t give a repport on how successfully the mechanicing was ;-)
 

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I agree with creed. I'll take a guess: are the two leaking on the left side? This makes me assume there is no center stand so the bike sat on a left angle. The gas level is now at the two left carbs, but the angle made the right two carbs dry out.

But with the gas deteriorating, a chemical reaction can cause the green stuff to eat at the brass. The tip may be made out of rubber so this may have a ring around the cone part, and this too can cause dripping.

So my theory is that the gas etching sort of points to what creed was saying. You have to change the needle and seat as a set. So the theory goes, I keep bumping up on friction and that causes heat. So as much as it cools with gas over it all the time, it still wears as if you rub both hands together and now which one remained cold? Which did not wear: that you think you can get away with the etching you didn't change or vice verse with the old needle reused on a new seat?
 

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Discussion Starter #13
I´m thankfull for your replies!!
OK thats why we didn´t understand each other :) .... Mine is CVK 34 Kawasaki 1989 F3: Zx750 Carburetor Parts - schematic partsfiche and yours are different. Thats why I simplyy didn´t understand the thing about the O-ring. Mine hasn´t got any O-ring and can´t even be bought (as far as I know)
Allthough my bike is an old one the carbs were used on a lot of bikes and also newer bikes than mine. -And a lot of problems is still the same no matter which carb type we´re talking about.
I checket the ignitiing system and cooling system (electrical) yesterday and reassembled the carbs and put them on. Today I think I reassembles fairing etc and take a full throttle trip to see how good (or bad ;-) ) it Works.
Anyway thanks for your help.
btw I took a lot of Pictures during the procedures just like Creed. It´s much easyer to help others or seek help if you got Pictures on the damn Things *SSS*
 

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You need to inspect the needle valve assembly and seat under the biggest magnifier you can use...any corrosion anywhere is a failure waiting to happen. Then check the floats to make sure that they actually "float" as opposed to sinking.

I just finished repairing a set of those exact carbs for an '87 750 ninja. Forget about doing anything on the bike...doesn't work that way. You can check the float level on the bike by running a hose connected to the drain of each bowl to verify correct height. (in the manual) If you have any issues with these, I can probably help if you wanna pm me, and always ...NO questionable parts, and CLEAN as possible are the best starting points. without those, you're just gonna get really good at R&R of the carbs

FYI, if fuel is spilling out of the carbs, your needle valve is either wasted or you've got some shit in there. Float height won't get you there
 

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Discussion Starter #15
Joker. I´m not impertinent, and I would really like to continue talking to you, but it would be really nice if you would read what I have mentioned in the above :)

IF it was possible I´d placed under one of my microscopes, but the way the seat is situated it´s not possible........

Do you have any comments on the leakpressure I mentioned?

I´ve reassembled the bike. And..... another god damn problem. Overheating!!!!!!

Checket the Whole system. Fan, fan "switch", temperature measurer, thermostat. Everything seems OK in accordance with the manual. -Or almost everything.

The new problem. The MC runs fine and if kept on centerstand/Idle it heats up at the fan starts (maybe a Little late, but it starts). The mc kan be ridden 15 km at 60 - 110 km/h BUT if I give a 3/4 - full throttle it heat up so much that the Water start boiling BUT the fan doesn ´t start and it´s very hard to get Down in temperature. I think it indicates a thermostat problem OR defective waterpump - though I´ve never heard of a defective pump........
I really can´t figure out why the manual says that the thermostat should lie between 69,5 and 73,5 degrees celcius. On both this particular MC and on another I´ve checket (I have 5 GPX´s) the thermostat is stamped 82 degrees and I´ve checked both in heated Water. Both opens at approx. 85 degr. and is fully open at 90 degr.
 

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I´ve checket the carburettor once Again and with a bit better outcome ;-)
I still can´t visually (eyes) see anything wrong with the seats BUT as I continued my examination of the needle pin and seats I found that especially two of them had a tendency to leak.
At first I placed the carbs with the bottom up and bowls dismantled. Connected my vaccum/pressure"gun" (handdriven) to the gasinlet on the carbs and at first I used waterbased gasleakliquid. When I only used air they all leaked at under 5 psi (at so low pressure I can´t measure the pressure excact).
The NeXT try was based on the former mentioned external “gastank” (a 1 L lemonadebottle) with a difference from gasolinelevel in the bottle and the bottom edge of the carburettorbody at about 45 cm. Now "only" two of them were leaking.
Dismantled the gastank. Off with all the needlepins. A motorcyclemechanic told me that they apparently used the excact method I mentioned before. A small millingmachine. I haven´t got something like that so I carefully took some cotton buds and a little toothpaste on the tips and turned them back and forth several times in each seat.
Reassembled the carbs, put the needles and floats in and used the later method again. No leaks.
With gas in the carbs I connected my gun to the gashose and pumped. Did it several times. The were holding the pressure until app. 7,5 psi. Then two of them started to leak. At 9 – 10 PSI all leaked.
But thats much more pressure than the MC-gastank can put on the carbs, so I think its fine.
The mechanic I spoke to may apparently have other experinces than some of you. He advised me never to try to pull the seats up as I´d never get them gastight again.
Has any of you got any picture that show were the O-ring is situated on the CVK34? How do you get them separated from the carbs?

I did have a new experience though……. The angel of these carbs had a very big impact on the tightnes of the needles.
I assumed that the gaslevel mentioned in the manual (max at 1 mm above the carburettorbody) should be measured with the carbs on the MC OR!!! Dismantled BUT with the same tilt/angle as on the bike. IF I keep the carbs horizontal its very ease to keep the fuel height in accordance with the manual. In fact the gaslevel was a bit lower than in the manual.
Another thing I found out was, that even if the floats are at app. 17 mm above the body when they start to affect the needles (in accordance to the manual) there were a big difference between especially one of the floats height and the others. Thought this was very odd so I diamantled the one and one of the others. I also think there is a difference in the spring”tightnes” when I compressed them with a finger. Reassembled though. I have to check other things before I reassemble the bike, so I can´t give a repport on how successfully the mechanicing was ;-)
Although i am three years late, but i am having the same problem, i need help to find some things to set up my float height and float timing.

1. What should be the angle at which the carburetors are to be placed at.

The service manual should have the float height along with the "angle" at which the carburetors are to be placed on the bench, this angle represent the seating position of the carburetors when they are installed on the bike.

As per my past experience if you place the carbs (on the bench) at the specified angle and set the measurement of the floats to the specified values, the float timing shall be perfect.

Would be great if you could help me in this
 
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