KZ250 C 81' Single, fuel pours out carb overflow after rebuild

I've finally got my rebuilt cv32 carb fitted to my 81' single KZ250 C (the bike came with the wrong carb on it originally). It's had new o-rings and all jets etc removed and cleaned then blown out and re-fitted.

I tried starting it up today and it turns over but won't start.

Fuel just drips out the overflow outlet on the bottom of the float bowl when the fuel tap is turned on and I try to start the bike.

I know it's not dirt in the carb and I know the floats are moving ok. I'm guessing it may be the float height that needs setting correctly on the float pin tang (would this cause the problem I have?). But I have no idea what this should be set to, or how to measure it.

Also, the pin dangles from the floats via a little bit of square metal wire. The metal wire has 2 tiny springy bits on each side. I'm not sure which way these should face when fitted so I could have put that part back on wrong.

Sorry If I haven't described this very well.

I'm using a pod filter with standard jetting (for now).

Post edited by: uniquezfreak, at: 2008/02/02 14:32

Petcock or floats, one or the other.. Not sure about the wire your talking about.. Kawasaki.com and try a parts diagram or your manual?

If you had your carburetor rebuilt by someone, take it back to them and let them make it right. While you may think you have no issues with stuff in the carburetor, it is very likely you do... stuff left over from the rebuild if any serious cleaning was done. You may also have an inapporopriate fuel level or the float needle is installed incorrectly on the tang on the float. Last, you may have the vent plugged which will also cause the carb to spew gas.

The diagram below is the '81 KZ250 oem carb per Kawasaki.com, but uncertain if it's the same, since yours came with the wrong carb on it originally.

In most cases, fuel driping out the overflow outlet on the bottom of the float bowl is because the float needle/seat interface is failing to completely seal --this being due to wear or crud, more often crud.

As to float height, I would use the quick easy clear plastic tube test to assure the fuel level is about 2-4mm below top of the float bowl (for a typical carb).

The float itself might possibly be leaking (and therefore not "floating" too well), but this is a rare case as compared to the usual crud case.

Try this first -- while first attempting to crank, tap smartly against outside of the float bowl with a plastic mallet, which often allows the float needle to re-seal in its seat, whereupon the overflow leak magically stops.

You said, I know the floats are moving ok. Floats? -- plural? -- will presume this is a typo as there is only one float involved in a single carb.

When it turns over but won't start, does this mean the engine completely fails to fire (as if the spark plug was not connected)?

The metal wire with 2 tiny springy bits on each side is probably the cir-clip shown in the daigram. Study it carefully, along with diagram, and hopefully be able to figure out the mechanics involved so as to assure correct reassembly.

And please forgive the guesswork here as I'm uncertain as to exactly which carb is in question.

Good Luck!

Patton, thanks very much. It is the same carb as on the diagram. I replaced the wrong carb with the right carb, thanks to others on here who helped me identify what I needed to source second hand.

There is only one float, my error, I referred to it in the plural due to my interpretation of the one floaty plastic thing on either side of the carb. - Joined in the middle by a thin metal strip that holds the float pin. - Which you suggested may not be sealing.

Your bang on! - it's exactly like the spark plugs is missing or the engine is not firing. - Except I've checked the plug has a spark.

The diagram is very useful. I can already see that I have part small wire spring clip that the float pin dangles from installed back to front.

I'll have another go and see what happens.

Also, check the overflow tube itself for a hairline crack. A friend had just that problem last summer with that type carb on an old honda. After taking the bowl off several times checking the seat and needle and that the float wasn't catching on anything,, we finally found a lengthwise crack in the tube.
To repair it, we used a plastic stir straw that one of the local coffe shops has on the counter. It had to be heated with a hair dryer to get it down over the tube. Then we mixed up a bit of JBWeld and put a small pool of it in the bottom of the bowl to seal that end of the tube so gas couldn't seep between the two tubes. Worked like a charm.

Post edited by: The Milkman, at: 2008/02/03 08:17

Post edited by: The Milkman, at: 2008/02/03 08:49

I had to go take a bowl off a set of 305 carbs to get my mind straight as to how that little clip installs. I'm going to try and explain it as best I can. On the needle at the end that does not fit into the seat there is a slot that the open end of the clip snaps into, do this first. The other end of the clip should be closed together. When you go to re-install everything hang the needle on the float tang from the clip and fit the needle into the seat then put the hinge pin for the float back in place. Before you put the bowl back on turn the carb rightside up and check that the float moves up and down freely with no binding.

I hope this is clear if not let me know and I'll try to better explain it. Also since you have it apart, I've had good luck cleaning up the seat with a Q-tip dipped in a little Mothers mag polish. Just spin it around and the brass seat will polish up very nicely.

Milkman's post about checking the overflow tube itself for a hairline crack reminded me that we don't yet know whether any fuel mixture is reaching the cylinder combustion chamber. In other words, is it flooding out or staying dry? Either condition would prevent combustion from occurring as it's supposed to inside the chamber.

Flooding from whatever reason would leave fuel residue on the sparkplug detectable by sight and smell. Whereas absence of any fuel mixture would leave a new spark plug still looking clean and dry.

Hairline crack in overflow tube could allow fuel entering the floatbowl to escape through the overflow instead of attaining he correct operating level. This could be one reason for a dry sparkplug.

On the other hand, a flooded (wet) sparkplug might be caused by failure of the float needle to seat/seal as it's supposed to do when pushed by buoyancy action of the float (which might result from crud).

If we could we get a report on whether the sparkplug is flooding or just staying dry, it may help the diagnosis.

Post edited by: Patton, at: 2008/02/03 09:04

Ok, I've stopped the fuel leak I didn't have a cue tip, so I put a cotton ear bud (soaked in cleaner) in a drill to ensure the float needle seat was clean.

I ordered a new float needle (those little things are not cheap!), as the old one looked worn. I also adjusted the float height to match another second hand carb that arrived in the post for spares.

(The other second hand carb is dirty as hell, but I figured the float height may have been right, so copied it on my current clean carb).

The only problem I have now, is that the bike still won't start. It turns over ok, but doesn't fire.

I've checked that the carb is getting fuel in the float bowl by undoing the drain screw. (incase I'd adjusted the float height to much in the opposite direction).

I removed the spark plug and it was black as night. So I got a hand held blow torch and tried to burn the oil off it.

I refitted the spark plug and held it on the cylinder head casing. It sparked, but was kinda on and off. a few weak sparks then the odd strong one. Some times it was hard to tell if it was sparking at all.

I'm ordering a new spark plug tomorrow just to be sure.

I'm not sure if it was dry because it took me so long to unscrew the spark plug (about 1 minute) or because something else is stopping fuel getting to the engine.

If fuel is in the float bowl I can only guess that the primary or secondary jets may be blocked? - But I'm pretty sure I blasted these out with a straw and cleaner when I rebuilt the carb.

Post edited by: uniquezfreak, at: 2008/02/07 16:01