78 KZ650 Project needs serious TLC

Some later versions of Firefox were having issues recently with regard to posting images on the forum.
Don't know whether this has yet been resolved.
Meanwhile, I have continued using the older version, which seems to still work just fine.

As to fuel discharge from the overflow, if not already done, would assure that the float wasn't inadvertently installed upside down, as is possible with some carbs.

Good Fortune!

Patton,

Thanks! Fixed the picture issue. Carburetor on the other hand is a negative. I have made sure the float is installed right side up. I am really not sure whats going on. I may be to the point of taking it to a professional. But im trying to keep cost down.

If not already done --
While idling, and overflowing, could rap smartly and repeatedly against the carb float bowl with a plastic mallet or large screw driver handle. Which sometimes resolves the issue.

With carbs again removed (groan) and back on the work bench, could swap the leaking float valve -- both needle and seat -- with the non-leaking float valve -- both needle and seat -- from another carb. Don't swap the floats.

While still on the bench, introduce gasoline [or mineral spirits or common household rubbing alcohol] into the carbs to determine whether the overflow follows the float valve.

If leak persists through a supposedly closed float valve, it may help to chuck a q-tip in a drill for cleaning the orifice inside the seat.

Presumably, the float needle tip is in new condition.

Would assure the float valve and float are functioning properly while still on the bench and before reinstalling the carbs onto the engine.

Good Fortune!

It's also important to NOT mix-and-match float needles and seats when reassembling the carbs.

In other words, should always keeps the same float needle with its same seat.

Good Fortune!

Rory Byrd wrote: ...I've adjusted and readjusted the float....

If referring to a physical measurement of float height while the carb is upside down on the workbench -- that's an unreliable means for achieving correct fuel level.

Such upside down float height measurement dimension is sometimes mentioned in an FSM, and may have produced a fairly decent fuel level when the carb internals were relatively new.

Actually, "float height" is relevant ONLY to the extent it produces the correct fuel level , because fuel level -- not float height -- is the critical factor in a properly set up carb.

The "clear tube test" is the reliable method to measure the true fuel level, and assure fuel level being within specs.

Good Fortune!

Well, over the weekend she finally hit the road! Rode her about 30 miles total. Still constantly leaking out of the first carb overflow. Even after a soak, rebuild and then replacing the float. Next I think I will try replacing the bowl and if that fails, may need to get a new carb? I sure hope not.

She ran decent. Got her up to 65mph. I did notice after about 10 minutes on the road she had some trouble when I would jam on the throttle to accelerate. There seemed to be a delay between me hitting the throttle and the power getting to the back wheel. Im not sure if this is an issue with the clutch slipping or has something to do with my carbs.

Also, when I arrived back at the house, there was heaps of oil all over the back end of the bike. So I would say i have a pretty good oil leak coming from somewhere. Any Ideas of the best place to start looking??

It was good to get out on the road. Maybe a bit premature, but after 8+ months of tweaking and working, I had to ride it!




EDIT: Oh and my TACH came disconnected at some point also...looking into an all new set of gauges. Not sure if I will go back with the factory version, or something aftermarket.

I'm assuming you stuck to your guns and put pods on it? If so, the oil you see may not be from a leak; it may be coming out of the breather (that normally has a little hose going to the airbox) if you didn't put a little filter on it. Also, this problem can be worse if you over filled the oil.

The throttle hesitation you are experiencing can be caused by pods unless you got the carb rejetting exactly right.

As far as the carb overflow...

Fuel coming out of the overflow hose (the little hose on the bottom of the carb) is the common symptom of the 3 possible problems described below. Remember – NO SMOKING or other activities that could ignite the fuel while working on carbs!

1. The float valve is not sealing. This may be (and probably is) just a matter of some minor dirt in the float valve and is very simple to remedy and can be done with the carbs still on the bike. Turn off fuel; drain carb by loosening big brass screw near bottom; and remove the 4 little screws on the bottom of the carb bowl. This will enable you to remove the carb bowl. You will then see the float. If you carefully remove the float you will see a stubby little needle that mates with a brass orifice; together, these two pieces are the float valve. Assuming there is no obvious damage to the needle or seat, use a Q-tip and some carb cleaner to clean the seat of the orifice and the needle. Be careful not to bend the tang that is attached to the float. This tang is the piece that the bottom of the float valve needle rests upon, and it determines the fuel level in the bowl, so bending it will change the fuel level. With the float valve cleaned it should no longer leak. To prevent a reoccurrence a quality inline fuel filter should be installed between the fuel tank and carbs. If there was damage the needle and seat should be replaced as a set; they are available.

2. The brass overflow tube inside the carb bowl is damaged. When you remove the carb bowl you will see a brass tube attached inside and rising toward the top of the bowl. This is the overflow tube and it leads directly to the overflow nipple on the bottom of the carb. Normally, the fuel level within the bowl rises somewhat close to the top of this tube. If the tube becomes cracked or separates from the bottom of the carb bowl fuel will flow through it and out through the overflow hose. Checking the condition of the tube is very easy after you have removed the carb bowl from the carb. Simply hold the bowl level and fill it up near the top of the tube with water of alcohol and see if it leaks. If it does the best remedy is to replace it although some folks have found creative ways to repair them.

3. The fuel level is set too high. This condition occurs when someone has bent the float tang as mentioned above. This condition can be checked using what is referred to as the “clear tube test.” The test involves attaching one end of a clear piece of flexible tubing to the carb drain hole and holding the other end of the tube above the bowl/carb joint. When the fuel is turned on it should rise in the tube to a level 2.5 – 4.5 mm below the bowl/carb joint. If the fuel rises higher than that level it may run into the cylinders or over the upper end of the brass overflow inside the carb bowl (mentioned above) in which case it will run out the overflow hose. This condition is corrected by removing the float and gently bending the tang to raise the float valve needle position. Doing this may take several tries before achieving the desired fuel level.

Correcting each of these three conditions involves removing the carb bowl. This task can be made easier if a short screwdriver bit is used, and depending on which carb you are fixing a mirror may help you locate the screws on the bottom of the carb bowl. Also, it is not a bad idea to have a new carb bowl gasket available in case the old gasket is damaged while removing the carb bowl. Ed

After you have cleaned the seat you might consider polishing it as well by putting some rubbing compund on a q tip and spinning it around in the seat. Just don't use too much compound you could create a restriction.

So I removed the float bowl and filled it with mineral spirits while sitting level on my workbench and it started leaking when the level was below where it should overflow. I am thinking the brass may have a crack in it and that is where the leak is. Nevertheless, I am now trying to find a replacement float bowl. Does anyone have any idea where I can get a single bowl? I have seen on ebay a full rack of carbs for sale, but not an individual bowl.

Ideas?

Rory Byrd wrote: So I removed the float bowl and filled it with mineral spirits while sitting level on my workbench and it started leaking when the level was below where it should overflow. I am thinking the brass may have a crack in it and that is where the leak is. Nevertheless, I am now trying to find a replacement float bowl. Does anyone have any idea where I can get a single bowl? I have seen on ebay a full rack of carbs for sale, but not an individual bowl.
Ideas?

There are several methods whereby a crack in the overflow tube may be repaired.

Must locate the crack. It's usually easy to see. Or perhaps blow smoke through the overflow nipple while blocking the top entrance hole, to see where the smoke exits.

Where the tube is broken loose at the bottom where it connects -- that's a more difficult repair.

Good Fortune!

Patton,

If I locate the crack, what is the best method of repair? Say for example it is at the mid way point up the brass shaft? Would soldering be the best option? What would you recommend?

Solder

JBWeld

A slightly larger brass tube (from hobby shop) placed over the cracked tube, and soldered in position.

A section of thin rubber or plastic tube fitted snugly onto the cracked tube.

Heat-shrink tubing

Not necessarily in that order.

Good Fortune!