fuel coming out exhaust

hello i have a 1980 kz440 and there is fuel coming out the exhaust when it runs does anyone know what is causing this? thanks!!!

DO NOT START THE BIKE!

The most common cause of raw fuel spewing out the exhaust pipes is a combination of a failed vacuum petcock and a failed needle and seat combo. The flooded cylinder should be easy to spot by taking a quick look at the spark plugs.
The petcock is pretty easy to test. Get an empty jar or can and a few rags. Pull the fuel line off the petcock while holding the container under the petcock. If fuel runs out with the engine off, the petcock needs to be rebuilt.

Next, the offending carb needs to be addressed. It will be the one connected to the cylinder with the nasty plug mentioned above. The needle and seat may just need cleaning, but replacement may be the ultimate solution.

At any rate, DO NOT START THE BIKE! If fuel is leaking enough to see it out the pipe, then there is a good chance that there is a bunch in the crankcase. Starting a bike in that condition can lead to catastrophic results. Think large, two-wheeled grenade. Remove the oil filler cap and take a sniff. If it smells like gasoline, then a complete oil change is mandatory before starting the engine.

This can cause fire/explosion/panic or even a hydro lock condition resulting in bent/broken connecting rod(s).

Raw gas, or puffing vapor?

If raw gas, listen to TexasKZ, DONT RUN IT.

Time to spend some $$$ and rebuild the carbs/petcock.

GL!

clutch85 wrote:

hello i have a 1980 kz440 and there is fuel coming out the exhaust when it runs does anyone know what is causing this? thanks!!!

Single or dual muffler(s) on this 2 cylinder model?

Is it running on just one cylinder? Which one?

Non-combustion issue may relate to carb, ignition, spark quality, or valve clearance.

Might be simply pushing out non-combusted fuel mixture of normally ingested amount.

For heavier fuel emissions, would suspect faulty float valve function in carb.

Good Fortune!

awesome guys thanks!! i was worried my engine was no good i will buy some rebuild kits and rebuild the carbs it is liquid fuel coming out, it is running on both cylinders and is a two into one exhaust, i just adjusted the valves and pretty well have all new electical like new coils, plugs, leads, points so it has proper spark so surely it is the float needles from what i hear so far

Would add change oil and filter to the list.

Be sure to fit a good in-line fuel filter to keep the freshly cleaned carb internals in pristine condition.

Click here > In-Line Fuel Filter from Z1E

Good Fortune!

Was this issue ever solved? I'm having the same problem. Raw fuel is dumping out of the exhaust drain. I've cleaned the carbs 3 times trying to get this right, as well as installed new needles. I've seen some people polish the fuel needle seat but I can't figure out how to get these ones out and i've already scratched the outside of one trying. My fuel petcock appears to be working correctly, and i've even tried capping the vacuum inlets and running straight on/off gas. Any help would be seriously appreciated.

Have you done the clear tube level check....... could be its set to high.

I've seen some people polish the fuel needle seat but I can't figure out how to get these ones out and i've already scratched the outside of one trying.

On some carbs e.g. Keihin CV34, the seat is pressed in and is not removable. I have found that a Q tip and Brasso works well followed by some carb cleaner

It might help if we knew what bike and carbs you have.

I have tested the float level unfortunately, if anything they seem a little low. They are both exactly the same as far as I can see, and the only side leaking is the left.

I apologize for not leaving that information. I've got an 80 kz440 A1 with the Keihin CV carbs . After posting the comment I did come to realize they were pressed in, and I used the q-tip trick to polish them pretty good but unfortunately it didn't make a difference. I also just did a pop test on them to make sure the float needles were seating correctly and they both appear to be normal. Not seeing any leaks around the needle seats either.