Any Advice would make my day. (Leaking Gas Badly)

-I've posted on 5 forums so far and no luck with any answers maybe one of you guys can crack the case.
Let me say first that I am 18 working two jobs/school to support my family until there able to work again. With that being said obviously time and money are tight, so if your answer is a full rebuild that wont really help me.

-(I'll try to keep this short but detailed)

-I got my 1980Kz650. It has a swapped motor from a 1988Kz 650 and is bored out (I believe .30 over but I haven't taken a look at it just took his word on it) I road it home fine which is a little over two hours. Battery was dying and when I made it home and let it sit for 2 days the battery killed over.

-Finally got a new battery and it fired right up. First start alot of smoke came out (Looked like a dang two stroke dirt bike) but it cleared itself up by the time it warmed up. Then it started leaking gas after it was warm and idling fine at 1K.. BADLY.. I am talking probably 5-10 cups full of gas in 4-5 seconds and then I jammed a large pan under it. The gas is coming from the black tubes connected to the carbs. It's not just flowing out by gravity.. It's pumping a big shot of it every 10 seconds or so with quite a bite of force. This leads me to believe the floats aren't causing this?

-I took the carbs off completely cleaned them out put them back on fired it back up and I believe it actually made the bike leak worse then it did before.

-When I turn the bike off after its been idling and shut the petcock off (I can't ride it because all the gas will poor out behind me) it will keep pumping gas out for about a minute or so until the carbs are empty.

-I am trying to think of more information that I could put but that is about it. Probably not that complex of a problem but like I said I've posted it quite a few time and no luck so far.

-Also: I thought my throttle cable was stuck open a little but my idle stays fine at whatever I set it to
And it only comes out of the two tubes (rarely the third) that are connected to the two carbs on the left side of the motorcycle.


Possibly a petcock problem? Tank problem?
Thanks for the help if you lasted reading through all that junk.
-Trev

First, welcome to the KZR Nation. You are in the right place for all things KZ. Great to have you here!

Fuel over-flow... this sounds like a typical and all too familiar fault symptom for a carbureted bike. I had a very similar symptom and countless other members here have also and they were solved... so that's good news.

The black tubes are the carburetor's Float Bowl Overflow Tubes, one for each carb and they seem to be doing their job just great by directing fuel away from the Engine and bike in general. Sounds like Float Bowls for carbs #1, #2 and sometimes #3 are filling up.

First, and cheapest try doing the Fuel Service Level Adjustment using the Clear Tube method. See diagram below:



If that does not eliminate the symptom, then move on. The Needle Valve assembly is responsible for opening and closing so as to control the flow of fuel into the Float Bowl. If debris and stuff from the Fuel Tank get past the Fuel Filter in your Petcock and lodge in between the Needle Valve and the Needle Valve seat... well as you can expect the fuel will flow uncontrollably, fill the Float Bowl and spill out via the black Over Flow tubes. Clean out the Needle Valve assembly, clean out the Petcock Fuel Filter Screen - if it's still there - rinse out the Fuel Tank with clean fuel and drain out the Petcock into a re-cycling container, and fresh and hopefully cleaner fuel, add a good quality clear in-line fuel filter (e.g. under $2.00 USD from Z1 Ent.) and try again.

If the fuel continues to overflow then it may be that the Needle Valve seat is deteriorated and needs to be changed out for a new one... not a used one from the x-bay. They could run you $15 - $20 USD per carb... sounds like you need 2 or 3 complete Needle Valve assemblies. When you get the replacement Needle Valve assemblies be careful and DO NOT mix up the parts from different assemblies as they may not seat properly.

If the fuel continues to overflow then it may be the Float that is stuck or gets hung up or there is a leak in the Float and it is partially flooded. Be prepared to swap out one or more of the Floats. Some of the members here may be able to hook you up with something used but still working.

Hope that helps.

Best of success,
Bill

FYI, This is a diagram for the Fuel Service Level Adjustment using the Clear Tube method - it comes directly out of a manual... you need a manual:



Don't worry about buying a brass tool/guage, just remove the brass Drain Plug from the Float Bowl and jam in a cheap plastic Vacuum hose adapter into the drain hole. Then attach a cheap clear plastic hose and you save $ 65.00 USD. Me, I like brass tools. :laugh:

Best of success,
Bill

PS
Please add your model, year and location to your signature to get the very best responses... and yes, it’s considered real friendly too.
Bill

I am not at all familiar with your set of carbs but is it possible that the drain screws are missing some o-rings?

Howdy. Drain some fuel into a container & inspect it for debris. It could be that crud is keeping the float needles from seating properly. If there is debris, drain the tank & carbs, & install an in-line motorcycle fuel filter. An automotive fuel filter may not flow enough fuel. You may need to rinse/clean the tank, and you may need to remove the carburetor float bowls & clean them as well.

The petcock: most of them have ON-RES-PRI. When the bike is off, fuel should not flow when it's set to ON or RES; when the bike is running, engine vacuum pulls open a diaphragm to allow fuel to flow by gravity. PRI bypasses the diaphragm to allow fuel to flow by gravity - engine running or engine off. Check the petcock to make sure it's functioning properly.

PS: what location or city?

Trevorreplys wrote:

Then it started leaking gas after it was warm and idling fine at 1K.. BADLY.. I am talking probably 5-10 cups full of gas in 4-5 seconds and then I jammed a large pan under it. The gas is coming from the black tubes connected to the carbs. It's not just flowing out by gravity.. It's pumping a big shot of it every 10 seconds

It has to be gravity unless somebody installed a fuel pump on your bike.

This problem is almost always caused by the floats/needles/seats in the carbs needing to be cleaned and or adjusted. The black tubes are overflow tubes.

You also need to drain and flush the tank, clean the petcock assembly and install inline fuel filters. Then clean the carbs and they will stay clean.

If needed.

Good Fortune!

+1 on checking the float height and verifying the condition of the needles and seats. If you still have fuel leaking after you know the floats aren't suspect there's really only one other thing it can be, and that's a cracked tube on the inside of the float bowl. I've run across that a couple times. I believe some have had success soldering the cracks on the brass tubes if you do find that to be the issue.

I'll add that you should make up a way to hold your carb's and feed some fuel to them while off of the bike, this will let you do the float level test and leak check before messing around hooking up those airbox boots. That way you can be sure of no leaks before reinstalling.