Puch won't stop leaking gas

Liz Nayadley /

Hello everyone-

I am hoping that someone out there can help with my problem. The first fuel leak was at the petcock so I replaced that with a new one. I ordered it from moped junk yard. The stem with the filter on it that goes into the tank seemed to be a bit long but, I decided to make it work. The petcock does not turn all the way off it continues to drip.

The second leak seemed to be coming from the bottom of the bowl on the bing carb. I took it apart and cleaned the bowl and replaced the gasket. I also used a permatex sealant just in case. The float and needle seem to be working. After I did all this the moped seemed to lose a bit of power. I also replaced the fuel line and fuel filter. Is it possible that because the petcock does not turn off all the way that it is causing the carb to overflow? or would that be a problem with the carb? any other suggestions that I can try? maybe testing the float somehow?

thanks for your help.



Re: Puch won't stop leaking gas

See Ya Moped Army /

I would never use Permatex to seal a carb float bowl. The gasket was all that was needed. All it takes is a tiny piece of sealant to block the seat and jet passages. Get that crap off the bowl.

Secondly, your float may have a hole in it or be set too high, thus the fuel is spilling out of the intake. take that float off and put it in a cup of water. If it sinks, it has a hole in it. If it doesn't, chances are your float is set too high. You will need to bend the tab so that the float causes the needle to seat sooner than it does now when fule enters the bowl.

Re: Puch won't stop leaking gas

Liz Nayadley /

Thanks for the tips...I am in the middle of doing your suggestions. The float does float in a cup of water. Yeah, the permatex was dumb (a suggestion from a nosy neighbor). I cleaned the bowl all up. I made a new gasket myself from that stuff at the auto parts store. Any chance it will hold up? I should probably test the float to make sure it is not leaking before putting all back on the moped? It's weird because I have taken this carb off so many times and it appears to stop leaking at first and then when it sits over night it starts leaking again. You don't think the drippy petcock has anything to do with it?

thanks lots


Re: Puch won't stop leaking gas

See Ya Moped Army /

You should use the stock fiber ring gasket. Ike of Ike's Bikes has them cheap. Buy spares from him if you do order them. Homemade gaskets for something like that are not always a good idea. An paper intake gasket is one thing, a carb bowl gasket is another.

A leaky petcock (sounds obscene) isn't the best thing to have because it is a potential fire hazard if the fuel line or carb leaks, like it does in your case. However, if the float is properly set, the fuel lines are nice and tight and flexible, all connections are tight, and the rest of the carb dosn't leak, it should not leak if the float is working properly. Having said that, I would still replace the petcock with a new one as soon as possible.

Good Luck!


Re: Puch won't stop leaking gas

Liz Nayadley /

I am trying to get the moped to start but, something weird is happening...

the fuel is not flowing to the carb from the petcock. when I take the fuel line off the carb and test the petcock it works fine...any suggestions?

Re: Puch won't stop leaking gas

See Ya Moped Army /

Try loosening the gas cap and see if the gas flows. There's an air vent in the cap that may be clogged up. How are you testing the carb for fuel flow? If the bowl is full of gas, fuel will not flow to the carb because the float needle will be fully seated.

Re: Puch won't stop leaking gas

Liz Nayadley /

I am trying to start the moped and it is acting like it is out of gas. The tank is full. When I turn the petcock on when it is hooked up to the carb. fuel does not flow. When I take the fuel line off the carb the fuel flows. I think the carb is empty and that is why it won't start. Maybe when I was cleaning the bowl in the carb I clogged up the intake valve? Maybe I moved the float tab too much and it thinks it's full? Does the moped need to be on to see if the gas will flow while the gas cap is off? I did it without it running and nothing is flowing...

Re: Puch won't stop leaking gas

Gregory Mcintire /

With the carb off the bike, and the bowl unscrewed from the carb, hold the carb exactly upside down. The float should be level with the world. I suspect your adjustment of the float has changed it such that when you put the bowl on the carb it is pushing the float up causing it to completely shut off fuel flow.

Another note: If your float valve needle has a conical metal tip and not a rubber coated tip then your carb will very likely seep a small amount of fuel when the motor is not running and assuming that your petcock does not shut off completely as you have said. It is normal and unavoidable for that type of float needle to seep very slowly. This will not hurt performance and will not overflow from the carb when you stop the motor assuming you turn the petcock OFF and it indeed shuts fuel off. If your carb leakage problem is a small puddle dripped onto the ground overnite then it is not a big deal. Just get a good petcock. If your carb starts dripping as soon as you shut the motor off, then something is wrong with the float or needle and seat. Even if you don't have a float bowl gasket at all, the carb should not leak if the bike is sitting still and on a level surface because the gasoline should never rise to the level of the gasket. But you need a good gasket anyway since the bike is not always sitting still! I only mention this to help you diagnose your problem.

Re: Puch won't stop leaking gas

Liz Nayadley /

The carb. is still leaking after all the adjustments I have made to the float tab especially when I turn the engine off. I just let it set on level ground and it continues to leak. The float valve needle has a rubber coated tip. What do I try next? Do I need a new carb. and a new petcock?

thanks for your help...


Re: Puch won't stop leaking gas

Get new float valve needle and clean seat really good (use toothpick and toothpaste to clean it if there is a deposit )

Make sure the screw on the back ( where fuel line attaches)have good gaskets and it's tight, most likely it is loose.

I would check this screw first.


Re: Puch won't stop leaking gas

Scott Brockerville /

I have the same problem with a puch (bombardier) moped with the bing carb. I have bent the tab on the float up and down so many times to try and stop the leak but it wont stop unless i bend it enough that the bowl pushes the float and needle up into the seat, then nothing flows. The float seems to be a styrofoam type and i was wondering if its possiable for it not to float enough to push the needle into its seat hard enough? We both have the same problem, somebody give us a cure.

Re: Puch won't stop leaking gas

That tip is not rubber.. it's Viton, similar to teflon..

try this..

Turn off the petcock.

Remove the carb. Remove the bowl. (Find a little plastic tub to catch the fuel)

(Attach the fuel line to the carb and tank and) hole the carb upright and turn the petcock on. Fuel will flow out.

Push up gently on the float itself. See if the fuel flow into the (missing) bowl stops.

Now you _know_ whether or not that needle is leaking. If it stops leaking you might still have a float level that is set too high..

You might also notice that the fuel is leaking form somewhere else and not into the bowl..

Re: Puch won't stop leaking gas

I am going to order a new float bowl gasket and both gaskets that go around the banjo on the carb. I am going to try to clean up the gas cap in hopes that the pressure is keeping the float needle from seating correctly. I don't want to get a new carb just yet but, all the gas is leaking into a pan slowly as I type...

Re: Puch won't stop leaking gas

if fuel is leaking past a broken bowl gasket, you could see it if you look closely.

If the needle is not seating, the bowl can overfill but the leak will not come from the gasket. Instead, the leak will be coming from the vent hole near the top of the carburetor. (all thses carbs have a vent hole to equalize pressure.. otherwise the carb will not function.. this hole is also the overflow outlet.)

If the fuel is leaking at the banjo fitting, that can also be easily determined by just carefully looking at it.

Before you go buying parts or suspecting rare problems (like a pressurized tank/clogged cap vent) find out exactly _where the fuel is leaking from_ . This information is vital towards curing the problem.

Re: Puch won't stop leaking gas

_ If the needle is not seating, the bowl can overfill but the leak will not come from the gasket. Instead, the leak will be coming from the vent hole near the top of the carburetor._

Actually, i misspoke. If your bowl gasket is broken AND the needle is leaking, fuel will seep out of the bowl gasket. However, a new gasket is only part of the cure. The other part would be fixing the needle leak problem.

And the carb might leak from other places besides the vent hole.. fuel might come from the needle-jet (This jet has nothing to do with the float needle..

In anycase, find out precisely where the carb is leaking from. If it's impossible to see while the carb is mounted on the engine, remove it and reattach the fuel line.. Hold the carb level, turn on the petcock and watch closely..

Re: Puch won't stop leaking gas

I have noticed fuel coming from a little black tipped button thing. I think this thing is to pump fuel into the tank? But the fuel leaks from all around the bowl. I just assumed it was leaking from the gasket (which does have cracks in it I've seen them). Is it possible that the fuel comes out of the vent hole that it can spread out and just run down the sides of the bowl. Whenever I would check for the leak it always seemed to start leaking first at the float bowl gasket under the banjo. I figured I would go ahead and get those gaskets since they are relatively cheap.

Re: Puch won't stop leaking gas

someone advised against using a gasket sealant on the bowl gasket and I agree.

But, strictly for the purpose of nailing down the source of the leak, i would try sealing that bowl and the banjo with sealant and reassembling it. Now you can get a better view of the source of the leak. Remove the sealant once the problem is cured.

That bowl will not leak at the gasket if the float level is correct, even if the gasket is missing. The level of fuel in the bowl should be lower than the edge of the gasket. (Someone correct me on this if im mistaken.. im going by my experience with other carburetors i know of)

So, i still think the needle is the basic problem. Why the needle is not seating properly and when it should is still unknown. I posted a way to test it earlier. You might try that test.

Re: Puch won't stop leaking gas

I just took off the fuel line that hooks up to the carb. The petcock does not turn all the way off ever it is constantly dripping. Could this have anything to do with my leak. Say the float needle does seat correctly and keeps gas from going into the carb. Where does that extra gas that sneaks out of the petcock go? It's got nowhere to go but, maybe out the fuel line near the banjo? just a thought...I am going to do that float needle valve test shortly...waiting for it to cool off a bit

Re: Puch won't stop leaking gas

Scott Brockerville /

I tried pushing up my float by hand, and it stops the fuel flow everytime. Put the bowl back on and it leaks everytime. The only way it doesnt leak wth the bowl on is when i bend the float tab that much that the fuel will never flow. Could the float not have enough bouancy to properly close the needle into the seat? Or is it the needle and seat, though they look fine. The way the bike runs now, if I keep it opened out and going fast, it runs fine. When i slow down, it floods itself with gas from getting to much.

So next question.....where is a good place in Canada to order new parts?

Re: Puch won't stop leaking gas

Yes. If the petcock leaks and the banjo leaks you are gonna be leaking forever. Fix them both.

For now, just use some gasket sealant on the banjo mating surfaces and that may cure the leak (temporarily)

That thing should never leak even when the petcock is wide open.

Repairing or replacing the petcock in on the list of things to do later.. You now _know_ it needs fixing. But fuel is escaping from somewhere else.. somewhere lower down.

If, after sealing the banjo the carb still leaks, you gotta go deeper, probably into the float bowl.. see whats happening in there.

_Say the float needle does seat correctly and keeps gas from going into the carb. Where does that extra gas that sneaks out of the petcock go_

There will be no gas going anywhere if the float needle stops the flow. If you still see leaks, its coming from somewhere else, not from the needle. The leak will be somewhere between the float needle seat and the petcock.. a cracked fuel line, a leaking inlet (banjo?) gasket, a loose fuel line clamp, etc.

Re: Puch won't stop leaking gas

yeah.. the idea that the float doesn't float properly is a real possibility.

If it sinks, even partially, it may never float high enough to push the needle to the seat.

How do you test a float to see if it's floating properly? hmm.. i gotta think about this..

i'm gonna grab a beer and figure this out..

Re: Puch won't stop leaking gas

i can't think of a way to tell if a styrofoam float is partially saturated with fuel and/or oil.

A change in weight after drying would show the float weighs more than it should (and so will sink too far) but removing the float and drying it out completely is not possible if it has absorbed oil. Just resting it on a paper napkin or a dry coffee filter might draw out some oil..

If it is absorbing a large percentage of gasoline, that gas will eventually evaporate and the float will lose weight. Use an accurate scale (ask a drug dealer or someone who reloads ammo.. they will have a small grain/gram-accurate scale :)

A hairdryer will speed things up..

I gotta think some more about this.. there must be a really easy way.

Re: Puch won't stop leaking gas

hey.. dig this..


"..........The older model Dellorto with the white plastic floats do not seem to be affected. The black floats used in most trial bikes since the 1994 model year are marked '2.8 grams'. This marking on the side of the float is the actual weight when new. ...."

( i know you have a Bing but a float is a float.)

This page mentions two ways to test floats.. one is weighing and comparing to the weight marked on the float (??? i never noticed any marks but then i never really looked.. )

The other way is to see if it sinks too far in a jar of pre-mixed fuel.. This sounds easy but unless the thing really sinks it may be inconclusive. Read the page for details.

So, see it there's a mark somewhere on the float and compare that to it's current weight.

Re: Puch won't stop leaking gas

Ben Van Zoest /

joew, you summed it up, fix the lowest (leak) point first and work yourself up. Eventually the leak will be found.

I have got one too, whenever I come up my driveway fast the ped is airborne for a short distant. IF I forget to shut-off the petcock I have a fuel puddle later.

Re: Puch won't stop leaking gas

Scott Brockerville /

I never noticed a mark, but like you i never really looked. I dont think there is one, maybe at one time, but the float is pretty "old" looking. (all tarnished with years of gasoline?) I did do a check on its abilty to float at one point. I left it in the carb bowl full of gas. From what i can remeber it sank on the side where the clip attaches, i assumed just the weight of teh clip would sink it. When i let it float with the pin installed and held the pin at the level of gas, it floated pretty much flush with the level of gas. Meaning it was all under the surface, but it would float. I didnt know at the time if thats the way it was suppose to be or not? I still dont know? When i go out later, i'm going to do this test again, just to refresh my memory on how much it actually floats.

Re: Puch won't stop leaking gas

ok.. i just tried a float from a 11.5 mm Keihin carb off a Honda PA50.

It weighs 64 grains.. thats 4.15 grams.

this float has a number, "214" stamped on it's top. But 214 seems to be a part number and not an indication of weight..

(although 64 grains is about 2.6 pennyweights, which is closer to 2.14.. but who uses pennyweights?)

Anyway, i floated it by holding it gently by it's hinge pin in a jar of fuel mix. Approximately 3/4 of the float sinks, and 1/4th is above the liquid.

This is probably normal behavior among all floats. If so, the proper fuel level in a float bowl is _far_ below the bowl gasket.

This allows an easy way to check the needle's sealing ability. Just loosen the bowl's screws (or on a Bing unscrew the bowl a turn or two) turn on the petcock and let it fill with fuel. If the carb leaks from the bowl's seam, the needle is not sealing.

Someone should figure an easy way to see wtf is happening in a float bowl.. a transparent float bowl? hmm.. i got an idea.. similar to my fuel level gauge on my tank..

Just attach a transparent plastic hose to the bowl's bottom drain plug (if it has one) and loosen the drain screw. Hold the hose upwards and the level of the fuel will be seen.. But you can't see if the float itself is hung up and is allowed to actually float with this method. A transparent bowl would be nice.

Re: Puch won't stop leaking gas

Liz Nayadley /

Using joew's theory of a transparent bowl I used a clear plastic take out container. I used the screw where the main jet screws into the bottom of the bowl to mount the carb to an old lug nut (or any 14mm bolt would work) from my volvo so that it would set level while inside the plastic container. I placed it in a plastic container with the water level set well below the where the gasket seal would be and it held tight. (see attached image) The float needle closed up and did not let any water in. I took of the banjo and dripped some water and it just sat there all sealed up. Not sure if this is 100% accurate test but, it seems logical? Now maybe I can rule this out as a reason for the possible leak?


Re: Puch won't stop leaking gas

cool.. i like that..

ok, the float is floating free, as it would if the carb were assembled, and it closes the needle? No liquid can flow through the fuel line and past the needle? It sure seems like that float and the needle is doing it's job. ( There is one caveat. The height of the tank, above the carb, determines how much fuel pressure is on that needle. Test this setup with the end of a fuel line held up in position where the petcock would be.. about 12" above the carb, i guess?)

A petcock that won't shut off completely has no effect on this needle. This needle will maintain a proper float level even if the petcock is on full blast.. a dripping petcock is just another annoying thing that should be fixed eventually.

The question remains about exactly where the fuel is leaking from. In your first post you say it's dripping off the bottom of the float bowl. In subsequent posts you don't mention it again. Is fuel still dripping off the bottom of the bowl?

Does the bowl have a crack? Or is fuel running from somewhere else and down the side of the carb? Is there some reason you can't pinpoint the source of this leak?

It seems easy enough to do if that carb is off the bike. First assemble the carb, thoroughly clean and dry the outside of the carb ..and you can feed it fuel (or some liquid) through it's fuel intake... and sit there and watch closely.. Find the source of the leak.

Re: Puch won't stop leaking gas

Liz Nayadley /

I assembled the carb and and hooked up the fuel line to it. I turned it on full blast and let it fill up keeping close eye on all the parts. It started leaking from the gasket on the bowl and running down the sides of the bowl. When I turned the petcock to the off position and cleaned it up it does not appear to leak. (i ended up taking apart the petcock anyway because it has been twisting around and I reassembled it knowing exactly where the off position is- so it appears not to leak in the off position anymore) I think maybe the needle is letting fuel by it slowly. The banjo was dry and so was the area where the fuel line hooks up to the inlet. Is is possible to order just a needle and float for a bing carb?

Re: Puch won't stop leaking gas

damn.. if it leaks at the bowl gasket then the fuel level is too high.. and it must be coming from the needle. That float seems to float.

I have looked at a couple needle tips under a low power microscope and there's not much to see. Usually there's a slight indentation in the Viton where it seats against the needle orifice.. That seems normal and doesn't cause leaks.

The other part of this is the seat itself. If you havent closely examined it, do so. There's an outside chance that the seat is not perfect.. perhaps it has a little burr from someone poking a steel wire through it to clean it or something like that.

If you get the impression im not anxious to suggest you buy parts, thats correct. It just goes against my grain to buy parts before every other alternative is explored..

And anyway, i have no idea if Bing parts will be available. The last time i tried for a Bing on a Kreidler moped, i couldn't find parts. However with a helpful knowledgable parts-guy behind the counter, you might have success.

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