Leaky carb, why?

[kauboy]

I recently rebuilt my carburetors and found that the inner gasket in the bowl was cracked in the lower carb. I replaced it as well as the other gaskets.

Well, I cranked the engine up today in order to properly adjust the low speed needle, but when it was running, fuel was seeping from the small hole just above and to the left of the air intake. This fuel was dripping down and being sucked into the engine, causing the whole thing to rev up each time.

I couldn't adjust the needle to any setting that would stop this leak. Maybe thats not even what I should have been doing, so I decided to ask here.

Here is a picture of the hole where the fuel was bubbling from:

Any ideas on what to do next guys? Should I disassemble the carb again and recheck everything? The other two carbs didn't give any problems and would be easily adjustable if I could just keep the fuel from sucking back in and revving the engine.

Thanks for any help you can give. I love the wealth of knowledge available here. You guys really know your stuff.

 

[jtexas]

Re: Leaky carb, why?

what motor is this? year/hp.

I'm guessing a core plug

 

[kauboy]

Re: Leaky carb, why?

Year: 1969
HP:55

Whats a core plug?

 

[jtexas]

Re: Leaky carb, why?

in your carb rebuild kit, were some round metal discs, shaped like a contact lense - there's one on top of the carb body - if you didnt' take the old ones out then I'm probably wrong, they don't generally just "spring a leak".........

 

[kauboy]

Re: Leaky carb, why?

I saw those in the kit, but was told that as long as air could be blown through the passage ways, it wasn't always necessary to replace them, so I didn't.

It seems like this hole is supposed to be a type of overflow path, but I don't know what is overfilling.
Think maybe my float is not set properly?
Would the bowl overfill and spill out of this hole?

 

[jtexas]

Re: Leaky carb, why?

right, those are access holes for cleaning out passages.

I believe that hole is your idle air bypass circuit - with the throttle plate closed, the piston movement creates a vacuum in back of the carb throat which should be drawing air in through there. Since there does appear to be good vacuum at the front of the carb, I assume that means the reed plates and the carb-to-intake gasket are ok.

Any chance the actual leak is at the float bowl gasket (or elsewhere) and its dripping between the air silencer & carb body giving the impression that the leak is there? just a thought.

Or, a tiny piece of that cracked gasket could've got up in there, partially creating a blockage.

What I would do is, first, make dang sure the gas is truly leaking back out that hole (which you may already have done)..........then, go ahead & take the core plug out - there's one on top, your carb *might* also have one on the roof of the carb body which leads to that particular hole (mine does but it's a few years later model 3-cyl). Blow compressed air through all the holes under there.

Try to avoid 'punching' through it and hitting bottom with the drill bit, but you've got nearly a half-inch clearance underneath, and unless you hit really hard its very unlikely to hurt anything. Small hole then pry it out with a sharp tool or a tiny screwdriver or something.

good luck....................................

 

[kauboy]

Re: Leaky carb, why?

I appreciate the response, but I'm not sure I properly explained what I am seeing.

When I used the term "leak", that may have been misleading.
I'll try again.

When I start the engine(flusher on, and all that jazz), fuel and bubbles start coming from this hole. Its not coming from any seals or gaskets. Its just dripping from the circled hole(in the pic) and then being sucked into the intake. When you look to the side of the carb, the passage looks like it runs straight back, and then straight down into the bowl. This is what has me thinking that the bowl may be overfilling. And yes, there is a disc located at the top of that passage, but since air and fuel are passing through it, I can't imagine anything blocking it.
Under normal operation(above idle) I'm sure it would work fine. Even if it did leak, the fule would be caught in the air silencer hose at the bottom of the assembly and be re-introduced to the system. But since I haven't had it on the water yet, I haven't gotten a chance to try it.

 

[jtexas]

Re: Leaky carb, why?

the hose at the bottom of the silencer is there to recover the engine oil that collects on the silencer cover, and deliver it to the lower crank bearing. During normal operation fuel doesn't leak out through the idle air bypass. If the passage you described leads to an opening on the roof of the bowl..........check another carb to be sure, but I believe that opening is supposed to be plugged. See if there isn't a core plug in the kit that is smaller than either of the plugs on the outside of the carb (one right up on top, another on top facing the starboard side), but that fits the opening to that passage.

Two ways to tell if the float valve is sticking open: 1 - tilt the engine up far as it will go (engine not running), squeeze the primer bulb - if you see any fuel running out the carb throat, the valve is stuck open. 2 - hold the carb upside down and blow through the inlet (best to drain the bowl before attempting this...or else acquire a taste for 2-stroke mix ) - if any air gets through, the float valve is stuck open.

 

[kauboy]

Re: Leaky carb, why?

Ooooo!!
I like that tip. I will give that a try. I honestly believe that the passages are fine, but if the inlet test proves nothing, I may eat those words.