fuel blowing out carbs/crappy idle

[Orkazim]

72 Johnson 50hp...Problems, will not idle at all, tried and tried. The motor has new power pack new rectifier and new plugs. It needed these in order to run when I took possesion. Have rebuilt the carbs, have two sets of carbs that I've tried. What happens, and i can see it, is that fuel gushes up through the "venturi tube" (im supposeng thats what its called) and most of it comes out instead of going in. It's quite noticable when the throttle is disconnected and I "thwump" the throttle a bit. Any ideas? It will idle around 800 but not nicely, I assume it should be lower than that, although the FSM doesn't seem to state an idle anywhere that I can find.<br />Perhaps I have more than one problem? <br /><br />Appreciate the help!<br />Nic

 

[backdraft]

Re: fuel blowing out carbs/crappy idle

No-t, sounds like the float levels are too high. But first, I would check the float needle seat. nrvjb

 

[Cricket Too]

Re: fuel blowing out carbs/crappy idle

Is the fuel spilling up through the tubes at idle or only when you goose the throttle? If it is at idle, whatever idle you have, and the needle or needles are stuck open, your probably not running on all cylinders. I would pull those carbs back off, reset the float level and take a look at the needles and seats. Also I don't think you want to go any lower than 800 at idle, you should probably be a little higher. Good Luck.

 

[OBJ]

Re: fuel blowing out carbs/crappy idle

Hey Nic.....if ya' can "feel" it blowing out from the carbs, ya probably got some reed damage. This would let the pressure from the crankcase blow back out through the carbs. Something to look at if resetting the floats don't work.<br /><br />Good Luck!

 

[BRIAN03]

Re: fuel blowing out carbs/crappy idle

Broken reed valve.

 

[kenneths]

Re: fuel blowing out carbs/crappy idle

If you've had the carbs apart, make sure the low end and intermediate jets are not in the wrong place.........

 

[rickdb1boat]

Re: fuel blowing out carbs/crappy idle

OBJ and Brian, got to be it!

 

[Orkazim]

Re: fuel blowing out carbs/crappy idle

I will take a look at the the float level and seats again, in case I set them wrong. Any recommendations other than whats in the service manual? The fuel is blowing out at all times but when the throttle is goosed it gushes out(on the bottom carb more than the top) and when idling i can see it as little drops being pushed back out. Like I mentioned earlier, everything had been replaced in them, inclding the floats and needles. Any particular damage i should look for to the carb itself?<br /><br />I am sure it is not the reeds, as I thought this also, I inspected them and no damage was found physically. Could they wear out in some way? All the little leaves were seated fine.<br /><br />Thanks again<br />Nic

 

[rickdb1boat]

Re: fuel blowing out carbs/crappy idle

Reeds could be weak and not sealing like they should, allowing the blow-back. Check floats and let us know. "Gushing" out is usually not a sign of float problems, unless the float needle is stuck wide open allowing unlimited fuel flow. Try this first. What happens when you pump up the primer bulb? Does it still gush out the carb? And does the bulb ever firm up? If this is the case, definitly head to the Carbs! And are you saying it's coming out the venturi tube and or deep in the carb throats? If it's coming out the tube, it could very well be the float.

 

[R.Johnson]

Re: fuel blowing out carbs/crappy idle

On this particular motor, I would certainly check compression, if you have'nt already done so.

 

[rickdb1boat]

Re: fuel blowing out carbs/crappy idle

R.Johnson has a good point! First order of business is compression, especially since it sounds as though you just got this motor and it has never run right. Correct?