carb issues

[jasonr83]

ive got a 1990 johnson 70 hp. ive rebuilt carbs and they are still leaking gas out of the venturies. it stil runs good until it gets warm and then it doesnt want to idle. ive taken carbs back off and rechecked float level and all is well. im not sure where to go from here. it doesnt leak while pumping primer but leaks badly while running. any help would be appreciated.

 

[Cofe]

Re: carb issues

With the carbs upside down. The float should be exactly parallel with the carb body. For fuel to leak out the carbs indicates that the float needles are not closing all the way.

 

[SparkieBoat]

Re: carb issues

you may need to clean out the needle valve passage and/or replace the needle valves..cofe told you right about the float level.

 

[jasonr83]

Re: carb issues

I set the float levels exactly parallel. With the carbs upside down i cannot blow air through the fuel inlet, so i know the needles are closing all the way. It doesn't leak when i squeeze the primer bulb, which also tells me the needles are sealing. It only leaks with engine running.

 

[ONERCBOATER]

Re: carb issues

not sure but thinking your needles rubber tips may have taken a set, I can't remember but for some reason 2psi or 5psi resistance comes to mind when the carb is inverted and the float has closed the needle valve. you may be almost there but now quite enough. also when engine running vibration is present which may let a marginal seal leak there. When you rebuilt the carbs did you replace the needles or reuse them? I know a time or two where I have gotten addition time out of needle valves by soaking them in hot ATF.... not at all recommending this just noting that it worked in the past.
That said... if your carbs are leaking fuel via the jets it can be fairly certain that either the float isn't set right or the needle valve is leaking for some other reason.
I believe the reason it is running good until warm is that while cold it can use the richer mixture but as it warms up the extra gas is creating an over rich mixture.

Sean

 

[jasonr83]

Re: carb issues

ok today i got a better look at carbs after resetting floats for the third time. the fuel leak appears to be coming from the tops of the emulsion tubes. This would explain why the leak doesnt occur when pumping primer. If the needle and seat where the issue it would leak while pumping primer. The needles are sealing tight and im pretty sure its not a float problem. But ive never seen an emulsion tube leak before. Im gonna try to seal them in am and see what happens.

 

[Cofe]

Re: carb issues

I have heard of loose tubes before, but I don't know anything about what to seal them with. What are you planning on using to seal them?

 

[jasonr83]

Re: carb issues

I found a sealer at the parts store that is similar to super glue but it resistant to gas.

 

[jasonr83]

Re: carb issues

Ok it appears that the emulsion tubes are not the problem. Gas is spewing from two very small holes just before the throttle plate. idle passages??? My carb diagram is not very specific in this area. My question is why is gas leaking here and what should i do to stop it. This is happening on all three carbs. (probably something i didn't get right during the rebuild) Engine did not run when i got it so i dont know if this was happening before i rebuilt the carbs or not. There is also a screw on the top of the carb body in the front, when removed there appears to be a jet in the back about 2 inches deep. my carb diagram doesnt even show this at all, and i did not remove these during the rebuilds. I didn't know they were there until afterwards. maybe problems there???

 

[SparkieBoat]

Re: carb issues

is that where the injector (choke) squirts in fuel? the little red valve on your injector pump open?? or maybe injector pump stuck on because of short or bad key switch, try disconnecting the wire going to it and see if leak stops.

 

[boobie]

Re: carb issues

Did you put new needle & seats along with gaskets in the carbs when you repaired them??

 

[jasonr83]

Re: carb issues

its not the choke injector, i disconnected anyway and no change. the choke injector is behind the throttle plate. these two very small holes are in front of the throttle plate just behind the emulsion tube. I did change needle and seat and they are sealing. i can pump primer bulb until rock hard and it holds and no fuel leaks out of carbs. that should mean that needles are seating fine. carbs only leak after i start engine, they immediately start dripping from all three carb throats. i will try to upload a picture, but i dont think you will be able to see anything because they are so small.

 

[SparkieBoat]

Re: carb issues

that is a new issue to me. only thing I could think of is there is a bad seal/gasket or something has been left out of the carbs after a rebuild maybe..I have never seen what you describe, unless it was the needle valve/float issue.

 

[jasonr83]

Re: carb issues

Im still not acually sure what the problem was but it seems to have almost fixed its self after i ran it on the river a few miles. i was adjust carbs afterwards when i noticed gas was no longer leaking out while running. I let it idle for 30mins with no problems. i noticed a little bit of gas leak out when i shut it down and tilted engine up. But it started right back up when i tried so i can live with that. Ive got one more question Does the idle mixture go rich or lean when i turn the screw out? It seems to lean out when i back the screw out. For some reason that seems backwards to me, but i am usually working on a car carb. thanks guys