Lean Sneeze??

[brokeboater]

I have a 99 200 carbed Johnson that has up until this point run very well. While fishing this past Saturday I noticed several times when I would shift to neutral and let the engine a idle a few moments it would "lean sneeze" and shut off. It started back up everytime. I did go through the carbs a year or so ago to clean. I did not remove the plates behind the carbs due to all the linkages involved. Anyone have a suggestions what could be going on? I assume it would be a fuel issue?Thanks

 

[reeldutch]

Re: Lean Sneeze??

did it sneeze back threu the carbs or did it coufh treu exhaust?

it might be as simple as a air leak in the fuelsystem.
or a fuel restriction. vacuum
try to run motor with a remote fuel tank see if this stops the sneezing.
if so the problem lies in your fuel system before the engine.
anti syphon valve can get clogged especialy with ethanol and fiberglas tanks.
if not it lies within the engines fuel system.
make shure all the fuel line connections ar air tight.
use the propper straps or clamps.
if you are 110 % possitive there are no leaks it might be the carbs.
when it starts sneezing spray some 50:1 gas mixture threu carbs trought.
if it picks up its running lean at idle.
check the float for adjustment. in spec?
if the float is fine clean idle circuit very well.
make shure when asembling the carbs there are no other airleaks possible leaning out the fuel/air mixture.

check your compresion, lean engines dont live very long.

does it only do this at idle ?

why did you clean the carbs ?
same problem before?

how long do you have this motor.

hope to get you going in the right direction.

 

[brokeboater]

Re: Lean Sneeze??

wow. thanks for the reply.

carbs were cleaned as a matter of general maintenance after having set for a while.

i have had engine about 3 years.

it only does it at idle and only a few times that day. have not run it since except on the hose in the yard. didn't do it then.

did have a carb leaking fuel from the small hole just below the throat. i pulled that carb off last night and checked float level and for trash under needle. everything looked ok. can't tell if it will still be leaking till i get home this evening.

very familiar with lean engines not living long. ruined one years ago because carb ran a cylinder lean. :|

clean idle circuit??? can you expound on that please? i assume that will require removing the plate behind the carbs? that scares me a little. i do have the johnson manual but all that link and sync stuff looks like it may require some tools i don't have. is that something an average backyard do it yourselfer can do?

 

[reeldutch]

Re: Lean Sneeze??

before you start cleaning the carbs again and again and again and
it doesnt fix the sneeze, check the fuel system.
connect a 6 gallon tank to the motor.
make shure everything is air tight.
run it on idle in the lake (loaded)see if it still sneezes.
also in gear at lowest rpm.
if it does sneeze you might want to recheck the carbs.

get a plant sprayer and spray some mixed 50:1
in 1 carb at the time.
if rpms go up thats a lean idle circuit in that carb.

you got to do it step by step to eliminate problems.

 

[brokeboater]

Re: Lean Sneeze??

i will go over all the fuel line connections this evening. it ain't gonna be easy running this thing off a portable tank either but i'll give it shot.
thanks

 

[brokeboater]

Re: Lean Sneeze??

all fuel lines checked out ok. run it in a tank in the yard. pulled leaking carb and found a piece of trash blocking a small brass tube that extends down into the float bowl. that appears to have sloved the leak problem. also pulled all the other carbs and cleaned them and the idle circuit. i did not find any type of obtructions there. could the trash i found in the 1 carb have cause the sneeze?

 

[andy6374]

Re: Lean Sneeze??

Could have...

When you were don cleaning the carbs and you reinstalled them on the engine did make sure that the throttle shutters in the carb throats were fully closed at idle. This will cause a sneeze.

If not get some clear/transparent hose and connect it between the fuel pump and the carbs and check for air bubbles in the line. Keep moving this hose towards the fuel tank until you find it's source (that is, if there is an air leak somewhere).

 

[Walker]

Re: Lean Sneeze??

Check your idle timing, and link&sync. Things out of whack in those areas can simulate a lean sneeze. My 120 looper is real sensitive to idle timing
Test your recirculation valves as they can do the same.