B&S carb float sticking?

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  #1  
Old 12-07-09, 09:11 AM
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B&S carb float sticking?

Have a 21 horse V-Twin I/C B&S Engine Model 4045A7 on a Murray 465306x8 garden tractor.

If it matters: type is 0211 E1 and Code is 031103YG

I'm having constant starvation problems when the tractor has not been run in a while and occasionally during start and stop engine operations.

Always starts with starting fluid and when it does run off the gas tank it runs smooth and never quits. When it is not starting I often seem to able to solve the problem by tapping the carb with a hammer that makes me think the pin is hanging up in the seat.

I've seen some carbs do this, but obviously it doesn't happen every time.

Don't know if this just says replace the needle and seat anyway. Or if there is any additive I could put in the gas to minimize sticking of the needle on the rubber seat or?

Would also be interested to find out if anyone makes a permanent or test bowl for these carbs that is clear. Then I could actually observe what the hell is going on. (Kind of like a temp plexiglas door for a dishwasher which is how we figure out performance problems with dishwashers).

Also, I can't help but be interested in the theory of ops for these carbs with some kind of magnetic solenoid where the jet adjustment screw used to be. I have several of these in service and don't think that carb adjustment or the functioning of this solenoid has ever been a problem but the whole thing is kind of black box to me at the moment compared to the accessibility of the old adjustment screws. So some kind of primer on what this is actually doing. Is it some kind of fuel shutoff or a governor . . . ?

Thanks,

Brian
 
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  #2  
Old 12-07-09, 10:11 AM
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The solenoid could be an issue.
I have heard them called "anti-backfire" solenoids originally. They are a fuel cutoff.
When the key is turned to the "on" position, the solenoid should be energized pulling the plunger down allowing fuel to the main jet.
You could have a sticking plunger or a bad connection.
They are easy enough to test.
Drain the fuel from the bowl, remove the solenoid from the bowl. Connect the connector to the solenoid...if only one wire to the solenoid, then it will need to be grounded to the threaded portion of the solenoid. Turn the key to the on position, the plunger should retract without hesitation.
If there is still doubt, I have use a bolt with matching threads to that of the solenoid for testing purposes.
 
  #3  
Old 12-07-09, 10:20 AM
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I fix sticking and dragging needles by polishing the sides of the float needle and the hole the needle sits in using a Q-tip saturated with metal polish.

Sea Foam is a popular fuel additive to stabilize fuel and prevent varnish.
 
  #4  
Old 12-08-09, 10:59 AM
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thanks

that is the second mention of seafoam I've gotten so I'll be picking that up. the last time I had a needle sticking problem I didn't really associate with any evident varnish or other contamination, it was just hanging up in the rubber seat. But for seasonal implements I'm sure I can't go wrong with that kind of additive. I don't know if this carb has a brass seat or a rubber o-ring or rubber washer seat for the float needle.

Guess I'll have to break down and break down the carb. I was kind of hoping to run some cleaner through but I feel like I ought to see if I can figure out if the float needle or the anti-backfire needle is the one sticking. sounds like the symptoms would be more or less identical.

This unit appears to have a vacuum driven fuel pump and the tank is on about the same level as the carb although there is no shutoff. I think when the tank is full it would run gas if I disconnect the carb but it's at half now so I can do it without crimping the gas line off. I'm assuming that if I crank the engine that will create enough flow to test the fuel pump.

Thanks,

Brian
 
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