Cub Cadet sc621 Briggs engine-New carb but float keeps sticking

S

Steve23

Member
Once I get it running I'm got for the day. If I let it set all night and try to start it I find needle valve has closed. I take carb apart and don't see any dirt or particles anywhere. I re-seat the needle valve and blow it out just in case something is there, but it's just moving freely now. This is the 2nd time I've had to do this. If it happens again I don't know what to look for.
If anyone has an Idea I would greatly appreciate it.
 
Have you checked for free flow to the carb? Pull fuel line from carb, drain into a jar. It settles to the bottom. Does it flow freely, or dribble? If not free flowing, fuel lines/tank may have crud in them. Examine the fuel in the jar. Do you see any signs of water? If you've been cleaning the needle on that new carb, are you seeing any particles in the bowl? If there are any issues, replace fuel lines, with new filter, and shutoff. If still dribbly, blow into fuel line to tank. If that frees it up, the tank probably needs cleaning.

You've probably done this, examine the float/needle for any burrs or signs of anything that could hang it up.
 
Yes, I have already flushed the tank, replaced fuel line and filter, and even replaced gas with filtered gas. That is my next look to see if there may be a burr or a seat imperfection that may be hanging it up. I hope it doesn't happen again, but I'll let you know if it does and what I find.
 
I did want to mention that my primer bulb doesn't seem to be working anymore. When I push it there very little resistance. I took off the housing and held my finger over the primer hole while plunging. There was airtight resistance so I don't think there is a crack in the housing. I also doubled up on the gaskets and tightened to the carburetor securely, however the blub still has no resistance. Back to the carburetor again?
 
OK, I took my old carb. and cleaned it all out and made sure float was moving up and down freely. Now my primer works good, but one more thing. when I leave my mower set overnight it gets flooded by morning. Gas is still running into engine, so I have to remove the spark plug, flush the gas and I'm good to go. With a new float, needle and seat, I don't see how this can be happening. Gas is even dripping out of the little hole in the primer bulb. This original carb. works so good when running I hate to ditch it, but what else can I look for?
 
FIrst thing is install a cutoff in the fuel line. Second thing, if it's doing that, it's contaminating the oil. Hopefully we can figure out where the leak is and you can change the oil. You can test with a clear fuel line connected to the carb, that runs a foot or so higher than the carb. Fill the line, and see if it holds for 30 minutes. Probably won't at this point. You say new float, needle, and seat, is the seat installed properly? If you pull the bowl, and blow into a line attached to the carb inlet, and move the float up and down, does it stop/start flowing? Could something in the bowl stop the float from going up enough to stop the fuel? If you remove the carb, and turn it upside down, does it stop fuel flow?
 
Mark H_NO said:
FIrst thing is install a cutoff in the fuel line. Second thing, if it's doing that, it's contaminating the oil. Hopefully we can figure out where the leak is and you can change the oil. You can test with a clear fuel line connected to the carb, that runs a foot or so higher than the carb. Fill the line, and see if it holds for 30 minutes. Probably won't at this point. You say new float, needle, and seat, is the seat installed properly? If you pull the bowl, and blow into a line attached to the carb inlet, and move the float up and down, does it stop/start flowing? Could something in the bowl stop the float from going up enough to stop the fuel? If you remove the carb, and turn it upside down, does it stop fuel flow?
Click to expand...
Thanks!! That's very good info. For now, I have put in a fuel shut off and I will change the oil. I put on another carb that I know is good while I proceed to see what's going on with this carb.
 
Mark H_NO said:
Sounds good!
Click to expand...
Ok, I found the seat for the needle valve was disintegrated. I ordered a new needle, seat and float. I'll let you know what happens when I get it running again.

On a side note, I have tried 3 different after market carbs on Amazon. Although each one had the primer hole on the right side they would not primer, although my original primed just fine. Have you seen this? I can't understand what the difference is inside the carb to prevent the primer from working.
 
You can make your own primer bulb. Need to pressurize the carb fuel bowl. Barb hose fitting some hose and a primer bulb. When you hit the bulb, pressurized air makes gas shoot up into the venturi.

Or T off the fuel line into a primer bulb and hose going to a home made wooden carb spacer into another hose barb. When you hit the bulb it draws gas into the spacer into the intake port.
 
You must log in or register to reply here.
Back
Top