gas in crankcase

bdunegan

Member
have a 21hp B&S single cylinder that keeps filling the crankcase with gasoline. I have taken carb off and cleaned it, cleaned fuel solenoid, and it is working(don"t know if shutting off all the way tho) cleaned needle valve and float, even changed fuel cap on the tank, but if left setting overnight, it will pull gas out of tank into crankcase. definitely putting an inline shut-off valve on it, but would like to correct carb problem!
 
You could try a new needle and seat.

The carb might be cracked internally from frozen water in gas. Very rare but sometimes there is nothing I can do to repair a carb. Used parts place or Ebay for a replacemnt.

If the needle has a rubber tip, then the seat is solid metal. You should be able to buy a replacement seat for it. It is tricky removing it and pressing new one in.

If the needle is solid metal, then the seat should have a rubber seat inside the brass bushing. The needle and rubber seat should be replaceable.

This is how I check the needle and seat. I am not sure what the carb looks like on that 21hp but this is how I check on smaller engines. With carb off, inline fuel shut-off to closed. Remove carb from block. Remove bowl. Blow the needle and seat dry with air. With carb upside down(bowl off), turn fuel on. Watch for where wetness is coming from.
 
I have one with a bad seat. Doesn't matter how many times you replace the needle - it won't help.

I just shut off the fuel when I park it.
 
Does this engine have a pulse (vacuum) operated fuel pump? problem could be there if the diaphragm has a pinhole in it.
 
When you had carb apart did you check float level?

Fix may be as simple as float out of level & gas leaking into carb venturi & cyl/crankcase before gas in bowel raises float high enough to shutoff float valve completely,other possibility is you have a bad float,there have been some cases of plastic floats being affected by ethanol content of gas.
 
1. I don't ever try to re-use carb. needles. Almost like asking for trouble. The seat is the other part of the equation and it is prone to damage too. Especially if ethanol is present in your gas.

2. Your best bet is a new carburetor. Get a Nikki for it if you can. Briggs tends to swap back and forth between Walbro and Nikki and a Nikki might not be available this month.

3. If you by chance already have a Nikki carb. on it, the float level is permanenty set and yes, it does look wacky angled up like that.
 
took carb off and took it apart one more time, and there was a tiny chunk of rubber in the seat not letting needle valve close all the way. come to find out, fuel line had come apart on the inside and sent tiny chunks of rubber past filter in to carb. so cleaned carb completely one more time, took tank off and cleaned it, and put all new fuel line and filter on it. so far been sitting since Saturday night with same amount of gas showing in tank! also put on the old failsafe shut off valve in the fuel line. Thanks for all the replies!
 

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