Late 31 Side bowl filter Zenith carb question?

L

Late31ugh?

Junior Member
Hi I replaced the side bowl on my late 31 Zenith carb this weekend. Prior to replacing the side bowl the carb only leaked from the drain. Now gas is running out the carb intake. The only difference between the old and new part was the thickness of the two fiber washers on the filter bolt. Because of this the filter bolt is about 1/8" further into the carb. If the filter bolt is in too far in will it interfere with the float bowl or block a passage? If it is not the filter bolt i'll be tearing it apart this week to recheck the basics.
 
shut off the fuel ,run untill carb out of gas turn fuel back on start ---this will flush debris out of needle/seat, repeat if doesn't work first time.
 
Did you replace it with a repo? If so, I’ve found the reps to be problematic. The faces on the bowl are not exactly parallel to each other. The mating surfaces to the carb body and the bolt side don’t match up well enough to create a good seal.
Hope I’m expressing my though!
 
Yes, it was a complete replacement kit from a good supplier. The drain on my original had been overtightened sometime long ago and never properly sealed. If it is the mating surface that is leaking would the gas run down the carb and mimic a stuck open needle valve?
 
You may have knocked some crud loose and now the float valve needs cleaned. Remove the lower half remove the float and seat clean and reinstall. Try what Kurt said first you might get lucky!
 
No matter who you bought it from…the same people likely makes it for everyone.
That issue was just my experience, twice.
So I quit using repos
 
Late31ugh? said:
Hi I replaced the side bowl on my late 31 Zenith carb this weekend. Prior to replacing the side bowl the carb only leaked from the drain. Now gas is running out the carb intake. The only difference between the old and new part was the thickness of the two fiber washers on the filter bolt. Because of this the filter bolt is about 1/8" further into the carb. If the filter bolt is in too far in will it interfere with the float bowl or block a passage? If it is not the filter bolt i'll be tearing it apart this week to recheck the basics.
Click to expand...

Oldbluoval said:
Did you replace it with a repo? If so, I’ve found the reps to be problematic. The faces on the bowl are not exactly parallel to each other. The mating surfaces to the carb body and the bolt side don’t match up well enough to create a good seal.
Hope I’m expressing my though!
Click to expand...

Not sure how this would cause gas to leak out the throat of the carb. Leak at the connection, yes. I think some debris got in your float needle as Kurt in NJ suggests.
 
Follow on question spurred from the posts above. Is it possible to correct the inner mating surface of the drain has been distorted a will not seal?
 
I would take a brass rod the same diameter as the valve. In a lathe cut the end to the same angle as the valve tip. If a lathe is not available, use a drill press and file to make the angle. You want to simulate the valve tip. The coat the rod end with very fine lapping compound 1000-1200 grit. Insert and slowly turn it to lap the seat. Be sure to thoroughly clean out all lapping compound afterwards!
 
I’m having lots of problems with two rebuilt Zenith carburetors I have purchased recently. I also replaced the side bowl and have an in line paper filter. I’ve tried everything and cleaned the float needle valves repeatedly and still can’t stop gas from coming out of the over flow hole/ vent. Finally I cleaned out a spare rusty core with a the existing float needle valve, probably 5 or 6 years old. I put it on the engine and ran it a few times and , scratch my head, there is no gas coming out of the over flow/ vent hole. I’m going to put the old float needle valve in the rebuilt carb and see what happens and also put the new float needle valve in the rebuilt and see what happens. Also I’m going to rebuild a Tillotson. I wish I never spent the $325 for the professionally rebuilt. The core I sent out was just about as good.
 
Gino said:
I’m having lots of problems with two rebuilt Zenith carburetors I have purchased recently. I also replaced the side bowl and have an in line paper filter. I’ve tried everything and cleaned the float needle valves repeatedly and still can’t stop gas from coming out of the over flow hole/ vent. Finally I cleaned out a spare rusty core with a the existing float needle valve, probably 5 or 6 years old. I put it on the engine and ran it a few times and , scratch my head, there is no gas coming out of the over flow/ vent hole. I’m going to put the old float needle valve in the rebuilt carb and see what happens and also put the new float needle valve in the rebuilt and see what happens. Also I’m going to rebuild a Tillotson. I wish I never spent the $325 for the professionally rebuilt. The core I sent out was just about as good.
Click to expand...

I would send it back to the professional rebuilder first thing
 
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