B&S carb overhaul questions

[crackerjack222]

I have ordered parts to overhaul the carb on a 20 year old Briggs & Stratton 4hp lawn mower engine. The carb float and needle valve just came in and I see a small rubber "cup ring" in the package with the needle valve. This is the needle valve attached to the float that regulates fuel into the bowl. I dont think I have ever seen that ring before. How does it mount? On the needle? Which way does the cup face? Toward the body of the needle or the point of the needle? The parts diagram does not show the cup. It will be a few days before I get back to the shop to assemble it.

 

[JRobyn]

Pictures? I don't think I've ever seen any kind of ring/gasket associated with the inlet needle/seat either except for a few that use a fiber washer under a replaceable, screw-in needle seat. If yours doesn't have it, don't use it. Most of the time, carb rebuild kits include parts for as wide a different model/serial number spread as possible, so it is common to have extra parts. Two-cycle carb kits are the WORST (best?) for this.

 

[Billrog]

I have a Briggs repair book so if I see a pic. I may be able to copy the page for you and post it.

 

[scdeerslayer]

Most of the time, carb rebuild kits include parts for as wide a different model/serial number spread as possible, so it is common to have extra parts. Two-cycle carb kits are the WORST (best?) for this.

I was going to say the same thing. Always have extra parts in chainsaw carb rebuild kits.

 

[RandyT]

I suspect you are talking about the viton seat. the divot will face toward the needle when installed into the recess where the needle fits. That may or may not be used on your carb. If your old needle valve has a viton tip/ aka rubber tip then you don't use that needle or seat. If you have the solid aluminum needle then the viton seat fits up inside where the needle valve goes.

 

[crackerjack222]

Thanks Randy, that makes sense. When I get back to it I will see if there is a viton seat in the body. I know the needle does not have a viton tip. I assume the viton seat is just pressed into place in the body?

 

[RandyT]

put a drop of oil on the seat and press it into the bottom of the hole with light pressure until is stops. Don't let carb cleaner get near that seat because it will swell or crumble.

 

[4get gto]

put a drop of oil on the seat and press it into the bottom of the hole with light pressure until is stops. Don't let carb cleaner get near that seat because it will swell or crumble.

Boy you would think those little rubber seats would be more resistant to carb cleaners than that.

 

[RandyT]

The Briggs brand spray carb cleaner like dealers use will cause it to crumble like a pencil eraser. Other brands can cause it to swell which causes it to either roll out of position or raise up and not let the float set level.