Float valve seat

[Kestas]

I have a snowthrower that was recently repowered with a used engine. I tried using it after the last snowstorm, but it wouldn't behave. I narrowed it down to a fuel delivery problem. Furthermore, I narrowed it down to the float valve seat (the tiny round insertable orifice piece), which is loose and sometimes drops out when I take the carburator apart. I believe it drops down and plugs the fuel flow during use, from the heavy vibration when the unit is running.

What can I use to permanently seat the valve seat? JB Weld, or is there a better technique? The piece looks to be ceramic.

 

[AandPDan]

Some carbs have a little retaining clip to hold the float needle in place, other's don't.

Normally, if it falls, or "drops down" it OPENS the valve to let fuel into the bowl.

It needs to pivot. You can't "weld" it in place or the angle will be off.

What make is this engine?

 

[TylerL]

I was gonna say solder it but then I saw the part about it not being metal. I'd say any two part chemical resistant epoxy would be the easiest solution.

 

[Zaedock]

If you epoxy the float valve in place, your carb will not get any fuel at all.

It's supposed to move up and down as fuel is used from the bowl.

It sounds like it's not being retained to the float. Look for the clip, or sometimes the metal float pin has a retainer built into it. Also, any thrower carb I have seen has the needle seat up, so if it's dropping down, then there is no fuel level control and raw gas would be sucked in the engine, flooding it.

 

[Donald]

Originally Posted By: Kestas
I have a snowthrower that was recently repowered with a used engine. I tried using it after the last snowstorm, but it wouldn't behave. I narrowed it down to a fuel delivery problem. Furthermore, I narrowed it down to the float valve seat (the tiny round insertable orifice piece), which is loose and sometimes drops out when I take the carburator apart. I believe it drops down and plugs the fuel flow during use, from the heavy vibration when the unit is running.

What can I use to permanently seat the valve seat? JB Weld, or is there a better technique? The piece looks to be ceramic.


I think you might be a little mixed up on your terms and how a carb works.

Float - its brass or plastic and filled with air (sealed). Its hinged and can float up and down somewhat. It has a little metal paw that the float valve rests against.

Float valve (Float valve) is a small piece of machined metal, the upper end is machined to fit into the seat.

Float valve seat - is machined into or pressed into the carb. The float valve fits into it.

The fuel inlet is above the float valve seat and allows fuel to come past the seat if the float valve is not closing off the path for the fuel.

The float (once the carb is filled) moves up and down a tiny bit, just enough to allow the float valve to drop a little and allow some fuel in. That fuel will raise the float and shut off the fuel. As the engine runs fuel goes out of the jets and drains the fuel in the bowl, and more is let in.

The carb needs a very exact level of fuel for things to work right and that is what these 3 things provide.

If the float is no longer air tight (has fuel in it) it should be replaced.

If the float valve (where it touches the seat) does not look perfectly machined it should be replaced.

 

[JimPghPA]

If it is the doughnut shaped little float valve seat as OP said, then the thing to do is get a new one and press it into where it belongs.

You need to get the carb rebuild kit. There are many small engine parts companies on the internet. Partstree is a good one.

 

[doitmyself]

I imagine that Kestas is talking about a piece similar to the one on the left of this picture:

One solution might be to use a punch on the barrel of the float seat in three places equidistant around the circumference to SLIGHTLY deform the metal to cause a tight fit. OOPS! EDIT...if ceramic, then option 2 is the only one.

The other option would be to use a punch around the female opening that receives the seat, again to SLIGHTLY deform the metal to cause a tight fit.

I am talking about deforming the metal 1 or 2 thousands of an inch, not applying gorilla force.

You may still want to use some type of gas proof sealant (Permatex 2?) to seal the barrel in if there is no gasket.

 

[Kestas]

I thought I was redundant enough in my post to explain the problem was with the seat (small pink part in the lower right of picture) and not the pintle. The seat is too far down in the bore to perform any staking operation. The only other option is to either glue the seat into the bottom of the bore or to get a rebuild kit and hope the new seat has an interference fit. All other parts in my carburator look healthy and operational.

 

[cronk]

That looks like a Tecumseh carb.
I just rebuilt mine yesterday! The seat is made of a rubber like material. If yours is falling out it has probably dried out and hardened and shrunk. The rubber seat should be a snug fit and not be able to move around once installed. Buy the kit like you have pictured. I use the back end of a drill bit (the flat end) to press the new one in place. Usually compressed air will blow the old ones out.

 

[Quest]

Yes, that is a valve seat made of either viton or neoprene (most likely viton).

You'll need this tool (I have it for servicing both Tecumseh and B&S --Walbro carbs):

http://www.ebay.com/itm/670377-Tecumseh-...=item1e72bd5283

Q.

 

[Zaedock]

The drill bit method that cronk mentioned works pretty well for pressing in the new seat.

 

[JTK]

What holds the seat in place from the factory? I just *assumed* they were an interference fit. If they shrunk, they can pop out. Guess I'm lucky. Never had to mess with one before.

Joel

 

[Quest]

yes JTK, it is "interference fit".

just a pc of elastomeric seal.

Q.

 

[Kestas]

This all makes sense. The engine worked fine during demonstration when I bought it 20 months ago, and worked fine after I finished rebuilding the showthrower 16 months ago. Since then, I've stored it dry, and the seat must've dried out and shrunk, giving me the problems I'm having.