Fab a diaphragm for a small engine Carb.

[Iplayfarmer]

Here's another pie in the sky question for others who ascribe to the theory of "Fix it up, wear it out, make it do, or do without."

I just picked up a sears 500 watt generator with a 1 hp engine. The diaphragm for the carbeuretor is blown, and I don't see it offered on the sears parts website. Can a guy get the material for one of these diaphragms and just cut one out like he can with gaskets?

 

[Iplayfarmer]

If it helps anyone, the sears model number on the housing is 580.328150

 

[davkir]

I don't know if this helps, but I had a similar problem on an old Sears power washer. It had a Briggs and Stratton engine.
I went to one of the large mower repair places near here and they not only could cross reference and match the number, but had the two piece diaphragm and gasket in stock!
I don't remember exactly, but it was only a couple of dollars.

 

[KubotaSam]

Sears never made anything themselves. The engine was made buy some other company. Take it to a small engine shop. They can probably tell you who made the engine and hopefully order you the parts.

 

[JC-jetro]

Here's another pie in the sky question for others who ascribe to the theory of "Fix it up, wear it out, make it do, or do without."

I just picked up a sears 500 watt generator with a 1 hp engine. The diaphragm for the carbeuretor is blown, and I don't see it offered on the sears parts website. Can a guy get the material for one of these diaphragms and just cut one out like he can with gaskets?

What do you mean with "diaphragm" in the carburetor? Is it part of a fuel pump? are we talking a gasket material maybe ? a thin piece of EPDM rubber can be used for a pump but usually they are .5 mil at least and pretty thick for diaphragm material. If we're talking gasket, for emergency situation I have cut out gasket material out of cereal box card board impregnated in engine oil. surprisingly it works well till you find real replacement. you can also get stock gasket material to cut out what you need with a very sharp exacto knife.

jc,

 

[KubotaSam]

What do you mean with "diaphragm" in the carburetor?

jc,

Many small engines incorporate a fuel pump into the carburator. The diaphram
does the pumping. It lifts the fuel from the fuel tank below the carb. Both Briggs and Stratton & Techumsec use them on certain models.

 

[JC-jetro]

Many small engines incorporate a fuel pump into the carburator. The diaphram
does the pumping. It lifts the fuel from the fuel tank below the carb. Both Briggs and Stratton & Techumsec use them on certain models.

Yes, You are right, my Briggs engine on my 5hp tiller uses diaphragm type fuel pump and the tank is lower than the carburetor so fuel must be pumped up. I just wanted to make sure I understood the original question right. A lot of diaphragm are very thin EPDM rubber material to allow pulsation hence pumping by vacuum caused by piston reciprocating. I have not been able to find thin enough rubber material to make my diaphragm yet.

Jc,

 

[Iplayfarmer]

Thanks for the replies everyone. Here's the plan...

I have some nitrile gloves. I'm going to try some nitrile glove material in addition to the old Diaphragm. The hope here is that the old diaphragm will provide the necessary rigidity and the nitrile will provide the seal. the diaphragm is broken just around one edge, so this just may work.

If that doesn't work (maybe even if it does), I'll try the local small engine repair guy. He's done pretty good at getting me parts.

 

[Redbug]

Iplay...That's a good idea about the nitrile gloves...I would never have thought of that. If the rubber is gas resistant... A lot of small engines use diaphrams in their carb designs. Especially the 2 stroke engines which power weedeaters, chainsaws, blowers, etc. Would you let us know how well the glove idea works? That's a good backup plan also when it's a Sunday and the parts places are closed...

 

[tommu56]

they usually are about $4.00

try Small Engine Parts - Briggs & Stratton Fuel System Parts

down the lower part of the page

tommu

 

[Treemonkey1000]

Most of the carbs are fairly similar from those size engines. I have salvaged carbs from other mowers and things to use for replacing carbs. Sometimes you may have to come up with a linkage for throttle or governor.

 

[Iplayfarmer]

OK, Scratch the nitrile glove idea. I tried it several different ways with no improvement. I tried it with the diaphragm, without the diaphragm, cut the flaps out of the nitrile, in front of the diaphragm, behind the diaphragm, on both sides of the diaphragm. In all instances I got better fuel suction with just the plain old broken diaphragm.

I can still see air and fuel leaking out from around the diaphragm, so I know that is a problem.

Tomorrow I'm off to see the small engine repair guy to see what he can do for me.

The good news is that when I drop a teaspoon of fuel into the spark plug hole the thing runs like a top for a few seconds.

 

[tlbuser]

Tomorrow I'm off to see the small engine repair guy to see what he can do for me.

The good news is that when I drop a teaspoon of fuel into the spark plug hole the thing runs like a top for a few seconds.

It was worth a try. good thinking. Next, if you can't get a pump diaphragm might be to move the tank above the carburetor, then it wouldn't need the pumping action.

 

[RavensRoost]

These guys may have it:

CM Small Engines
We carry obsolete parts for Homelite, Poulan, McCulloch, Briggs, Tecumseh and ATV's. Any 2 cycle or 4 cycle parts. We also carry Efco brand parts, Homelite trash pumps and parts for pumps. As well as Oregon chainsaw parts and bars. Visit us at cmsmallengines.net - Small Engine Parts Inventory For Sale MURRAY PARTS,TECUMSEH PARTS,MTD PARTS More.... or call 1-877-280-1624

RavensRoost

 

[border collie]

Innertube?

 

[Iplayfarmer]

Innertube?

I actually had the innertube sitting on the table ready to cut it, but I'm not sure how well the rubber would hold up to the gas.

 

[Iplayfarmer]

Strike 2...

I went to the local small engine repair guy. He put quite a bit of time into looking for the carb parts, but came up empty handed. He even went page by page through his book and didn't find anything like it.

I looked at the carb, and it's a TK carb. I looked up TK carbs. I didn't see anything that was similar to the diaphragm that I have.

I wonder if there's some way to re-surface or repair the diaphragm I have. You can see in that third picture where the surface of the diaphragm is torn.

 

[Patches]

I believe those elongated button looking thingys in the voids of the diaphram are actually valves that close off and open fuel channels. When one is closed, the other is open to fuel flow, and they are driven by engine vacuum(sic), or more precisely, by crankcase pulses caused by piston movement.The reason the nitrile fix didn't work was that the nitrile didn't move with the original diaphram, but remained against the carb body

 

[Treemonkey1000]

Those are flapper valves for fuel flow similar to the old floats in carbs that would shut off a full bowl of fuel. They need to be flexible enough to move with the small amount fo vacuum created in the carb and still seal. Inner tube would be too thick.
There has to be enough similar carbs that would fit that bolt pattern to come up with another carb that will work. I have done that on Chainsaws and mowers.

 

[Danno1]

I actually had the innertube sitting on the table ready to cut it, but I'm not sure how well the rubber would hold up to the gas.

.

I believe an inner tube is made of butyl rubber, which is not resistant to gas.

.