[samahi72]

Okay Tecumseh is probably just trying to confuse the daylights out of me. (It's working)
I picked up a mower and the bulb is missing. It is a 4 H.P. and I have a choice of 4 bulbs.
1. Hole in bulb with what I call an accordian pleat.
2. No hole in bulb with an accordian pleat.
3. Hole in bulb, with just a plain bulb- looks like a dome.
4. No hole in bulb, with just a plain bulb.

They all appear to be the same diameter and I am sure the hole is there for some reason but
1. How do you know if it was designed to use a hole or not?
2. Will the bulb style and the accordian style interchange (as long as you interchange a non hole accordian style with a non hole dome style, or a hole with a hole style)?

 

[Brad]

The hole in the bulb will be to help vent the carb. What machine is this for, and do you have the engine model number?

 

[samahi72]

The hole in the bulb will be to help vent the carb. What machine is this for, and do you have the engine model number?

Hi Brad
Actually my question was more generic than specific. While I do have one mower that needs the bulb, what I would really like to know is will the accodian style bulb interchange with the dome style bulb?

Is there some chart or website that you know of that shows the bulb style?

 

[Brad]

Sorry, that I could not answer. I have a hunch that the dome styled bulbs would be a smaller circumference that the accordion type, but I'm not sure.

 

[Mark / Ohio]

I've always figured the bulbs with the hole prime the carb when pressed with a finger over the hole. Bulbs without the hole prime the car as it is expanding back out after depression.

I would think the bellow design would have more rigidity then the dome design. Thus they might also provide the carb prime on the return expansion with the bellows acting like a return spring.

I don't really know, just theorizing. Safest bet it still to get a replacement based on either engine or carb brand & model numbers.

 

[samahi72]

I've always figured the bulbs with the hole prime the carb when pressed with a finger over the hole. Bulbs without the hole prime the car as it is expanding back out after depression.

I would think the bellow design would have more rigidity then the dome design. Thus they might also provide the carb prime on the return expansion with the bellows acting like a return spring.

I don't really know, just theorizing. Safest bet it still to get a replacement based on either engine or carb brand & model numbers.

Thanks for the input Mark.
I do know from experience that if you put a bulb with a hole in it on a carb that was meant to have a solid bulb, it won't run. The hole causes some of the vacuum to escape to the extent that it will not draw up the fuel from the fuel bowl.

I also agree that it is best to get a replacement bulb based on the brand and model number. I was just thinking that there has to be some type of "Master Chart" that will list which model/brand uses which style bulb.
Steve

 

[twocycle]

Tecumseh Quick Reference Service Guide..... http://www.smallenginesuppliers.com/html/engine-specs/tecumseh/Tecumseh_quick_reference.pdf

Tecumseh Carburetor Identification, Troubleshooting and Service Manual..... http://www.barrettsmallengine.com/manual/tecumsehcarburetormanual.pdf

Tecumseh Technicians Handbook..... http://www.allotment.org.uk/assets/rotovator/Tecumseh-Engine-Manual.pdf

 

[oldyellr]

Thanks for posting these links twocycle. This thread is almost 2 years old and I wouldn't have seen it otherwise. It appears that the OP has a Tecumseh with the primer bulb built into the carb. I have an old snowblower with a 5 hp Tecumseh and it's very frustrating to start after it hasn't run for a while. It has a remote primer bulb without a vent that connects to the float bowl. Near as I can figure out, it just blows air into the float bowl in an attempt to jiggle the float and cause a little bit of flooding. I've checked the bulb and connecting hose and there are no leaks, but even 100 pumps of the bulb have little effect. It's faster just to remove the plug and pour a slug of gas or a shot of ether into the cylinder.

Reading from the Tecumseh Technicians Handbook linked above:

Two different methods are used to prime float style
carburetors, leg prime and bowl prime. The leg prime
system is used only on the dual system carburetor. Air is
forced into the center leg of the carburetor, which then
forces an enriched mixture of fuel up the main nozzle. The
bowl prime method is used on Series 6, 8, 9 and 10
carburetors and is distinguished by a stepped or hour glass
shaped primer bulb. A good seal of the primer bulbs center
lip is critical to assure that a full charge of air reaches the
bowl. Also critical is a tight seal around the float bowl.

... the only thing I can think of is leaky float bowl gasket. Opinions?