5.5 Carb - What's this hole for?

[CGaul]

This is a stock carb off a 5.5hp Briggs. This is the air inlet side. What is the hole that the arrow is pointing to for? The filter adapter I have will cover it and I'm wondering if that will be a problem. If so could I just drill out the hole on the adapter and all will be well? Thanks!

 

[Doc Sprocket]

I think that's a vent, but I'm not overly familiar with that carb. I would be inclined to leave that open to atmosphere.

 

[klicky96]

It is a vent. Usually, the gasket will cover it up. It's only there to let a small amount of air in.

 

[CGaul]

I did put my finger over it when the engine was running at a high speed and it did make it sputter. It didn't stall but, it wasn't running well either. I think I will drill out the adapter just to be safe

Thanks!

 

[Doc Sprocket]

You may not have to drill the adapter. Since that is just an atmospheric vent, I would suggest that you just notch the gasket around it. Picture a gap in the gasket that allows it to breathe "outside" air. If there is no gasket supplied with the adapter, I would make one.

 

[spyder1968]

was the gasket covering that hole originally?

 

[Doc Sprocket]

was the gasket covering that hole originally?

If I'm interpreting things right- she got the engine with an entirely different carb, (which she can NOT use due to class restrictions) and therefore purchased this carb to meet the requirements. That said, she's completely in the dark on this one.

 

[spyder1968]

Sorry, I didn't catch that part. If it were me, I would drill a matching hole in the spacer and try it. If it turns out that was a bad idea, you could always get a new gasket (or make one) that covers the hole, or possibly fill it with a good epoxy. JMO

 

[CGaul]

Yea, that is the correct story. The car came with a Mikuni carb which is illegal for the class my daughter is running in. So I am completely in the dark about what the original motor had. I'm also having to try to reconfigure a throttle.

 

[Doc Sprocket]

Well, whether you notch the gasket or drill the adapter, leave it open to atmosphere.

 

[Svend]

I agree, I think it is a vent too. I think it is a pollution requirement. If so, It vents crankcase vapors back to the carby so that they go through the system and get burned off. Wouldn't bother with it myself.

 

[Doc Sprocket]

No, it's not a PCV vent. Crankcase vapours go thru a rubber tube from the rocker cover to the air filer housing.

 

[CGaul]

Well, that hole definitely needs to be open to the air inlet. Closing it causes the engine to stall, then after it stalls you get fuel overflowing out the inlet.