Yerfdog 3206 Spiderbox vacuum petcock

[Jport]

I bought a yerdog 3206 with a howhit engine used and got it sort of running. It doesn't idea well and takes a while to warm up it seems, but it does seem to go when you get it running.
I think the previous owner removed the vacuum petcock because there is a T in the vacuum line but nothing goes on one leg of the T. There doesn't seem to be a vaccum petcock, but there is an inljne shutoff valve in the fuel line from the fuel tank to the carb Iike you sometimes see on a lawnmower. My question is, is it supposed to have a vacuum petcock? And does it actually need a vaccum petcock if it has a manual fuel shutoff? Can I just cap off the unused leg of the T?
Thanks
Jeff

 

[Denny]

I would think you could cap off the unused end of the t. But I don’t have a lot of experience with those engines.

 

[madprofessor]

I never even heard of a vacuum petcock. In all of my experience, a vacuum between the fuel cell and the intake is the last thing you want, leads to vapor lock. Gas tank caps are vented for the express purpose of not being able to draw a vacuum on the tank, stopping the gravity flow or otherwise. If you required a vacuum there, how would you ever be able to use a fuel pump?

 

[Jport]

I would think you could cap off the unused end of the t. But I don’t have a lot of experience with those engines.

I never even heard of a vacuum petcock. In all of my experience, a vacuum between the fuel cell and the intake is the last thing you want, leads to vapor lock. Gas tank caps are vented for the express purpose of not being able to draw a vacuum on the tank, stopping the gravity flow or otherwise. If you required a vacuum there, how would you ever be able to use a fuel pump?

Maybe I'm using the wrong term. It's a petcock valve that let's the fuel flow when it's operated by a vaccum. I don't think it adds vaccum to the tank. I'm not sure why it would need to shut off the fuel flow.

 

[ezcome-ezgo]

The petcock on most small engine fuel lines is a valve designed to stop gravity mostly. As gravity demands, the fuel wants to leave the tank, but the petcock can be closed to put a stop to that nonsense when desired.

 

[Denny]

Go back to bed Mad. The scooters and karts with the gy6 style engines have an automatic fuel shut off valve on the gas tank called a vacuum fuel shut off. When the engine is not running it will not allow fuel to flow to the float bowl to cut down on chances of drowning the engine in fuel. It is just like the manual one on the bottom of a motorcycle gas tank.

And Mad before you ask, no you can’t use the vacuum on your carpets!

 

[Jport]

Go back to bed Mad. The scooters and karts with the gy6 style engines have an automatic fuel shut off valve on the gas tank called a vacuum fuel shut off. When the engine is not running it will not allow fuel to flow to the float bowl to cut down on chances of drowning the engine in fuel. It is just like the manual one on the bottom of a motorcycle gas tank.

And Mad before you ask, no you can’t use the vacuum on your carpets!

Do you think it's ok to just use the manual petcock and cap off the vaccum T?

 

[madprofessor]

When the engine is not running it will not allow fuel to flow to the float bowl

By Jove, a capitol idea old shoe, jolly good! Tea and crumpets all round!...............Now being's how I ain't done got no Brit in me, ah'll jez say dat's really a smart stepper by dem GY6-making' folk.................... Seriously, I ran dirt bikes all my life, and never heard of that before. I can think of an aftermarket tank on my first Yamaha, and OEM tank on my first thumper Kawasaki, that both could have used a flow stop like that screwed into the petcock fitting. When you've been pitched headfirst and shoulders-deep into a berm, you're not thinking about keeping spilt fuel off of that hot exhaust. A gas fire nearly burnt Jerry's Kawasaki to the ground. Lessons learned.

 

[ezcome-ezgo]

By Jove, a capitol idea old shoe, jolly good! Tea and crumpets all round!...............Now being's how I ain't done got no Brit in me, ah'll jez say dat's really a smart stepper by dem GY6-making' folk.................... Seriously, I ran dirt bikes all my life, and never heard of that before. I can think of an aftermarket tank on my first Yamaha, and OEM tank on my first thumper Kawasaki, that both could have used a flow stop like that screwed into the petcock fitting. When you've been pitched headfirst and shoulders-deep into a berm, you're not thinking about keeping spilt fuel off of that hot exhaust. A gas fire nearly burnt Jerry's Kawasaki to the ground. Lessons learned.

It's called petrol, Chap.

 

[Denny]

Yes a manual valve should work provided you use it!

 

[Snaker]

Those things aren't required but are/can be a nice feature.

There is something of a fad in the scooter world to switch them out to a manual.
But the reasoning is a bit grey area.
They have gotten a reputation of supposedly causing a lot of run issues.
I think that there are a very small number of legit problems mixed with a lot of misdiagnosing.
I had an issue once but the petcock was fine.
What happened was the cheap Chinese vac line kinked where it routed around the carb and blocked off vac.

So, either way with the style of petcock but cap the opening for sure.

 

[Willie1]

A couple examples of vacuum operated petcocks.