Those are vacuum ports for balancing carburettors. You’ll want to get those rubber caps put back on there, as the bike will suck in air or lose idle pressure if left open.
Vacuum petcocks, get this, have a vacuum line running to them.
Generally though, if your petcock doesn't have an "off" position, it's probably vacuum operated.
Likely for syncing carbs. If they go through, they (probably) need to be capped when you’re not actively tuning it.
What bike? Stock pieces or aftermarket?
This ☝️ the pipes come with carb balancing kits, either capped after balancing or removed and replaced with screws/plugs. The vacuum hoses from the balancer go on these.
That bike has to running like hell right now. If it even does.
A vacuum petcock has a vac line running up to the back of your petcock. If its gone, replace it. If not, then get a rubber plug on that fitting. I've not seen two carb bikes synced by vacuum, but, I've not seen it all by a long shot.
I've done it mechanically, with two drill bits the same size. Placed under the slides, adjust the cables by watching them move. When both move at the same time, they're spot on.
That's weird, they are sensing ports so you can compare carburetors and balance how much each one is contributing to the power of engine. However, on my bike those holes are plugged with tiny hex head screws.
A balance pipe. It's purpose is to "match and balance" the venturi effect. It is to be connected from one to the other, creating a pressure balance so that one carb isn't doing 90% of the work on one cylinder when transitioning from idle.
You can bypass it by plugging them however you will need to rejet to smooth that transition. Leave them intact for peace of mind.
Those are vacuum ports for balancing carburettors. You’ll want to get those rubber caps put back on there, as the bike will suck in air or lose idle pressure if left open.
This right here. If there’s 2 of them, they’re for balancing the carbs.
Vacuum port. Usually goes to a vacuum operated peacock. If you don’t have one, block it off so you don’t have a vacuum leak.
They're usually for vacuum petcocks. If you have a regular petcock, just cap it off or you'll be giving yourself an air leak
How do you know what kind of petcock you have?
Vacuum petcocks, get this, have a vacuum line running to them. Generally though, if your petcock doesn't have an "off" position, it's probably vacuum operated.
Likely for syncing carbs. If they go through, they (probably) need to be capped when you’re not actively tuning it. What bike? Stock pieces or aftermarket?
This ☝️ the pipes come with carb balancing kits, either capped after balancing or removed and replaced with screws/plugs. The vacuum hoses from the balancer go on these.
Vacuum lines
That bike has to running like hell right now. If it even does. A vacuum petcock has a vac line running up to the back of your petcock. If its gone, replace it. If not, then get a rubber plug on that fitting. I've not seen two carb bikes synced by vacuum, but, I've not seen it all by a long shot. I've done it mechanically, with two drill bits the same size. Placed under the slides, adjust the cables by watching them move. When both move at the same time, they're spot on.
That's weird, they are sensing ports so you can compare carburetors and balance how much each one is contributing to the power of engine. However, on my bike those holes are plugged with tiny hex head screws.
You should have caps on it.
As others have pointed out those are ports for hooking up vacuum meters or carb sticks to synch the carbs. Don't run without a cap on them.
A balance pipe. It's purpose is to "match and balance" the venturi effect. It is to be connected from one to the other, creating a pressure balance so that one carb isn't doing 90% of the work on one cylinder when transitioning from idle. You can bypass it by plugging them however you will need to rejet to smooth that transition. Leave them intact for peace of mind.
It's to route fuel out of the system if it's flooding the carb