Bonneville America Forums Forums Technical Forums General Tech Vacuum Hose... Where Does It Goes?

Hey everyone. I just bought my 2002 Bonneville America. When my mechanic inspected it he found a vacuum hose that wasn't connected on both ends (which he believed should have been). Its the hose coming off the left cylinder's intake manifold. Does anyone know where this hose is supposed to go?

Here's a link to a photo of the hose in question.

http://www.flickr.com/photos/63141480@N06/5741248503/in/photostream

Kris

That should just be blocked off if the air injection system has been removed. It runs the pump that injects air into the exhaust port. If you have tubes going into the head next to your spark plugs that lead up under the gas tank and connect to a vacuum pot that vacuum line should also connect there to make it operate. Most remove the tubes by the plugs and put a block off plug in there then remove the vacuum pot under the gas tank and that vacuum line gets removed and blocked. There is also a larger tube that goes to the air box on that side.

I doubt the previous owner modified the bike much. Is that tube meant to connect here?

http://www.flickr.com/photos/63141480@N06/5741325783/in/photostream

Also what is the purpose of disconnecting those lines?

Kris

Yes that is the air injection pump. It causes the exhaust headers to blue quickly. Should be a large tube from that pump to the air box and one to each side into the head next to the spark plug.

Just out of curiosity, aside from discoloration of the pipes, what is the purpose of that system? The bike runs fine with that tube disconnected. I'm curious what it does and why people remove it.

Should I reconnect it until I make the decision to remove that system?

That main thing is that you don't have a vacuum leak, if that line was just open it should not have been running right. That tube next to the spark plugs make them difficult to get out. The purpose is to help lower emissions so it passes US EPA standards.

As Ian stated, it is for emissions control purposes. It does not effect performance either way. That said, mine is off & capped.

So should I reconnect it to that spot for now? I'm going to take it in to South Bay Triumph soon for a full tuneup, but I need to ride it as is for a few weeks. Strange that the bike runs fine without it, it pops a little when decelerating, but that's probably just the aftermarket pipes.

If you are not going to remove it just hook it back up for now. Mine is also removed and plugged.

Get rid of the Air Injection System. You can buy kits from NewSpeedmaster or Fast Eddy to do it, complete with instuctions. It's pretty easy to do.

But save the vacuum hose, as I recently found out, it can come in handy for other purposes on your bike.

Ian can confirm, but as I recall, popping on decel indicate you are running too lean. If you have after market pipes, you should re-jet the carbs. While you're at it, open up the air intake, it's easy enough to do. Get rid of the "snorkel" that restricts the airflow and put in a Unifilter. Let your engine breathe, she will thank you for it.

excessive popping on decel is usually a lean condition, yes. You do want some or you are probably rich. This is with less restrictive pipes. Popping or backfire can also indicate an exhaust leak and the air injection causes it to a certain extent too in my opinion.