vacuum lines

just bought my son his first bike 82 kz750h LTD canadian bike the 2 vacuum lines were not hooked up as the petcock needs to have a kit put in it. I know the 1 line goes to the petcock but not sure about the other one my best guess is it's the right lenght and size to go into the hole in the front of the airbox is this correct.

OK:>The larger line is obviously the fuel line and goes to the carbs.You might want to put in an In-line filter also.The smaller line usually goes to the port on the 2nd carb in from the left.This makes the petcock work by sending the vacuum signal to it,letting the fuel flow in the "On" position.Fuel will allways flow in the "PRI" (prime) position.The outermost carbs have a port to attach vacuum lines to the Air Injection System.The 3rd carb has the same port,but should be capped.If the Air system has been disconnected or capped,make sure ALL 3 other carb ports are plugged,and make up a new section of 3/16th vac hose to go from carb to petcock.

bikerfam wrote: just bought my son his first bike 82 kz750h LTD canadian bike the 2 vacuum lines were not hooked up as the petcock needs to have a kit put in it. I know the 1 line goes to the petcock but not sure about the other one my best guess is it's the right lenght and size to go into the hole in the front of the airbox is this correct.

Am thinking the Canadian model doesn't have the air injection apparatus.

In any event, a vacuum nipple should be plugged (capped off) unless dedicated to a specific use such as operating a vacuum petcock.

Otherwise, an "open" vacuum creates a large undesirable air leak regardless of where it exits, air box or elsewhere.

Vent lines (float bowl venting) exit to open air (routed to exit under the seat or underneath the bike), and on some models into the air box.

Good Fortune!

This pic courtesy of wiredgeorge at www.wgcarbs.com

guess i should of said 2 small hoses and one larger

thanks for the pic it has one tube from the vent tube on the second carb and one from the middle carb and the fuel line going in on the middle as it's a canadian bike it doesn't have the air suction system as the us models so i'll put one line to the petcock and just cap off the other one and try that thanks

Hi guys,

I don't mean to hijack the topic or anything, but I have a question regarding the air suction system. I have an '83 GPz550 which appears to have had some work done on it. It has no airbox, instead having 4 separate air filters, one on each carb. The two vacuum lines from the top of the cam cover have been connected to each other, is this ok? What effect will it have? There are T's between carbs 1 and 2 and between 3 and 4. These are connected to two separate lines that were dangling down beside the engine. Are these the vent lines? Should they stay unconnected, but nicely routed? What are they vent lines for? The vacuum for the petcock comes off carb 3, the others have what appear to be factory seals over the connectors.

Thanks

Archiddeon wrote: ...question regarding the air suction system...'83 GPz550...no airbox, instead having 4 separate air filters, one on each carb. The two vacuum lines from the top of the cam cover have been connected to each other, is this ok? What effect will it have? There are T's between carbs 1 and 2 and between 3 and 4. These are connected to two separate lines that were dangling down beside the engine. Are these the vent lines? Should they stay unconnected, but nicely routed? What are they vent lines for? The vacuum for the petcock comes off carb 3, the others have what appear to be factory seals over the connectors....

The two vacuum lines from the top of the cam cover have been connected to each other, is this ok? Yes.

What effect will it have? None.

There are T's between carbs 1 and 2 and between 3 and 4. These are connected to two separate lines that were dangling down beside the engine. Are these the vent lines? Yes.

Should they stay unconnected, but nicely routed? Yes.

What are they vent lines for? Float bowls.

Vent hoses should exit to open air. Some folks route the hoses over the swing arm (along with the overflow hoses) to exit underneath the bike. Others retain the stock routing to exit underneath the seat, such as shown below on KZ900.

Good Fortune!

Awesome, thanks for the quick reply, Patton :laugh:

bikerfam wrote: thanks for the pic it has one tube from the vent tube on the second carb and one from the middle carb and the fuel line going in on the middle as it's a canadian bike it doesn't have the air suction system as the us models so i'll put one line to the petcock and just cap off the other one and try that thanks

Greetings from Canada
I have an 1980 kz750E1 which is pretty much the same bike. If your carbs are stock then they are the Keihin CV34 same as mine. Like you said. fuel line goes in on the bottom between carbs 2 and 3. Vacuum line from #2 nipple to the petcock. put caps on the nipples on carbs 1, 3 and 4. Previous owner if short of a vacuum cap may have just run tubing from one carb vacuum nipple to another. Some people run an aftermarket non vacuum petcock like a Pingle. If you are doing that then just cap all vacuum nipples.
Have fun.

The engine looks mostly stock (except that the airbox is gone with each carb having it's own air filter and the lines from the tops of the cam cover being connected together), including the petcock (took it apart to clean and definitely has the vacuum seal in it).

But ... the vacuum line to the petcock is coming off the carb for the 3rd cylinder (sitting on the bike, it's 3rd from the left). It doesn't look like it's been tampered with as all three of the other carbs have very neat black plastic caps covering the vac connection. Any ideas why the change here?

The first photo is a top-down iew of all 4 carbs. As you can see, fuel enters between 2 and 3, but vac line comes off 3. The second pic is an engled shot looking in at carbs 2 and 3. See the black cap on carb 2?

(My apologies, the engine is still VERY dirty. If it looks very open in there it's because I took the wiring harness off yesterday for cleaning and repair).

It doesn't matter which vacuum nipple is used to supply vacuum through a tube to the petcock, as any of the vacuum nipples may be dedicated to such purpose.

Some 4-carb sets are designed with a 5th vacuum nipple for the petcock. But even then, any vacuum nipple may be selected.

Any unused vacuum nipple should be capped (plugged).

Good Fortune!