vacuum system. PLEASE HELP!!

I have an 82 kz750, i have found alot of info on this topic except I still am unclear on some things. I removed the emissions deal because it was annoying. I ran a hose between each reed valve deal. I was then informed that you must plug the vacuum holes on the carbs. I just cut up the tube into sections and screwed a bolt into one end for use as plugs. But the petcock is vacuum operated also. Does this need to be plugged? Do you need to run it on prime? I took my bike for a spin yesterday(finally got above freezing, about 40 degrees). Didnt seem to run like before. Even after warmed up, throttle was slow to react, and after letting off the throttle it stayed at that rpm for quite a while, and never did resume idle. Could this be because I didnt plug the carb ports 100%? Before I put the plugs on, I could blow in them and some air escaped but not alot. Also, could I just run a line from the carb to the petcock? Which carb needs to be run to the petcock, and is the emission system necessary to run the petcock?

I'm not that familier with CV carbs. I assume that is what you have, but it should work basically the same way as the slide carbs. The slide carbs have 4 rubber manifolds between the carbs and the head, each one with a vacuum fitting. All 4 are plugged with a rubber cap on non emissions models. (pre 1979). In 1979-up they still had 4 vacuum fittings, the 2 outer are capped, the 2 inner have rubber hose to the emissions valve or whatever it's called. If the valve is removed simply cap the vacuum ports just like it was done factory previously. The vacuum petcock should be operated completely independent by it's own vacuum port right on one of the carb bodies, but if not that way, you can run vacuum line to any of the 4 fittings on any of the 4 rubber manifolds and it will work just fine. The main thing is the vacuum ports are either used or plugged so no air leaks.

You need to use a smooth bolt shank to plug the hoses. The threads of a screw will allow a vacuum leak unless you turn the screw all the way in to the head to seal the tube. There should have been two vac hoses to the carb-holders, but not to the carbs themselves. Those two carb-holder ports should now get capped to match the other carb-holder ports. (The outer ports may point downward while the inner ones point upward.) Your symptoms sound a little like a vacuum leak.

Like Ron said, I thought the hose for the vacuum petcock was seperate from the emission stuff. The emission stuff is not needed to run the vacuum petcock. I thought one carb had a dedicated port for the vacuum petcock, but I can't say for sure on your bike. I think the later bikes may have used one of the carb-holder ports for the vacuum on the petcock.

A photo might help us spot it. Look at the #4 carb (the one all the way to the right). On the left side of the body is there a port sticking out near the engine side of the carb? That's where my 550's get their petcock vacuum.

Post edited by: loudhvx, at: 2008/02/27 23:18

yes, carb 4 is sticking out the engine side of the carb. Except I believe that carb 2 runs the vacuum petcock. I will get them capped better somehow and see from there. Thanx

Sorry about that. I think you're right. I forgot I actually have a 750 manual for 80-81. That shows the carbs each having a port built into the carb body near the engine side. From the photos it looks like #2 ran the petcock. #1 and #4 ran the air suction system control valve, and #3 was capped off. The carb holders don't show any ports. I guess Kaw deleted them and moved them to the carb bodies.

By the way, what model do you have? My manual covers E, H, and L.

I used blown fuses to plug the vacuum lines (except for #2, which runs the petcock, of course). I tried some purpose made vacuum plugs I got at an auto parts store, but they never did last very long before they cracked and started leaking (apparently, the rubber used to make them doesn't much like sunlight or gas fumes or heat).

Jordan,

From the factory, the two outside carburetor vacuum fittings (carburetors #1 and #4 - where #1 is the far left when sitting on bike) typically will have hoses connected and joined with a tee fitting. This tee is then be connected to your vacuum switch which in turn connects to fittings on the valve cover. That's the system you just removed. The #2 carburetor vacuum fitting should be connected to your vacuum actuated petcock fitting located on the left underside of the gas tank. The #3 carburetor vacuum fitting is capped. So in short, you need to run a hose from the vacuum fitting on #2 carb to your petcock. So the vacuum fittings on #1, #3, and #4 carbs must be capped. I don't know where you live, but if you have an AutoZone store or similar, go buy a set of generic 7/32" vacuum caps (there are 6 in a pack for a couple of dollars) - they fit perfect on the CV carbs.

Hope this helps...

I found the same thing. The store bought caps last about a week. A month if you're lucky.

Hmmm, I bought the AutoZone caps a year-and-a-half ago for both my bikes (Mikuni 32's and 34's), and they've been fine. I believe WiredGeorge also uses the same and has never had a problem. Might very well be a brand problem, though.

Obviously there's nothing wrong with using pieces of hose plugged with shanked bolts, but I would use a sealant together with the bolts. I opted for the caps simply because it also looks neater in my own anal opinion...

Bottom line is whatever method you use, make sure it's air tight, and the vacuum fittings on #1, #3, and #4 carbs are the ones that should be capped when the emission system is removed.

These vacuum plugs from Z1E have performed well for me.

Z1E's VacPlugs

Norseman wrote:

Hmmm, I bought the AutoZone caps a year-and-a-half ago for both my bikes (Mikuni 32's and 34's), and they've been fine.

I'm pretty sure I got mine at Murray's or Autozone. Theyare the "HELP" brand. Mine looked ok at first glance, but squeezing them showed the cracks. After several more months they would start to crack anywhere they were stretched.

Went to advance auto parts tonight and boughut vacu-tite vacuum plugs. Fit nice and tight. Started right up and idled much better. Gonna give it a shot again in the morning and see the difference. Thanks again for all the help