TOPIC:

This might be a silly question, but I've almost got my '79 KZ400H ready to start - but where does the vacuum line coming from the petcock attach to?? The carb...? If so, where...? On my Virago it attaches to the vacuum canister, but this bike doesn't have anything like that. 

Yes, the carbs.  The parts diagram shows the hose quite clearly.

Nessism wrote:

Yes, the carbs.  The parts diagram shows the hose quite clearly.

 

Same bike, Same problem. Partzilla diagrams of carburetor, fuel tank, petcock, doesn't show the vacuum line. What parts diagram shows it?
For now, I pulled the sync plug on the left carb and attached the vacuum line there. But I'm sure thats not where it should go. At high speed I need to switch to PRI do to fuel starvation.
The PO couldn't figure it out either. He had the petcock vacuum line connected to the carb air vent port. He must of used PRI all the time.

www.partzilla.com/catalog/kawasaki/motor...0-h1/carburetor-assy

1979 KZ400-H1. Carburetor assy diagram.
#19 = vacuum tubing. #31 = fuel hose. #36 & #44 = vents. #35 & #43 = fuel overflow tubing. I guess this is correct.

 

martin_csr wrote:

www.partzilla.com/catalog/kawasaki/motor...0-h1/carburetor-assy

1979 KZ400-H1. Carburetor assy diagram.
#19 = vacuum tubing. #31 = fuel hose. #36 & #44 = vents. #35 & #43 = fuel overflow tubing. I guess this is correct.
 

OK. Thanks. I see it now. Upper front inside of the right carburetor. I think I missed it as #19 is mis-labled as "Hose, fuel inlet"

Sometimes the Kawasaki labeling is a tad confusing and inconsistent. hee. But the vacuum ports on CV carbs are typically high up on the carburetor engine side. and the vents are usually kind of mid-body and above the fuel inlets. 

ps: after seeing Nessism's post, I went to the diagrams and was like yep there it is, then saw it listed as Fuel Inlet Hose and was like wait, what?!?! ... had to stop 'n think. doh.

Problem solved That vacuum port on the carburetot was just open to the air. I connected it to the vacuum port on the petcock and now the bike is starting and idling much better. Also, I don't hear that sucking sound any more.
Dr. Frankenstein, Did this also work for you?

Well, I looked at the colored pic of the carb and sure enough there was the vacuum port snugged up underneath the right carb lid - so I took the carbs off *again* and attached it and Yes, it seems to work, but I don't have it hooked up to my petcock yet, I just have a tube coming off it; I just fired my KZ400H up for the first time today in God knows how many years (I bought it as a basket case), but my right cylinder doesn't seem to be getting gas. I have spark, but the left pipe is cold, while the right side is running fine, so I think it's not getting gas. I pulled the plug, but it didn't smell particularly gassy. I think I just have to dial it in again, it's a little sluggish on the acceleration too - any tips there? 

"That vacuum port on the carburetor was just open to the air. I connected it to the vacuum port on the petcock and now the bike is starting and idling much better." - Could that be a part of the problem...? Does it need to be attached to the petcock and pull a vacuum to run right?  I also notice the carbs are fed by that "T" joint - did I not let the carbs fill up enough?

Dr. Frankenstein wrote:

Well, I looked at the colored pic of the carb and sure enough there was the vacuum port snugged up underneath the right carb lid - so I took the carbs off *again* and attached it and Yes, it seems to work, but I don't have it hooked up to my petcock yet, I just have a tube coming off it; I just fired my KZ400H up for the first time today in God knows how many years (I bought it as a basket case), but my right cylinder doesn't seem to be getting gas. I have spark, but the left pipe is cold, while the right side is running fine, so I think it's not getting gas. I pulled the plug, but it didn't smell particularly gassy. I think I just have to dial it in again, it's a little sluggish on the acceleration too - any tips there? 

"That vacuum port on the carburetor was just open to the air. I connected it to the vacuum port on the petcock and now the bike is starting and idling much better." - Could that be a part of the problem...? Does it need to be attached to the petcock and pull a vacuum to run right?  I also notice the carbs are fed by that "T" joint - did I not let the carbs fill up enough?

Without the vacuum line hooked up to your petcock, the petcock won't open, allowing fuel to flow.  Exception being, if your petcock has a prime feature, and you are using it.  Or the petcock has completely failed, and fuel is flowing all the time regardless.

Also, the vacuum hose off the carb should never be left open.  I will cause a massive vacuum leak.  Connect it to the petcock, or plug the end if you are using a remote tank, or prime, to run the bike.  

To check if fuel is reaching both carbs, remove the drain plug on the float bowl.  Gas will pour out if the bowl is filled, so be careful.

In this instance I was using a syringe body and some fuel line to add a little fuel to the carbs - the tank is not yet on - to see if it would start, and it did, but only on the right side. Right side pipe was hot, the left was bone cold. I checked the left side for spark, and I do have spark on the left, just no fuel, or so it seems. New carb boots too. I'm thinking timing...So, what you're saying is, after I get the crankshaft seal fixed, plug the end of the vacuum hose, add fuel and try to start it...? Will it/ should it run better?  Shouldn't the fuel be distributed equally via the Tjoint when fuel enters?

All of which makes me suspect the T joint too, which would suck because I went through the carbs with brushes, carb cleaner and ultrasonic, fitted it with new diaphragms and jets and tried my best to make sure it was ultra clean - but didn't split the carbs...I will be lying awake at night thinking about this...but still, that passage is what...? A quarter inch in diameter? Seems unlikely it's clogged, 'unlikely' being the operative word here.

Incidentally, how many turns out should the pilot screw/needle be?  I currently have it set to two turns out. 

As long as the t fitting is not clogged, fuel will be distributed as needed. 

However,if the vacuum line is open to the atmosphere, the mixture will be so lean that the cylinder will not fire no matter how much fuel is in the bowl. The vacuum line must be connected to the petcock or it must be plugged.