Running Only in RES

modest911 wrote:

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What vacuum line and varb nipples are you talking about -
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Many kz petcocks are vacuum activated. A vacuum activated petcock will have two brass spigots on it. On one you will have the rubber fuel line attached and this will lead down between the carbs. It may go straight to a T junction between carbs 2 & 3 or it may go to a T first and then each of two lines go to Ts between carbs 1& 2 and 3& 4. The second spigot on the petcock will be a slightly smaller diameter and from this a short rubber tube will connect with a brass nipple on usually the #2 carb. When the engine fires or turns over some vacuuum is created in this tube and it pulls rubber diaphragm in the petcock and allows fuel to flow. If you have a vacuum type petcock and you dont have this tube hooked up properly then fuel wont flow right. Hope this helps.
Good luck.
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Woodstock ON Canada
1980 kz750E1, 4->1, K&N pods

Post edited by: jr, at: 2006/03/08 17:23

Fuel will flow in the res setting on a vacuum petcock, whether or not you have vacuum, so I'd start with the petcock. Sounds like you might have a vacuum leak that's causing several issues. It sounds like you have several other things that are causing problems so I'd take them one at a time.

Backfiring can be caused by vacuum leaks, and often it seems like the anti smog stuff, especially on older bikes, ends up full of leaks, causing backfiring. Even my 95 had serious leaks in the anti smog hoses. I removed and capped them.

Each of your carbs should have a vacuum nipple on the manifold where it connects to the engine, used for syncing them. Each of these nipples should have a rubber cap over them, except for the one that has a (should have) a hose connecting to the petcock.

Air leaks are BAD and can cause serious damage. You'll want to get this stuff right before moving on to other things.

fergyfer wrote:

Fuel will flow in the res setting on a vacuum petcock, whether or not you have vacuum,........................
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Never knew that.
Thanks
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Woodstock ON Canada
1980kz750E1, 4->1, K&N pods

BARNEYHYPHEN - No problem - I was just so ready to ride and didnt go anywhere I hope you understand -


JR - I think you might be on to something - I do have the vacuum type petcock - Also I cleaned it out today - It was pretty clean - But the question is now - I cleaned out the carbs over winter and I think I might have put one of the fuel lines coming from the petcock in the wrong place -


In between carbs 1&2 i have the T joint you are talking about and also between carbs 3&4 I have the samething - But in the same spots I have two other nipples which I thought to be some soft of over flow (besides what is on the bottom of the carbs) - So when I put the carbs back in the bike I put the fuel lines back on the T's in between the carbs - But you say (if I understand you correctly) one line should of went to a smaller sized nipple - correct -

One top of that after I took out the petcock and cleaned it put it back together/put gas tank on/turned petcock to ON - no gas went down to carbs on the left (if your sitting on the bike) and I got a huge/loud back fire (my neighbors proabaly hate me - haha) -

So I think I have my lines possibly mixed up if I understood your post correctly -

This is a pictures

Post edited by: modest911, at: 2006/03/08 19:52


The red lines is where I have the fuel lines connected to - the yellow lines I have nothing connected to

Post edited by: modest911, at: 2006/03/08 19:53

Modest911
Unfortunateky I'm not familiar with your carbs. Mine are Keihin CV34s. Maybe someone else can jump in here. Alternatively you could try a search here or in the archives. I have seen pics posted showing where to connect fuel lines and vacuum line and which nipples should be capped and which are vents which chould be open. I'm reluctant to say any more and send you on a wild goose chase.

Anybody else out there ?????????????

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Woodstock ON Canada
1980 kz750E1, 4->1, K&N Pods

I hesitate to get involved since there has been so much advice given already. I hate to just add to the confusion. I know you are hot to jump on the bike and ride Modest911 and don't want you to get mad but it sounds like you had best do some basic tune up and maintenance before riding.


1 - there is a knob coming from in between my carbs - Is this a air adjustment or idle fuel adjustment

This is the idle adjustment knob and it neither adjusts air or idle fuel mixture directly. I suggest you buy a Clymers manual and read how to adjust this knob. It essentially opens the slides and allows in more airflow at idle so in a sense, it could be considered and air adjustment device. Not knowing this is the idle knob tells me it would be a great idea to have you read the Clymers to get a basic sense of the bike's functions.

2 - I replaced the fuel line going from the petcock to the inline fuel filter due to a kink

OK... won't make any obsolete band jokes for fear of getting put in the corner with Barney!

3 - My plugs are fouling - new plugs - have not even rode the bike with new plugs - Plugs smell very gassy and are black

This is likely an electrical issue and not carburetor related. Go to the Filebase and look for the MOST POPULAR DOWNLOAD. Also, you didn't mention which type of spark plug and what heat range you are using. Using the correct plug is critical. I recommend NGK plugs in the heat range recommended by your Clymer manual.

4 - I am starting to back fire - But I think that is because my battery needs charging (bad)

This could be but it is more likely due to the electrical problem alluded to in question #3. Check the battery fluid level per your Clymers manual as well if the bike has been sitting and follow their recommendations for charging using a slow trickle charger.

One last point, you didn't mention which specific 1980 model you have. If it is a vacuum actuated petcock, ensure it is not in PRIME (PRI) and is actually in RES. If it only runs in reserve, it is probably best to just replace the petcock with an aftermarket petcock as your current one is defective. You will need to describe how your current petcock fits in your tank in order for specific tips on replacement can be made.

Post edited by: wiredgeorge, at: 2006/03/09 09:44

JR, my mistake! I meant that fuel will flow in the PRI setting even without vacuum. I swear, I'm suffering from crs. I believe that RES needs vacuum to allow fuel flow. If you are free flowing in RES, but get nothing in ON, it sounds like someone has been into the petcock and put it back together wrong, or I'm just confused as usual. :blush:

With my picture above due I have my fuel lines from the petcock hooked up correctly - I have a KZ100 LTD

I use the NGK recommended plugs

An easy test to see if you've got the vacuum line to the petcock properly connected is to take the line off of the petcock and hold your finger over it while the bike is running. If you feel suction, it's the vacuum line. If not, it's probably an overflow line, and you've gotten the lines mixed up!

There should be a port on your carbs providing some sort of vacuum when the bike is running. If this port is open to the air instead of being capped off or running to the petcock, you can burn a piston easily. Please (please please!) do yourself a favor and make sure to identify the vacuum port manually before putting the rubber to the pavement.

As far as the rest of the problem goes... Keep in mind that the bike is composed of a few related systems. You're having trouble with fuel delivery and electrical, which come together inside the combustion chamber at the spark plugs. The problem with diagnosing an entire system is that one bad component in a system (such as the battery in the electrical system) can make other parts of the system work less effectively.

I've wasted a lot of money by being impatient. If you suspect the battery, start there and find out how it's doing. Then move on from there. The worst feeling is to find out that you've replaced something rather than testing it first to make sure that it's actually bad.

Good luck, and keep us updated!

Modest911, I know that feeling, mine's in many pieces right now. Hope you get this thing sorted soon.

WG, I'm only 6'3"/223, so there's more than enough room for both of us in my corner. Be bold, go out on a limb with the attempted humor.

OKay so I know I have my fuel lines going to the correct place - But I have one more question for now - When you turn the gas on is it suppose to flow out of the petcock and in the carbs?

The reason I am asking is because the right side of the petcock does this straight down to the carb - But the left side does not. I did end up cleaning the petcock by the way