ZL900 Fuel tanks (return lines)

[ARCHIVE_tagedieb]

Can not keep it running.

I left my '87 zl600 in a friends storage shed for 4 months. Before storing it, it ran quite well, considering all the wear and tear. Good idle, clean plugs, smooth power, clean exhaust.
That was before.
After getting it out of the shed, it wouldn't fire. Gas smelled slightly varnished, so i drained it, put in fresh gas, fuel treatment. Pulled the carbs and spread healthy amounts of carb cleaner through all passages, rinsed out float bowl area. They seemed pretty clean when I had them apart. I've cleaned these carbs before. I didn't make/change any adjustments on the carbs other than idle screw. Idle mixtures are stll factory-sealed, syncronization has never been touched. Vacuum ports are all capped. Gas flows via "prime".
I filed the old spark plugs with some sandpaper and cleaned them a bit with propane.
Snipped the tips off the spark plug wires, only some were blue-green crusty.
Tested the plug boots at 5K ohms. Boots and wires are a couple years old.
Throws a mean spark from the plug wire. Spark with the plug boot attached is far less impressive. Same for all four.

It's extremely hard to start. Have to choke and flood it like mad. Only way to keep it running is at 3K rpm with full choke. Fires on all 4 like this, pretty smooth despite the heavy choke. Bring it below that, or try to reduce the choke causes it to start misfiring, and starts to backfire through the carburator.

I don't think it has a vacuum leak. Ports are all plugged, and I've never had trouble with the carb-to-head boots. The carbs are bare on the airbox side - no boots or anything.

What is going on? I'm out of ideas. Please help.

 

[ARCHIVE_kawasaki-krazy]

Sorry to say this but it really does sound like a serious air leak between the carbs and the head. I would re-check all the rubbers and make sure.

Hope this helps

KK

 

[ARCHIVE_zlMark]

try spraying a little WD40 around to check for vacuum leaks. Try adding a 50/50 mixture of seafoam and gasoline add it while engine is hot let it run for a while, until you know it has reached the carbs and then let it soak in overnight. Drain carbs and remaining fuel replace with fresh gas.

If that does not work rip out carbs and do a thorough cleaning and pull them pilot screws out!

 

[ARCHIVE_doode]

id check all the intake boots&see if thier not cracked or perished&clean faces&reseal,,3bond white?.....

 

[ARCHIVE_tagedieb]

Day 3 Update.
I've spent the past 3 days working on this. Not that I'd expect anyone to believe me, but both my friend and I are decent mechanics and this has us both stumped.
You guys were right, there was an air leak between the carbs and head. Put some new clamps on, which reduced it to a very minor air leak. It's still shows up a little with carb cleaner sprayed on it, but it's just not drastic enought to account for the behavior.
I cleaned the carb for the second time today. First time was a quick flush in my friend's driveway. Second time was 3+ hours on my porch, being meticulus. Didn't find anything that looked like a potential blockage.
We've ruled out ignition for now. It fires clean and even when it is getting the right mixture. BUT..
It will only idle. Runs fairly well and even at idle. Clean, not rich, etc. As if everything was ok.
The second I touch the throttle it dies. Rev it up using the choke, try to keep it up with the throttle - dies.
After so many checks and attempts, we're sure the idle circuit is behaving correctly. Same goes for the choke.
Problem is those primaries. If the idle screw is backed out nearly shut, it idles fine. Try and open the butterflies with the idle screw just a bit, it begins to stutter, bit more and it dies. It's as if the primaries aren't feeding any fuel. There's a drastic difference between idle and throttle.
We've been doing most of the troubleshooting with the airbox off, nothing past the carbs.
Here's the ticket: If we take a piece of cardboard and cover the carb inlets 90% of the way, the throttle works pretty well - snap the throttle and the response is pretty good, no more killing it.
I've been watching the slide piston as we troubleshoot. Sits all the way down at idle, cracking the throttle brings it up a few mm, heavy vibration, doesn't seem to move smoothly.
Can anyone tell me normal operating behavior for the slide piston in the carb? Under what conditions and how does it move?

Thanks in advance guys.

 

[ARCHIVE_doode]

is it getting a good fuel supply?......fuel line filter clean?....tap ok?........



and is the choke shutting off ok?......

 

[ARCHIVE_kawasaki-krazy]

Here's the ticket: If we take a piece of cardboard and cover the carb inlets 90% of the way, the throttle works pretty well - snap the throttle and the response is pretty good, no more killing it.

Which seems to prove that its getting its air from somewhere else.

With what you say about the sliders I would have a close look at the diaphragms next, to make sure that they are in good condition and seated correctly. I would have expected that when you crack the thottle open, the sliders should rise straight to the top and not rattle about, a few mm from the bottom.

Also there are a couple of small pipes and diaphragms on the sides of 1 & 3 carbs (coasting enricher system )which are related to the vacuum somehow (I can't quite remember just now. Someone will be along in a moment to put me right) (Rocket, Snake ..............HELP) Might be worth a quick check on these too.

I might be speaking b*ll*cks about the last bit 'cos I think that maybe only for the ZL1000. My daughters ZL400 only has some connecting pipes between 1& 4 and 2 & 3. If so, ignore me

Hope this helps

Keep us updated.

 

[ARCHIVE_Rocket]

How about the vacuum tubes on top of the carb discharge???

These are normally blocked off with a rubber caps and these caps may be cracked/leaking.

The diaphrams on two of the carbs with hoses running to the other two are for fuel enrichers. When my diaphram rubber perforated the bike didn't like to cruise, idle and accelerate where OK. Mine's a ZL1K though so these may not apply to your ZL0.6K

 

[ARCHIVE_tagedieb]

The vacuum ports above the carb discharge are fine. I've alternated between rubber plugs and crossover vaccum tubing between the carbs. All were closely inspected.

The slide piston diaphragms are also in good condition.

I don't have a coasting enriching system on my '87 zl600, but I do know what you're talking about. It goes by different names depending on the manufacturer. If I remember correctly, there's a momentary lean condition in the exhaust when the throttle closes (coasting). The CES injects a burst of gas at this point to prevent backfiring. I could be wrong.

I'm reading over both manuals now. Thanks for the good advice guys.

 

[ARCHIVE_zlMark]

vapor lock? check your tank vent or try leaving cap open while running

 

[ARCHIVE_rammy1500]

I remember my poor ole Camaro when it started cutting out and wouldn't run right, replaced the fuel pump, spark plugs, rebuilt the carb, egr valve everything I could think of but the problem was that the cat was plugged. I know that these bikes don't have a cat, but wonder if some critters packed a nice home away in the exhaust? You would think you could smell the stuffing burning but never hurts to check.

 

[ARCHIVE_tagedieb]

All great advice, thanks very much. I'm going to give it a try this Saturday. Will keep you posted with my progress (hoping I actually make some ).

 

[Pharaoh]

Hey there, Since we were talking about tanks earlier, and the possible swaps, maybe you can help me figure this:

We've got an 85' ZL900, which we're restoring. (some moron painted it turquoise, and we're putting it back to it's original beautiful luminous Red) Well the old tank has a good sized dent (you know where) - and we found a NOS elim tank that was sitting on a shelf in a back room, perfect condition, even the right red color except.... Well turns out our bike has California Emmission, which means the Fuel comes from the canister into a Fuel/Air Separator, then into TWO fuel return tubes into the fuel tank. Well the new tank only has ONE return line, so my question is, How should we hook this up, should we just put a "T" in and connect both lines from the Separator into the one fuel return tube? Would that be okay, or a BAD idea.?

Any Help is apprieciated. Thanks!

Pharaoh

I can supply picts if needed.

 

[zl900_moab]

They are just pressure vent tubes, so you can run them to a "T" no problem, I took all of the emissions stuff off of mine, and I just have them vent to the atmosphere...Good luck and I hope ths helps...
moab...

 

[Pharaoh]

ZL900 Tank

You just took off all the emissions eh? Did that affect your mileage much? I would be interrested in seeing some puctures of how your hoses are routed. The Red & blue circuits...

Pharaoh.

 

[zlMark]

Me too!

BTW

Welcome Pharoah!


My carb vents run up to the frame clamps and vent there. Tank vent runs down behind battery by swingarm vents there. Capped off vacuum to air suction valve. Removed airsuction valve assembly except for the 2 hoses, tee and rubber cap. Plugged hole in airbox with a nice shiny nickel

did i leave anything out?

 

[zl900_moab]

I am still tuning, but my mileage changed due more to the stage 3 jet kit and the SuperTrapp exhaust, I have NO vacuum lines on my bike, I manually open the petcock when I am ready to run, I removed ALL emission stuff and it did not affect rideability, and took some weight off the bike too, I used rubber corks for the air return tubes to the valve cover and the whole thing works well....When I get my carbs running right, I will post up mileage....But I did take a run the other day and got about 32 mpg....And I am running rich.
moab...
ps....Mark....You talked me through ripping out my vacuum lines, so don't play dumb!

 

[zlMark]

I wouldn't do such a thing, these types of modifications would prohibit use of the motor vehicle on the street :nonono: :nonono:

 

[Southernstyle]

Really?! OOPS!
Later,
SS

 

[Justin Lawrence]

Hi all

I have been restoreing my 87 zl1000 and have come to fitting the fuel lines and have a small metal pipe at the rear underside of the tank dose anyone know where this goes to