Unsolved Problem

[Norseman]

Hi, folks. I'm hoping someone on this forum has experienced this problem and can point me in the right direction. This is occurring on my "other" bike - a 1981 Kawasaki KZ1000.

I hope I'm not offending or annoying anyone by bringing an inferior machine into this, but I can't get a straight answer anywhere else, and I am not aware of another forum that sports the consortium of experts here (and no, I'm not kissing up, you go check the other forums and report what you observe).

I bought this bike some time ago, and it sat while I focused on my son's GS650GLX. Having completed the 650, at least for now, I wanted to get the Kawa running. The setup is not good - pods with a 4/1 Supertrapp with I believe original jets. I got it running, but when I roll on the throttle, the rpm's respond quickly, but takes forever to return to idle (30 seconds, sometimes never and I have to hit the kill switch). The cable it free and smooth, the butterflies closes with the release and return of throttle, but the rpm's stay. So if I rev it up to 3,000, that's where it stays, or takes a looong time to return to idle.

I have my suspicions (air leak), but the intake boots (what those other people call "barb holders") look OK (no through and through cracks). So please forgive me for bringing up another product in the forum, but I don't know where else to go for intelligent answers. I would very much appreciate some of your insight!

Norseman

[Steve]

Don't worry about mentioning an "inferior" product around me. I rode nothing BUT Kaws from 1976 to late 2005. 8-[

Actually, you could almost think of it as a GS1000 with a different set of parts. The problems you mention sound a lot like an intake leak. The pictures at BikeBandit were a little fuzzy, but they show replacement intake boots for $17.70. I could not tell if there were any o-rings involved, though. Try to squeeze the boots if you can, to see if they are still pliable. If they are hard, there might be cracks around the edge where you can't see them, but are enough to affect the operation.

Another area to check is the slides in the carbs. Sounds like they might be going up OK, but might be sticking a bit on the way down. Clean them will with carb spray and some steel wool, and make sure the bores are clean, too.

Considering the fact that there are pods and a pipe on there, it might just be running lean altogether. If the other 'fixes' don't work, might have to try re-jetting. Here is where my expertise drops out. I have no idea what was there stock, so I can't say what should be there now. However, based on what others are reporting on their GSs, about 3-5 jet sizes richer would be in order. Before ordering new jets, though, you might try shimming the needle to raise it a bit, as the '81s had fixed heights. You can also remove the plug over the mixture screw and open that up about a turn or so. Turn it clockwise until it seats lightly, counting the turns as you go. Record the number for each carb, then turn the screws left one more turn.

Let us know how it turns out.


.

[Norseman]

Thanks!!!

Thanks, Steve, that was clear and insightful. I just did a thorough carb cleaning, but did not address the slides, which in hindsight did appear to have significant lacquer on them. The intake boots look decent, but not using o-rings, the backs that mate with the cylinder are very "indented" from the years.

So here's my course of action: 1) Clean the slides with carb cleaner and 0000 steel wool, 2) shim the needle with a small washer, and 3) open up the pilot screws currently set at 1.5 turns out with an additional one full turn to see how idle reacts.

I'm also considering trying to use thin high heat rated o-rings and re-install boots because there's nothing wrong with the boots that I can see other than the rubber mounting surfaces are indented. I am not aware of any other high heat rated solution. Z1 also sells the four boots for $50.00, so I'll see...

I will report back with the results from my 3-point plan. Thanks so much for the guidance.

Norseman

[derwood]

I experienced this with a couple of old bikes with CV carbs. I think the idle/pilot circuit is plugged. Try taking out the idle mixture screws and spraying some aerosol carburetor cleaner in there maybe blow a little air in there as well. Put the screws back in lightly seat them and back them out a couple of turns. See if that helps. You will have to adjust idle speed as well, as it will be idling too fast if this routine works.
OK, here's my $0.02 theory on the problem. I think the idle jets or whatever get plugged with fuel deposits and crap so the engine can't pull fuel through the idle circuit. To compensate the idle speed gets adjusted with the throttle plate stop screw til the bike idles on the main jet.At this point the port in the carb bore that feeds the passage to the top of the diaphragam is just starting to get exposed to venturi vacuum. While not enough of a vacuum signal is there to overcome the stichon (sic?) of the pistons and start them rising, the pistons are very sensitive and lift at the first hint of throttle application. With the increased air flow there is now enough of a vacuum signal to hold the pistons up at idle allowing more fuel to flow out of the mains and the engine idles really high. If the engine is shut off and restarted it will idle "normally" again until the throttle is cracked and away it goes again.
Carbs may still have to be removed and cleaned as well as the fuel tank if the problem continues.
I hope this makes sense to more than just me. Then again I could be right out to lunch.
dave

[chef1366]

Your not "out to lunch" cause it makes perfect sense to me. Once the slides lift from the air from the high idle they stay that way until the bike is shut down where they can drop completely. A type of loop.
I bet it's a stuck slide or two especially if it sat for awhile and you didn't clean them. You might also have build up on the throttle body where the slide slides.:shock: