1981 KZ550 D1 GPZ550 won't start

If the carb holders are old, hard and have visible cracks, they are likely leaking.

Did you remove the idle mixture screws when you cleaned the carbs? If not, that part of the pilot circuit may still be clogged. Also, there is an o-ring around each of those adjustment screws. If they are hard, cracked or missing, air can leak past the screw, causing the mixture to be lean. As has been written here many times, there are no shortcuts when it comes to carbs.
 

Thanks TexasKZ, I'm a slow learner. I'll check all these things.

Have the carbs been jetting for pod filters?  If not, you have to do so.

BTW, it's normal for these bikes to require choke until the engine is warm.  

I think we're all advising the same advice 1. Full carb tear down. 2. Takes lots of pictures 3. Complete cleaning 4. New carb boots. I didn't watch the video but while you GPz is running you can spray carb cleaner where the intake boots are attached to the cylinder head. An air leak would be indicated by a drop in engine rpm. This GPz model does not have an o-ring between the intake boot and cylinder head.

The factory painted the carb bodies black. The fact your carbs are bare just indicates the PO had removed the carbs for leak repair, rejetting, etc.    

Thanks all for your comments. I'll ask a few more probably dumb questions if you don't mind. The bike now starts and runs but dies when the (full) choke is touched. In other words, when I try to turn the choke off or even slight off, it stalls. I understand in this case pilot jets may be plugged, which would make sense to me if it was one carburetor, but it seems to me unlikely that all 4 have plugged pilot jets. I did clean the pilot jet passages last week.

Another probability I understand is air leaking between the carbs and engine intake, a poor seal in those plastic 'boots' which I understand can't be old/cracked. That's a possibility, I am going to try the suggestion from srsupertrap to check this.

Someone else said change the O-rings I think in the main jets? How important is this? This engine was rebuilt about 3 years ago by a guy who knew what he was doing, I have full pictures, and it was running OK earlier this spring before it just stopped starting (suddenly). A fuse had blown at one point in the summer, I had it towed home, left it a couple of months, and then no start. Of course the fuse was changed, and it has run since. The total miles after the rebuilt is < 300. I assume the rebuilder put in a carb kit but he's inconveniently died so can't confirm that. I see warnings about carb kits for bikes not having accurate components. Is there a good quality kit I should get and just replace all the included parts? If this involves tuning anything then I'm already over my head, I've never tuned anything and don't know where to start, but maybe I have to learn.

Cleaning the carbs - I removed the float bowl and cleaned everything accessible last week. Is this a dumb question or could I just soak the entire carbs in some solution for a few days? Submerge them? Or is that going to do damage? If this is possible, what solution could I use? Kerosene? Turpentine? The bottom of the carbs and float bowl look reasonably understandable with some effort, but the top of the carbs which have mechanical adjustments under the removable cover - I'm afraid to touch any of that.

Back to pods. I don't know anything about tuning multiple carbs. The tuning was seemingly OK before the starting problem. I have the original air cleaner box and filter but have lost one of the metal brackets that holds it on (I can probably make one). I understand from the rebuilder that it's much easier to tune using the original single air cleaner rather than multiple pods, but I don't want to throw another issue into the mix that I don't understand. It's probably best to get the choke situation under control then make a decision on the pods. 

Sorry if I'm ranting. My main questions - should I order a carb kit and replace everything I can, and is there any safe way to submerge/soak these carbs in an attempt to make sure they get cleaned. Meanwhile I'm going to try the suggestion about spraying carb cleaner around the engine intakes when the bike is running, I'll post again if that looks to be the source of the problem.

Thanks
Ron

Ron... You should not "need" a rebuild kit yet. At one point, some 5+ years ago, I did a write up about a carb cleaning using Pinesol, at the other now-defunct KZ650 site. Regretfully it's lost to the bit-bin... and I doubt if I'll do another write up. But this is an option, if you want to try it... I do suggest it. Pinesol breaks down fuel varnish quite well. Don't use the flavored stuff... use the plain jane stuff!

Here's a quick G-search about this, for your reading:  www.google.com/search?q=pine+sol+carb+cleaning
Feel free to ask question about this...

RonG wrote:

<snip>

Sorry if I'm ranting. My main questions - should I order a carb kit and replace everything I can, and is there any safe way to submerge/soak these carbs in an attempt to make sure they get cleaned. Meanwhile I'm going to try the suggestion about spraying carb cleaner around the engine intakes when the bike is running, I'll post again if that looks to be the source of the problem.

Thanks
Ron

 

Good info on the Pine Sol thank you, I watched the movie. I'm off to test the leakage now then maybe to get pine sol.
Ron

I fired it up today and once it got to temperature and would idle (it runs very unevenly before that point, needing a lot of throttle), I tried spraying Gumout Carb/Choke cleaner around the inlets from the carb to the engine. The Gumout can indicates this stuff is flammable. The RPM actually increases when spraying around cylinders 2 and 4. I'm not sure what that tells me, leaks I guess, in any case I'll try to get a replacement set of the carb to engine connectors. I'm looking for Pine Sol and will do a full cleaning/soak this week.

Ron

That does indeed indicate "leaks" should be significantly better with new rubbers (OEM if you can or good quality aftermarket)

Can I ask... is it 'carb holders' I'm looking for? It's not clear to me on an exploded carb view. Z1 shows these OEM 'carb holder' 16065-1014-4 but they're not cheap. And... I would have expected it was standard practice to use some type of sealant when inserting these into the cylinder casing, would that not seal most leaks?

www.z1enterprises.com/motorcycles/Kawasa...nd-fuel-systems.html

Pine Sol cleaning the carbs.... maybe this is a dumb question but is it necessary to remove all 4 carbs from the 'rack' they are on before pine-sol soaking them, which looks like pulling out the choke and throttle control rods and sliding the carbs off. I'm afraid I'm going to upset some adjustments there that may be hard to recover. Can I just remove the float bowls and soak the lower portions of the four carbs as one unit?
Ron

I don't see why not.
Be sure to rinse thoroughly and blow all passages out with compressed air / carb cleaner.

H.