TOPIC:

1984 ZN1100B1: I replaced my rubber carburetor boots (the intake manifolds), while the carbs were off. I cleaned the carbs and put them back on. Since then, the bike runs extremely bad, backfires, plugs seems to show lean (no black soot), no power whatsoever; the only way I can accelerate is rev 'er up to 4000rpm and let out the clutch slowly. It did not do this before I took the carbs off, and replaced the boots. It would seem to me to be the boots, but they only have to hold engine vacuum, how tight do they have to be? I had tightened them fairly tight, didn't want to deform the rubber too much. I sprayed starter fluid at both sides of all 4 boots while running and heard no change in engine rpm. Ok, I took the carbs back off, checked float levels (they're at where it used to run fine), checked jets and air passages, looks great, and put the old boots back on (still in fair shape, no cracks or holes) and tightened them as much as I could. It's no better. Barely runs. Are you supposed to put some kind of glue on the carb boots at the engine to seal them real good? Perhaps it's a strange coincidence, something else just happened to break, and the problem is not the boots at all. Sorry for the long post, it's driving me nuts!

I've heard of people using a gas proof gasket compound on their boots, although it shouldn't be necessary. Especially with new boots they should be soft enought to seal themselves without any "glue".

The likely problem is the carbs as you indicated that it ran fine before you took them off. How were they cleaned? Carb cleaner can destroy rubber if the o-rings and such were not removed prior to cleaning. Have you checked the pilot screw or idle air screw adjustments? Synched the carbs?

I used a high temperature gas proof gasket on my carb boots, it seemed to work well.

Thanks,

George

I have a carburetor test bike set up with the larger CV style intake manifolds and don't use any sealant but I would if I didn't remove the manifolds so much. While silicon will melt if it comes into contact with gas, you can use it for a seal between cylinder head and manifolds as the stuff doesn't really come in contact but stuff that holds up to gas would probably be better. When you reinstalled the carburetors, did you reconnect the vacuum port hoses? 1 & 4 are joined with a tee and the tee has a hose that comes off and joins with a smog gizmo. One of the vacuum ports goes to your petcock and the other will be capped. if ANY are left open to air, the bike will run like you describe.

Thanks for the useful responses to my question. You've confirmed that some do indeed use some kind of glue on the rubber carb boots. I would still like to hear if anyone successfully installed rubber boots without using any glue. Wiredgeorge, sounds like you get by ok without any glue.

In answer to the questions:

NormZ, hi. I did not use a dip to clean the carbs; I used lots of carb cleaner spray and compressed-air-in-a-can. Works pretty good. After the first cleaning, I noticed my original 1984 factory foam air cleaner was disintegrating from age, so I put in a replacement paper filter. It ran rich. After attempting to "tweak" the mixture many times by changing the float level, I've pretty much determined that I either need to put in a new factory replacement air filter, or re-jet. But it was running fairly well, but rich, with quite a bit of hesitation on acceleration. Certainly, I've adjusted the air mixture screws many times, and put the original pilot jets back in, in case the replacement ones were a problem. Carbs have been sync'd 3 times in the last 2 years; I'm leaving that alone now while I try to get the carbs working right. Sync is really only for idle, I think, unless it's way off.

After having it running almost perfectly (still rich, though), it wasn't but about 2 days until I went and filled with gas. I went to the exact station I've been using exclusively for 15 years, an Amoco. I then drove 2 miles to work, parked the bike in the hot summer sun, and when I came out, it ran really bad again. I found orange globules in the fuel bowls, which have been clean for months. So I overhauled the carbs a 2nd time and added a fuel filter. My bike, with rear downward slope on the tank, works awful with fuel filters; I've removed it until other things work right. This time, I also put on the new carb boots, and it never ran well after that. I've now taken the carbs off a 3rd time and checked the pilot jets, pilot air jets, and pilot air passages, and all are good. Mixture screws at "factory" 2.5 turns, and floats at what worked before. You'd think the problem must be the carbs, which I overhauled, or the carb boots. It runs like there's a 2-inch gash in each of the 4 boots, but if you look, they are tight and look sealed. I can feel no air movement near the boots, and like I said, in my test with starter fluid, could detect no engine rpm changes or changes in sound.

I wonder if the vacuum smog thing, and the reed valves on the exhaust ports, can cause this much problem. It is backfiring like crazy.

Georgeha, thanks. Was that a gas-proof hi-temp "gasket" you used, or hi-temp gas-proof "glue"? I'd hate to add a gasket over the rubber. Perhaps I should warm the rubber boots and then tighten them more, with a bigger socket handle. The factory boots were indented much more than my new ones were by hand tighening with an allen wrench. But the screws don't look big or strong enough to handle much more torque than a small wrench can provide. I could find no torque spec for those screws.

Wiredgeorge, thanks. Unfortunately, the mechanic that last sync'd my carbs removed the T attachment on my vacuum lines and then he plugged the freed vacuum port. Now I have 2 vacuum ports blocked with plugs, a third goes to the fuel petcock, and the fourth goes to the smog gizmo (good name for it). That seems to work fine.

I'm about to take this in to some shop; I'm very tired. I used to have so much fun riding this Kawasaki. The new-bike shops around here won't work on bikes more than 10 years old, so I've got few to chose from.

I replaced the intakes (carb holders) on my '77 KZ650C1 this past spring. The service manual did not call for any sealant or "glue" or gasket, so I used nothing. I have had no problems since. Actually, the problem you describe does not sound related to a carb holder leak. My original carb holders were leaking and the only symptom was rough idle. When the throttle is closed, the vacuum caused by the intake stroke would suck raw air between the carb holders and head causing an erradic lean idle condition. With the throttle open, this is a non-issue because the vacuum is sucking through the open carb. Let the engine idle as low as possible and spray carb cleaner where the carb holders meet the head. If they're leaking, it will kill the engine. That's how I diagnosed the problem with my original "leaky" carb holders. Ed

You mentioned that it ran rich with the replacement filter, so did you install an OEM filter, or are you running without one?

If you don't have a filter, then that would cause the symptoms you describe.

Wow, cut to the chase, 650ed, thanks for the great information in your post. I just don't see how those carb boots can be leaking that much, if at all; I think the problem is probably somewhere else, but if it's not the boots, and not the carbs, I'm getting a little sick thinking about what's next . . .

Steell - I have been running with the paper filter, and it's been running awfully rich - it's aggravated by my elevation: 6000 feet. All year I've been thinking "the bike used to run fine, it should run fine again without re-jetting", so I've been adjusting the float level to try to lean it out, but it ain't quite doing it. It's just the last month or so it finally dawned on me that the filter may be doing it. I bought an original Kawasaki foam filter and installed it, but now this problem has taken over; I can't seem to get back to where it was, running well, but rich, to see if the filter fixes it.

At this point, my suggestion is to start from the beginning and do a complete tune up. Check the timing and the coils (primary and secondary resistance), and the plug wires and caps, remove the petcock and make sure the little filter on top is not plugged, and check the valve clearance. If all that you have done to the carbs has not fixed the problem, then maybe the problem is elsewhere.

Yes, I'll start branching out to other possibilities, but the good weather is quickly drawing to an end. If I do happen upon a solution in the near term, I will certainly post it here, fyi. Thanks.

Whenever I get a new bike and need to pull the carbs I always re-seal the intakes. I use Yamabond.......clean everything real good with contact spray, dry off, then dab it on the head where the manifolds mount. Re-mount the intakes, let dry for 24hrs and your done!

Thanks for all your comments and suggestions, particular thanks to 650ed for bolstering my feeling that the problem is not the carb boots at all, and to steell for encouraging me to start checking everything else! It's been running so very bad lately that it just seemed very unlikely that it was the carbs or boots.

Today I found what is likely the actual problem. The #1 spark plug wire is completely open, no connection through it at all, even after wiggling various parts of it to try to make a connection. I removed the wire "cap" and the cap is just fine, it just can't make a connection to the metal wire inside the plug wire. Wait, it get's worse. The secondary winding of the coil that drives plugs #1 and #4 is open; I cannot get any resistance reading through it on any meter setting. I don't know - perhaps when a plug wire goes out, the coil driving it also goes out, though I've never heard of that. I had checked both coils and all plug wires about a year ago. I will probably go order some original Kawasaki coils and plug wires.

I'm going to start a new thread over in the Electrical Forum about Kawasaki vs. aftermarket plug wires and coils. From reading in that Forum, it looks like it's generally difficult to mount aftermarket coils, though one guy had good luck, and I'll have to search for that. I am wondering if it's worth the trouble.

Thanks.