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'83 KZ550 starts but dies after 5 mins 20 May 2017 10:45 #762297

  • NDSpectre
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1983 Kawasaki Spectre KZ550 - 1400 original miles - have owed the bike for 30 years. Put in a new head gasket after I cooked the original one when I overheated the bike while trying to fix a high idle condition about 3 weeks ago - now good compression in all cylinders again - 150 psi cold engine. Also installed 4 new float bowl seals on the carbs due to a leak issue with carb #2. Plugs are newish NGK that are clean and have the correct gap. Original airbox with new air filter. Bike starts and will run for about 5 minutes and then the idle starts to drop (can save it sometimes by opening the choke a little) then for the second time in a week the bike will just die and not restart. Only other symptom is that exhaust pipes 1-3 are all reading 700-800 degrees after a minute or so after starting and #4 is reading 150 degrees. Obviously the #4 cylinder is not getting enough fuel or something (spark is good). Some guy who stopped to help told me mid-80's Kawasaki's have "a fuse problem that causes them to die and later restart without a problem." I am getting to the end of my rope on this bike and am looking for a suggestion that will help it run well or I am considering either selling it or parting the damn thing out.

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'83 KZ550 starts but dies after 5 mins 20 May 2017 12:32 #762305

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Obviously, #4 is a problem. At 150 degrees, it's probably not firing at all. Check the plug. If it's covered in gas, then you have a stuck float or missing jet or the choke plunger is stuck open. If the plug is dry then you probably have a plugged pilot or intermediate jet.

I don't recall if the TK26 CV on the spectre has the rubber plugs over the pilot circuit or not (the TK26 on the H models does have them), but if it is supposed to, and the plug is missing, then you would be getting too much fuel into the pilot circuit. This is a common problem on the TK26 CV's and is easy to miss.

Valves out of adjustment can also cause a motor to stall out as it warms up. A bad coil or bad pickup can have the same effect, but usually will cause two cylinders to drop out.
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'83 KZ550 starts but dies after 5 mins 21 May 2017 05:46 #762367

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Here is a diagram from the maintenance manual for the '83 Spectre 550 Shaft drive carb page. I have dissassembled and checked/cleaned parts 1-6 and 14-28 in all four carbs. I have not touched parts 7-13 in any of the carbs. I sent the carbs down to TX to wiredgeorge about five years ago and got them back (also photo attached) without any of the the seal plugs (#7 on the carb page diagram). You can just look down the hole the see the pilot screw (#8) with a flat head screw on top.
One thing I will try today is to switch the coils (and spark plug wires) and see if I get the proper exhaust temp on cylinder 4. I am getting better at understanding how the carbs function, but I still do not have a good understanding how the choke operates on this setup, as it obviously does nothing to restrict the throttle plate in the throat of the carb. Can anyone explain how the choke actually works with the four carbs? Thanks - I like to work on mechanical things, but this is truly getting frustrating.
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'83 KZ550 starts but dies after 5 mins 21 May 2017 10:10 #762379

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#7 is not needed as long as the oring on the pilot screw #8 is in decent condition.
The rubber/plastic plug I was referring to covers the pilot circuit, but your TK26 carbs did not come with it according to your diagram.

The "choke", called here a "starter plunger", I believe actually just eliminates vacuum from the top of the CV slide. This prevents it from lifting, or from lifting at the same rate. This causes more fuel to get pulled since the air is now being restricted. But if the plunger #11 doesn't return all the way or doesn't seal, there will be too much fuel during normal operation. I think something similar can happen if the diaphragm has a hole in it.

Other plunger-style chokes sometimes just give an alternate path for fuel to flow. These are usually called enrichener type chokes, as they don't actually choke anything. I'm not positive what type yours is.

If your #4 plug is covered with gas, then check your plunger for proper operation. But don't get too far into that without checking some of the more basic things I mentioned... spark, compression valve adjustment etc.
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