KZ400 Idle issues. I'm stumped.

What are the measurements of the boots?
Steve

Are these items listed at Z1E the correct holders?
www.z1enterprises.com/ItemDetails.aspx?i...00&item=16065-1002x2
Good Fortune!

Those are the carb holders i bought and filed out to fit this bike. I was talking about the boots from the airbox to the carb. they are really hard, and considering i replaced the intake boots, they are presumably the last place an air leak could occur. I will measure them when i get the carbs off the bike. I got some OEM pilot jets for this thing so i'm gonna take the carbs off again, put those in there, fiddle with the timing some more and see where i'm at. I thought about setting the timing with a tester light, because if the points are just closing when the crank is positioned at the "F" the light should flicker, or be on. I'm not sure the ohm method is working for me here.

If they're leaking a bit, it shouldn't cause running problems. If you can't find some boots, you can make some out of radiator hose or silicon.
Steve

The K and L pilots were slightly different than the OEM pilots. the holes up the tube were a tad larger on the factory jets. I put those OEM pilots in, synced the carbs, idle issue remained. I completely disassembled the advancer, cleaned it really well, lubed it up, set the timing using a multi meter EXACTLY as per the manual (its really not that hard). I check the timing with a light and it was still slightly off. With the engine running and shining the light on the advancer mark i loosened the plate screws and slowly turned it until the timing marks were alining perfectly, and the idle dropped. WTH?

The bike now runs as good as it ever has with the idle issue seemingly gone, although i haven't ridden it much. after a short 10 minute ride i pulled the plugs and the #2 cylinder is still rich while #1 looks perfect. I pulled the carbs off again, and meticulously compared the jets and housings. everything appears to be identical. has my spark plug cap/wire gone bad? Im still baffled by the timing as well. Could it be that the cam chain has stretched out and is no longer giving a reliable time? the bike still feels boggy in the middle/upper of the RPM range. starting at about 5500.

The good news is i have become a pro at getting the carbs on/off this bike. :ohmy:

I called up Z1E today and it was suggested that the needle jet holder could be worn. I pulled them out and the one on the carb that was running rich does appear to be slightly ovaled. Holy crap, could this be it!? This would explain the bogging at 1/4-3/4 throttle. There was a used set of them on ebay so i bought those, hopefully they aren't worn as well. I checked the sparkplug wires and they are within spec. The caps would read so i replaced those as well. if it isn't these needle jet holders i don't know what to do.

You may swap the needle jet holders between carbs and see if the rich condition follows the presumed worn out part.

New plug caps in. The used jet needle holders i got off ebay are in much better condition than the existing ones. swapped those out. Set the timing again and synced the carbs. Its still running rich in #2 and the erratic idle is back.... I dont know what to do. here is a list of everything i fixed/checked

adjusted valves,
cleaned and lubed advancer.
set point gap
set timing
new battery
cleaned carbs THROUGHLY
carbs completely rebuilt, with OEM pilot jets
new diapraghms in carbs
replaced jet needle holders with used good condition ones off ebay
carb floats set with tube
carbs synced
replaced carb holders
Air box boots are hard but appear to be in OK condition, doesn't seem to be any leaks.
New OEM air filter
compression is good 150PSI on both
tested spark plug wires - good
new spark plug caps
new spark plugs
stock exhaust with new gaskets, no leaks.

Don't know if you already have the matching service manual for your bike, Vic. In case you don't you may download the carburetor section through this link:
www.kz400.com/Workshop%20manual%20bilder...nual%20p.150-155.pdf

Something is obviously still wrong in the rich running carb. Makes no sense though that you are able to get a blue flame through the Colortune on both carbs. I suggest you clean the plugs from carbon and test again.
Check out thoroughly that everything is there as described in the manual, jet sizes, o'rings, etc (with special attention to the o'ring and washer behind the spring in the pilot screw). and adjusted to factory specs.

Hmmm, i will try the colortune tomorrow to see whats going on, i haven't used it since i really went through this thing. I bought the pilot needle washer and o ring brand new from kawasaki, and they are in there. is it possible the spark plug is not seating deep enough on that side? I read that that can cause carbon build up. The plugs look great when i just let it idle for 10 min with a fan in front of it. Only once its been ridden does #2 get sooty. i suspect the slight hesitation i feel in the mid range is a symptom of the rich condition in #2

Is it possible the needle is not seating right in the holder? i guess i will switch them and see what happens. It still doesn't explain the erratic idle. Im tempted to buy a used advancer off ebay and new points/condenser so i can rule that out. There is something strange going on there. Could my cam chain be stretched out? I adjusted the tensioner and there doest seem to be any particularly tight/loose spot.

DoctoRot wrote: New plug caps in . . . tested spark plug wires - good
new spark plug caps. . . .

Presupposing a perfect air/fuel mixture into each combustion chamber, incomplete combustion may result from weak spark due to excessive resistance in the secondary loop.

How were the plug wires tested?
An ohm-check isn't an adequate test, and won't show leakage of high tension voltage through old hard, cracked, worn-out insulation on the wires.

Are plug wires solid core or suppression core?

What spark plugs are fitted?
Am thinking that spark plugs for the model at hand are supposed to be NGKB7ES.
And NOT "R" plugs such as NGKBR7ES.

The caps are likely resistor style caps, having built-in resistance.

If there's going to be any resistance at all in the secondary loop, it's important that resistance be in only one component, such as resistor style caps OR "R" plugs OR suppression core plug wires.

Resistance in more than one secondary loop component results in weak spark and incomplete combustion.

Could install new Dyna solid core plug wires (they come with caps already built-in) and new NGKB7ES spark plugs.

Dyna solid core plug wires are available from Z1E:
Click here > Black
Click here > Red





Good Fortune!

Glad to know to joined the forum Z650Spirit! I am sure you will share all your knowledge with this great community.
Best regards from Buenos Aires.