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76 KZ900 19 Mar 2023 10:05 #881778

  • mvent
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Pulled carbs again, blew them out with compressed air, pilot jets clear #4 head pipe not getting hot, #3 better but not close to cylinder  1 and 2. temp at spark plugs are pretty close on all 4. Switched plug wire from 1 and 4 no change, switched out spark plugs no change, hot compression on #4 150, other 3 between 135-150. I guess this narrows it down to carburetor ? Float height same on all carbs and all getting fuel.  Ultra sonic next. Any ideas ?

76 KZ900
76 XLCH
78 KZ1000
04 FLSTFI 120 ci

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76 KZ900 19 Mar 2023 11:18 #881782

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You make a very confusing comment if I read correctly. You say the IR temps are very similar at the spark plugs, but you have extreme temp difference at the down (head) tube. This doesn’t seem possible. Is it possible you have a blockage in the down tube. Critter nest? I bought an once engine that had short 6-8 inch sections of down tubes affixed and mice had called up into the open tube and built nest in one of them.
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.

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76 KZ900 19 Mar 2023 11:46 #881783

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Mikaw funny you said that it did cross my mind but I thought between the exhaust heat and pressure it would have blown it out. 

76 KZ900
76 XLCH
78 KZ1000
04 FLSTFI 120 ci

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76 KZ900 19 Mar 2023 11:55 #881784

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Not sure what else could cause such a temp differential between the plug and the down tube. 
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.

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76 KZ900 19 Mar 2023 14:45 #881794

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Remove the bleeder tubes under the main jets and give them a clean. Compressed air is not a cleaning medium!Did you inspect and set the pilot air mixture screws to 1 1/2 - 1 3/4 turns out? A broken air mixture screws tip can made your day!Are the carbs mechanical/vaccum synced? 

 
 
 
 
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76 KZ900 19 Mar 2023 15:52 #881795

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Scirocco, all above mentioned has been done air screws are 1 1/2 turns out. Mechanically synched for now. Thanks for the suggestions. These are Z1b carbs, are pilot jets supposed to have o rings? none of these do.

76 KZ900
76 XLCH
78 KZ1000
04 FLSTFI 120 ci

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76 KZ900 19 Mar 2023 16:21 #881798

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These are air/fuel mixer screws were the tip was broken and stuck in the carb body.

 
 
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76 KZ900 19 Mar 2023 19:28 #881807

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Here this will help with item terms. There are no ORings on the pilot jet #21, non on the main jet emulsion tube/ jet holder #20, nor on the pilot air adjustment screw #23.

 
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.
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76 KZ900 20 Mar 2023 07:39 #881816

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This is a picture into exhaust port of #4 cylinder 

76 KZ900
76 XLCH
78 KZ1000
04 FLSTFI 120 ci
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Last edit: by Street Fighter LTD.

76 KZ900 20 Mar 2023 07:47 #881817

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Looks like it’s been running rich or burning some oil, but I don’t see anything “Abbynormal”. 
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.

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76 KZ900 20 Mar 2023 07:50 #881818

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Pulled carbs again, blew them out with compressed air, pilot jets clear #4 head pipe not getting hot, #3 better but not close to cylinder  1 and 2. temp at spark plugs are pretty close on all 4. Switched plug wire from 1 and 4 no change, switched out spark plugs no change, hot compression on #4 150, other 3 between 135-150. I guess this narrows it down to carburetor ? Float height same on all carbs and all getting fuel.  Ultra sonic next. Any ideas ?
Have you tried switching the actual coils ?

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76 KZ900 20 Mar 2023 13:50 #881834

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Wookie I have not, switching wires between 1 and 4 then spark plugs without change my assumption was that would eliminate any electrical problems with coils, wires and spark plugs.

76 KZ900
76 XLCH
78 KZ1000
04 FLSTFI 120 ci

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