1985 zx900 A2 carb issues - ZX Forums
 
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post #1 of 6 (permalink) Old 07-18-2019, 04:06 PM Thread Starter
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1985 zx900 A2 carb issues

Hello, I recently picked up a barely running project. It has been moderately molested by a previous owner.
The #1 carb was popping badly, so I did a valve adjustment and ripped the carbs apart, to verify proper order.
Got it bad together after multiple small issues, vacuum leaks, etc.
Still runs poorly. Revs go from idle to 4-5000 rpms.
The plugs were turning grey/white when I had them out, indicating lean operating conditions.
I am scratching my head and hoping someone has scene this before.
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post #2 of 6 (permalink) Old 07-19-2019, 12:21 PM
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When you say revs go from 0-4000-5000, are you talking about the idle? If so, there is a vacuum leak probably at the intake boots.
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post #3 of 6 (permalink) Old 07-19-2019, 01:59 PM Thread Starter
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I tried to post a video but no dice.
I spent the morning going through the position of the butterflies and cable tension.
I know the boots are good.
I did find and fix a few vacuum leaks.
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post #4 of 6 (permalink) Old 07-20-2019, 08:40 AM
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After verifying the valve lash and adjusting, did you clean the carbs thoroughly? If they were neglected by PO you may need to clean them a couple of times or have them ultrasonically cleaned to get all the crud out of the internal passages. Pay particular attention to the pilot jets.
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post #5 of 6 (permalink) Old 07-26-2019, 06:31 AM Thread Starter
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I adjusted the valves and cleaned the carbs. I was told there may have been some engine mods but have no way to confirm.
It almost ran ok for a bit till it got hot. Then it would barely run and sounds like it was only firing on a couple cylinders.
I am going to check the ignition electrics next.
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post #6 of 6 (permalink) Old 07-26-2019, 09:40 AM
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Carbs fluctuating at idle?

1st question, have you changed anything ,on the bike after the cleaning and valve adjustment, specifically the air box ,pods ,stacks ,or you left the mods,the way the bike entered your hands, as posted earlier ,a deep internal cleaning wouldn't hurt ,sometimes an unstable idle is a sign of your carbs not being balanced, I would bench sync them,first , make sure all butterflys are equally spaced, using a tee pin, or equivalent,then put them on a vacuum synchronizer and balance them out from the -air -fuel screws , are your float settings correct?,there is a tool on the market called COLORTUNE, it will fine tune each cylinder to each carb by color, there is a video online showing what it does,last time I checked it was about 80.00$,very accurate according to some people, you fine tune the cylinder by adjusting the air -fuel, to the color at the top of the color tune plug it will turn dark purple ,which would be the color of the spark when adjustment is spot on. hope this helps--FranksWorkshop
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