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Discussion Starter #1
Hello me again with 87 ZX1000a2. I was riding my bike when suddenly the my bike starter performing very poorly. Flat spots in the rev range everywhere. I go about a mile or two, come up to a stop sign, make a left and it felt like my 100hp dropped to about 20hp. it accelerate ok in first gear, but if i get on the throttle it would actually slow down. I rode the bike to my friends house...

We took the carbs off, totally cleaned them out. Inspected them, didnt see any problems with the floats-- the bowls were dirty but we could see nothing wrong. The fuel tank seems fine, gas comes out of pretty quick. Fuel filter is fine. I dont know if i should try to find a junkyard with used parts cheap*, carb rebuild kit, or MIKUNI FLATSLIDE SMOOTHBORES carbs 36mm/38mm/40mm

To be honest I dont know the first thing about carb performance engines. But i was thinking wiseco 11:1 pistons these Mikuni carbs (I dont know what size) Vance hines exhaust and just enjoy that. I doubt the carbs will do much for performance but i was thinking it would be good preventive maintence. I didnt plan on buying them this early either, i was going to save up over the course of the winter. $599 Ouch. what do you guys think??

Im going to check the compression too, but i dont think thats the problem. What kind of numbers should i see across the 4 cylinders like 170psi?
 

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Discussion Starter #2
Mikuni 34mm flat slide smooth bore

I found carbs on e-bay that were taken off a kawasaki. Currently bidding is $100 with no bidders and not a ton of time left. Do you think these are worth a try?
 

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I think your problem is likely far less complicated than you do. Don't buy new carbs. They don't suddenly wear out. You more than likely have a fuel delivery or ignition issue, not carbs. Those bikes have pulser coils that are notorious for failing. They'll kill two cylinders when they go. Check them with an ohm meter.

No idea what the compression should be. 170 would be fine though.

You really ought to buy a service manual if you have not already done so.
 

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Discussion Starter #4
Thanks for the input, but the bike doesnt seem to have a miss. Just when you open the throttle the power drops. Its like it gets enough fuel up to about 10% throttle, then its starved.
 

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Could be carbs... Sounds like it's "flooding" out... how do the plugs look???
 

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Discussion Starter #6
I wish i knew how the carbs looked, but i dont have a 16mm deep well socket to take them out yet. im THAT broke at the moment. with my next check ill take a look at them do a compression test.

To watch/smell the exhaust it doesnt look rich.. but I don't know...
 

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Discussion Starter #7
I found a crack in one of the diaphrams, and the others are showing signs of aging as well. To bad it costs $130 for EACH diaphram. I bought new (used) carbs from a salvage yard hoping they work out. $175.

One of the sparkplugs was all fouled out, the other three looked fine.
 

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One thing I could suggest in the future is that when a bike runs but runs really weak is that usually you are running on less that all cyllinders. The best thing to do to help trouble shoot it is to CAREFULLY check the temps on all the header pipes. Which ever has the problem will almost always be much cooler. Also, if it's an ignition problem on older bikes like yours they frequently take out 2 cylinders at a time because you have 2 pairs of cylinders running on one coil/system each. If you lose a pair that run on the same coil it points you in the right direction. If you lose one you can look at the plug or carb on that cylinder specifically as it's 99% one or the other.


:2cents: that's helped me before.
 

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Discussion Starter #9
A new update. i pulled the plugs out, all four are fouled really bad, but one is totally covered in soot. With the wires plugged in, all four plugs are still sparking. While I think two of the plugs are sparking weaker then the other two, could this be a cause? I am going to get new plugs, wires.. see what happens if that dont work im taking it somewhere.
 

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Run fresh plugs for about 500 miles then pull them again and get a good reading. I'm guessing your bike is going to foul up again but it's worth giving it a chance that you won't have to jet and clean the carbs.

Also, change your air cleaner, if it's clogged up that could cause a rich condition too. It's odd for all the cylinders to run rich unless there's a bad air cleaner or some numbnut put in waaaaay to big of jets, or ran it with the choke on all the time.

I wouldn't put too much worry into the slightly weak(er) spark you saw as all that build up could cause a weak spark. Check again in 500 like I said.

Also make sure you have the right heat range plugs installed, too cold a plug can lead to build up I believe I have heard???

Write back to let us know how it's going.
 

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Discussion Starter #11
Helpful as always apexi..

The bike had no air filter when i bought it. I put the new carbs on and rode it to a shop to have it fixed. I will admit the new carbs make it run ALOT better. before it felt like it would have to fight to hit 70mph. That day i was able to reach like 115 before i backed it off. It would still want to die if i went from like 1/4 throttle to full quickly. rpms would drop . but if i gradually opened it responded much better then before.

I almost think if i had an air filter and my factory air box on it would of ran decent. right now its getting new plugs, new rear tire, new rear brakes, new pads up front. and once a new air filter stock air box is --if it still doesnt run right they have my permission to tune and sync the carbs.
 
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