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Discussion Starter · #1 ·
Hello, just joined your forum and I am happy to be part of your group. My 94ZX11 I recently bought has a flat spot at low RPM . I thought it needed a tune up or carbs cleaned , flat spot still there , some pals say they don't notice it but after surfing the net , found alot of talk about this with other ZX11 owners. A CARB MOD shim needle valves .025" (small washers) and adjust idle mix screws 4 turns outto richen mixture , solves problem . can anyone tell me if they have done this and is it really that simple? THANKS
 

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4 turns are too much. Shim your needles between 0.020" and 0.040" and adjust your air screws between 2½ and 3 turns. There are no precise numbers as all bikes do not respond the same.
Most shims (washers) you will find are ~0.020" thick so it is a matter of using one or two.
Personnally, I would begin with 0.020" and 2½ turns but you could need a bit more; only trial will let you know.
 

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4 turns are too much. Shim your needles between 0.020" and 0.040" and adjust your air screws between 2½ and 3 turns. There are no precise numbers as all bikes do not respond the same.
Most shims (washers) you will find are ~0.020" thick so it is a matter of using one or two.
Personnally, I would begin with 0.020" and 2½ turns but you could need a bit more; only trial will let you know.

:thumbup :thumbup

same advice I gave on another thread about this same topic.
 

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Discussion Starter · #4 ·
Hi Claude, Thanks for the info , have you seen or done this ?, will it help with the dead spot at low RPM or open the door to more mods ? Also the shims, should they be brass like the needle or is steel ok ? I don't think it could rust up in the carb if I was to use steel . THANKS
 

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Ricci, I've done this long ago on my ZX-11 as well as many other members from our ZX-11 dedicated forum. The washers could be steel but personally, I would, at least, use plated ones. For me, the best option are nylon or stainless washers. Aluminium could be nice too but they are usually quite thicker. If you can't find any, I could mail you some of them in stainless.
 

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Oh and this "modification" is working pretty well by itself. It simply richens up the mixture a bit where it's a bit lean, usually between 3500~5000 RPM.
 

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Discussion Starter · #7 ·
Thank you Claude, I didn't even think of nylon washers ,that would be the best way to go. I will let you know how it turns out .
 

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I know this is a fairly old post, but I am new to the forum and just read it. Does anyone have any pictures of this procedure and a source for the washers?

Any help would be greatly appreciated.
 

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The washers I'm using are just regular M3 washers. Their dimensions are ID : 3.25 mm, OD : 6.65 mm and thickness : 0.60 mm (~0.024").

Diameter of needles is 2.92 mm so ID need to be around 3.0 mm or more. Best thickness to use is about 0.020" as you can use two to reach total shimming of 0.040".

Bring your vernier to your local hardware store and measure regular 1/8" washers (1/8" = 3.175 mm). They should be pretty close to the M3 units I'm using...
 

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Thank you Claude. One last question: is it 2 1/2 to 3 turns from their current position or from seated for the air screws?

Thanks again,

Eric
 

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Eric, to adjust air screws, you need to screw them in completely (not tightly though; just until they slightly seats) and from there, you count the number of turns you take them out. If you care a bit about fuel mileage, begin with 2½ turns. It could work OK and not decrease mileage.

OEM carbs are sealed (little aluminium plug over the screws). You need to take those plugs out first. Read about this on Dynajet instruction sheet here: http://www.dynojet.com/pdf/2151.pdf

Have you found shimming washers? If yes, what are they? 1/8"?
If not, PM me.
 
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