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Discussion Starter · #1 ·
If anyone out here knows.... The last three bikes I've owned (900 Ninja, ZX11, ZX12), I have removed the carbs (throttle body), unplugged the air screws and checked their settings. I have yet to find any 2 cyl. set alike, and the bikes have always responded very well to having the settings equalized.
Why isn't this done at the factory? What's the point of plugging them when they are incorrectly set?

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I beleive that on an inline 4 , the 2 outside cyls have bigger jets than the 2 inside cyls. I think the reason is to keep the 2 inside cyls cooler ??

I could be way off here man soooo(I probably am, I've been drinking again!)...
I remember ripping the carbs of my old CB750 (air cooled) and the two inside jets were smaller?? actually I'm thinking I was drinking quite heavily that day also ?

Oh wait are we talking about the Main jets ?? NOO!!! Oh...ummmmm...maybe I'll just go now .


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<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Squidwannabe:
I beleive that on an inline 4 , the 2 outside cyls have bigger jets than the 2 inside cyls. I think the reason is to keep the 2 inside cyls cooler ??

I could be way off here man soooo(I probably am, I've been drinking again!)...
I remember ripping the carbs of my old CB750 (air cooled) and the two inside jets were smaller?? actually I'm thinking I was drinking quite heavily that day also ?

Oh wait are we talking about the Main jets ?? NOO!!! Oh...ummmmm...maybe I'll just go now .


<HR></BLOCKQUOTE>

Nice one squid, actually, with what little I know about the subject(very little), I'd say you are on the right track. But, what the hell do I know :D


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Squid' is right on the mark. The inner two should be the same and the outer two should be the same. It is because the outer two cylinders run cooler.



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John

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I thought that just applied to the main jets and not the mixture screws, but it's logical that both would be that way. Leon did say he found "no 2 the same" however. Since I doubt the factories flow test each carb and set them accordingly, I'd guess the differences are due to sloppy tolerances or vibration moving them a bit over time.

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I was talking main jets on inline 4 cylinder Kawis with racing carbs set-ups. :confused:

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John

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Discussion Starter · #7 ·
When I said I found no 2 the same , that's just what I meant. Example - Cyl1 = 1/2 turn, cyl2 = 0 turns, cyl3 = 2 turns, cyl4 = 1.5 turns. These are obviously arbitrary settings. Let me flip it around - has anyone ever checked their idle mix settings and found them to all be the same? Or any two cylinders the same?

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<BLOCKQUOTE><font size="1" face="Aril, Helvetica, sans-serif">quote:</font><HR>Originally posted by Tristan:
I'd guess the differences are due to sloppy tolerances or vibration moving them a bit over time.
<HR></BLOCKQUOTE>

I heard from a couple of different mechanics that no 2 cylinders are the same... the volumn of one cylinder might be RELLY close but they're not the same. I also heard that some cylinders vary alot... thus causing different mixture screw settings.
I also heard that if you take 2 identical bikes, pull the head and do the clearance test with clay, that one might have 0.027" clearance and the other bike might have 0.041" clearance. (from an actual test between 2 R1's)
- Jeff -


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I believe that 'how' the arrive at the
settings is a compromise between best performance
and meeting emitions requirements. That's
why they are capped so you can change the
settings.

Food for thought. :)

Chris

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Discussion Starter · #10 ·
Ithought about that, Chris. They must take the settings from 1 particular engine and apply them to all the engines in that series. If so, then you know that the settings the bike comes with are probably in error. I've got some parts ordered, and when they get here, I'm going to equalize and resynch my motor. I'll let you know what difference it makes.

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<BLOCKQUOTE><font size="1" face="Aril, Helvetica, sans-serif">quote:</font><HR>Originally posted by Leon90zx11:
Ithought about that, Chris. They must take the settings from 1 particular engine and apply them to all the engines in that series. If so, then you know that the settings the bike comes with are probably in error. I've got some parts ordered, and when they get here, I'm going to equalize and resynch my motor. I'll let you know what difference it makes.

<HR></BLOCKQUOTE>

This sounds pretty logical to me. ;) Good luck with the tuning. :)



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John

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That's right on the money. When I resynced
the carbs on the R1 I needed to drill out
the caps over the idle mixture screws and
reset them b/c I was getting some nasty
backfiring when I shut the throttle off hard
in the high revs. IE after dropping the
front wheel and needing hard breaking or
down gearing hard into a corner.

Chris


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Yes Leon there was, now I don't have them
perfect but it doesn't backfire nearly as bad
as it used to. With the caps drilled
out I can adjust them on the fly which I will
do when my lazy ass is ready. :D

Chris

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