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Discussion Starter · #1 ·
I've been running 2 washers on my needles for about 15 months, and today I decided to try 3 washers per needle. Initial impressions is that the power delivery is slightly more smooth, but at the same time, the RPM needle is also slightly slower coming back when I rev the engine. Is this normal? Has anyone else tried 3 washers?
 

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for carb tuning, the main thing is to get the main jet the proper size so that at WOT 100%fuel is the right amount.....from there you can adjust the needle to get the right richness.....ie, if the main jet is too rich(as they are out of the box) and raising the needle richens the system, then all that does is smooth out the power by killing power production with too much fuel.

So, trying to get the most out of your bike all starts with the main jet and then tune down the fuel circuits from there, finishing at the pilot screws.

Stock bike, I generically go down to the 135 mains, shim the needles and go a good 2-2.5 turns out on the screws.

On my tuned motor i was down to a 128 main and zx7R needles....ripped straight to redline :D
 

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Discussion Starter · #4 ·
I ordered a set of carbs cheap to experiment more, but honestly, I came close to buying Ivan's and dynojets many times but the cost, coupled by the fact that not everyone got results, kept me from buying. Where do you get your jets and how much?
 

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If you are running the stock needles, even shimmed to .040" or .060" you are still going to need main jets in the 147.5-152.5 range.

There is no way you could run 130 something mains with oe needles, and jetting is alot more than get your main jet correct and the rest will follow.
Every part of the carburetion affects the other parts, and WOT does not equate to being on the main jet. ( I have no idea the root diameter or taper of a zx7 needle compared to an oe needle, but the needles that come with a dyno jet kit etc do ask for a 132 main jet --or something like that--so certainly a skinny enough and fast enough tapering needle could require the tiny main fuel jet)

badassjake's advice is just enough to get you in trouble, not enough to fix it. What he runs or says he runs has no bearing what so ever on what your bike needs!!

-idle mixture screw--most affective at idle, barely affective at 4000 rpm (crank these out to about 2.5-3 turns out and idle will be pig rich and the 4000 rpms stuff will still be way too lean....1 1.5 turns out is all you need on these, they are only there for adjusting the idle fuel mixture, not for fixing off idle lean conditions-for that go to your pilot air jet or your needle position or both)
-pilot fuel jet--most affective at idle, barely affective at 4000 rpm (ie...go up one jet size on this and idle will be pig rich while the 4000 rpm stuff will barely change)
-pilot air jet--most noticeable changes 3000-5000 rpms, barely noticed at idle ( ie...go down 1 size on this and idle mixture will barely change, but the 4000 rpm stuff will go about 1% richer)
-needle jet--starts all the way down at about 2500 rpms-and works with the needle root diameter and taper all the way to true main jet, 14,000 rpm +
-needle--just like the needle jet, kicks in just off idle and works to the main jet, but the most significant areas of change and regulation are the cruising rpms, in the true midrange
-emulsion tube--this is affected greatly by fuel level, as more air bleed holes open up the lower the fuel level, and the fuel level in the bowl does drop the longer your ride it WOT
-float hieght--here you go, fueel level, affects the entire rpm range, but does little at idle, unless it is really low or really high
-main fuel jet--most affective those last couple thousand rpms on a very long WOT pull, but it affects all the way down to idle in a decreasing manner
-main air jet--this is most affective in the just before true "main fuel jet" affectiveness, say the 8000-12,500 range ( make this smaller and the true main fuel WOT reading will barely change, but the numbers coming off a corner at say 10,000 rpms will go up noticeably)
-throttle slide cutaway--well this works uniformly from say partial throttle (3000 rpms) all the way to the slide being completely open

So every system has some affect on the rest, and as such you will need to make adjustments to other areas when you change something (ie...shim your stock needles .040", you should change your main fuel jets about 3 or 4 sizes smaller, unfortunately the taper on OE needles is generally too slow so that the hard acceleration off the corner suffers (lean), but your "true" main jet a/f would be correct)

(ie...#2--you change you pilot air jet, from a 125 to a 122.5, you can turn your idle mixture screw into about 7/8 turn out for proper a/f at idle-you also won't need to shim the needle so much if you are trying to "fix" a lackluster performance area in that 4-6000 rpm range)
 

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Discussion Starter · #10 ·
^ It will take 2 days to absorb all that info. The point being, my 3 shims, or even 2 shims is enough to smooth out low-mid range and bring the bike on the rich side. I think what badassjake is suggesting is that the bike will be rich after 10K+ (stock). If I understand his reasoning, he wants to lean out the top end to harvest more power, whereas the shims take care of the lean condition on the lower power band. I was told to go 135 mains, however.
 

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after 3 years of dyno tuning 100+ carbed bikes, they all fell into the same deal of going smaller main jets and tuning from there.

From my experiences, only when working with Harley/Vtwins, did major modifications to the needle be necessary when trying to fuel 2 massive cylinders from 1 carb.

Inline 4's with extensive engine mods creating stronger intake draws will too need smaller main jets, as now the vacuum it's pulling sucks more fuel through the jet.

It's all relative and absolutely nothing is given as law, and works every time for everyone....humidity, alt. ,air temp play huge factors.

So unless you get an A/F meter kit(250.00) and tune to what you want, or make a trip to a quality dyno with and eddycurrent system, then it's all experimenting.
 

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If we are going to see has can swing their dick more, I have 28+ years of dyno experience and tens of thousands of bikes run on it.

I do agree with you on nearly every stock jetted bike made that I have ever run is too rich on the main jet and generally too lean in the middle- but you can't just go smaller on the main jet to fix this. Your way top end of midrange will be so lean you will actually loose performance, just get a bigger hit making you think you gained something when you ride it, but lap times and pulling off corners will actually be slower.

Stock needles hardly ever work, if you really want to be in the top 5-10% of the performance available to you- shimmed or otherwise, for a street guy they can be shimmed and made better-but typically all this does is make them too rich down low and still too lean just before main jet. Just not quite as bad
 

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no dick swinging, just relaying that i have experience and am not an internet know it all.

For our area, Atlantic coast this is what works best for street riding, giving performance and mileage.

Now put your cock away, you're scaring the noobs....LOL
 

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Discussion Starter · #14 ·
May be I should go half way and buy a set of 142 mains. This way I get the egos of both the cocks and cock swingers :). But seriously, I'm utterly confused between the two of you. I'm going to order a set of mains tonight and it will need some convincing before I go for one over the other.
 

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FWIW with my Dynojet needles i dropped down to dynojet 118 mains in the outer cylinders and 120 mains in the inner. Though you can't compare sized directly due to specific flow rates among the different manufacturers, the orfice size on my jets would work out to about 110-113 Mikuni mains.

This would lead me to believe that the stock needles are alot of the problem.
 

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Discussion Starter · #16 ·
FWIW with my Dynojet needles i dropped down to dynojet 118 mains in the outer cylinders and 120 mains in the inner. Though you can't compare sized directly due to specific flow rates among the different manufacturers, the orfice size on my jets would work out to about 110-113 Mikuni mains.

This would lead me to believe that the stock needles are alot of the problem.
That's way too low. DJ and Ivan's use confusing numbers to discourage your noob-DIYers like myself from getting the jets done cheap. Even if your numbers are correct about Mikuni, our bikes will lean the way out.
 

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Read my previous post !

"If you are running the stock needles, even shimmed to .040" or .060" you are still going to need main jets in the 147.5-152.5 range."

I run 150's and my jetting is 3.2% on the true main jet ! and makes just over 108 hp, most modern day 600's I run on this same dyno are between 98 and 110hp, so this is a very stout 600 ! The midrange numbers on my zzr are upwards of 8 hp better than any other "modern" 600 I have ran-so I can easily walk on just about any 600 out their from a midrange type run...I have 16/41 gearing ( +1/+1), alot of the guys I "walk" from, are running -1 or +2 or even -1/+2 in some cases

^ yes all the "aftermarket" jet kits use numbers and even flow rates different from mikuni and kiehin so their jet numbers aren't easily translated to and actual mikuni or Kiehin jet--the only part of those kits you "need" is the needles !
 

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That's way too low. DJ and Ivan's use confusing numbers to discourage your noob-DIYers like myself from getting the jets done cheap. Even if your numbers are correct about Mikuni, our bikes will lean the way out.

Like i said, you can't compare flow rate/diameter directly among brands. All i know is that my mains are ALOT smaller than stock (visually) and the bike runs better throughout the revs than it ever did.

Dynojet also uses restrictors on the main jet air passage to increase pressure on the fuel side of the carb which may result in conditions that allow to run a smaller main jet size.

My .02 is to pony up the hundred bucks and get a jet kit for your bike instead of fucking around with the shitty stock needles and chasing main jet sizes without any proper equipment to monitor/log A/F ratios.

I had shimmed my stock needles with 2 washers like many on here have done and still felt like there was room for improvement. After installing my DJ kit, i wonder why i ever wasted my time with the stock needles and jets.

Truthfully, my DJ kit was the best money i have spent on my zx6r.

But hey, if you want to go your own route than more power to you, but please post your results so that other may go the same route if they so choose.
 

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Just ordered a set of 142s... bang in the middle of what badassjake and 07zzr suggested. $20 shipped.
based on your pm and what you are "trying" to accomplish-you just wasted $20.00

There is no way with stock needles you could possibly run smaller than 147.5's and still be in the productive power range, You (according your your PM) need to work on the off idle circuit (pilot air jet) and the early stages of the needle (root diameter and when the intial taper begins)
 
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