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As you guessed, the off idle hesitation. I don't know much about bikes, but would it be possible to install a wide-band o2 sensor to see exactly what's going on? I'm trying the 2 1/2 turns thing right now so we'll see how that goes. I'm just afraid of fixing one thing and causing too rich/lean a mixture elsewhere.
I start a separate thread here:
http://www.riderforums.com/showthread.php?p=565477
If you have an idea of wide-band O2 sensor ...
 

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You need to know where your pain is! For example: If the pain is off-idle hesitation, then changing the main jet will not help.

I have actually marked my throttle grip with 0, 1/4, 1/2, 3/4, and full indicators with tape. This will help you zero in and know what needs to be changed. You can see on the charts, there is some overlap.

Most off idle hessatition is caused by the pilot jet and/or idle mixture pilot screw.

Good luck,
 

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Been reading this thread and actually wanted to start a new thread to not hijack this one but it seems that i can only reply to, but not make new threads so my question goes here.

Will the Ivan jet kit only help out with hesitation or will it also increase HP ?

Wanted to bump my HP a bit from the stock 74 and wanted to know if a jet kit would be the way to go ?

My motorcycle is a 2001 Zr7 F1

Hmadsen
 

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:welcome: from Scotland!

Nothing is going to give you a massive power hike, but there are useful gains to be had from the following modifications:
1-Aftermarket exhaust can,
2-K&N (or similar) air filter
3-Jet Kit
4-Ignition advancer

Most of the gains are in the low to mid rev range rather than in 'maximum' power, but they are accessible and useable power.

Beyond these simple (and reversible) mods, you're looking at things like big-bore piston kits, turbo-charger, nitrous etc which tend to be less than cost effective (i.e. sell up and buy a 'Busa)

Graeme
 

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I purchased a Factory Pro jet kit, and after playing with the different settings and sized finally found a good one. When I went with the recommended setting from calling Factory Pro, and using their tuning sheet, I saw very little gains. Mainly seen in less lean surging, with more of a smooth ride, but extra gas shot out the tail pipe and I got 36-42mpg, which is down from 55.

So I played around with it, and found that the FP pilot jets and needles (on clip 2 of 5), combined with stock jets and mixture screws 2.5 turns out seemed to be the best. No lean surging, no real increase in power except slightly in midrange, and 47-50mpg.

Im happy :D
 

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Thanks for the answers.

Where to buy the jetkit and ignition advancer cheapest ?

Also i have read that taking the EGR valve off should give a little better running properties ?

Hmadsen
 

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This is the original equipment of the German carburetor.
The inner needles are shorter than the outer.
Your list is wrong.
The inner cylinder has to be cooled better than the outside, so there are the shorter needles inserted.




This is Excllent Info!
Thanks for posting the measurements for the Ivan's needles.

One thing though, I think you have the labeling of the inner(#2 & #3) and outer (#1 & #4) needles swapped.
The outer needles should be the shorter N6NC and the inner needles should be the longer N4MD.

Other than that, your diameter and taper measurements looks essentially the same as mine...well at least as close as a Chinese digital micrometer can measure them.

Steve
 

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Discussion Starter #68 (Edited)



This is the original equipment of the German carburetor.
The inner needles are shorter than the outer.
Your list is wrong.
The inner cylinder has to be cooled better than the outside, so there are the shorter needles inserted.
Hello Tommi,

Welcome to the forum. :)

I agree with your table, it matches the US service manual.
- the N6NC needles are used in the outside carburetors #1 and #4.
- the N4MD needles are used in the inner carburetors #2 and #3.
This was what I was pointing out to graeme.medley.

But, if you measure the two needles you will find that the N4MD used in the inner carburetors are about 2mm longer than the N6NC.
This seems backwards because the inner cylinders should be run a little richer to cool them better.
I believe the mixture is richened up on the inner cylinders by the use of emulsion tubes with 18 holes compare to 14 holes for the outside cylinders.

I know other guys have mentioned this fact before on the forum.
A quick search found this:
http://www.riderforums.com/showpost.php?p=86067&postcount=7
 

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Oh ****. I just checked. The long needles are actually inside (Carbs 2 3).
Sorry for the **** that I wrote.



Hello Tommi,

Welcome to the forum. :)

I agree with your table, it matches the US service manual.
- the N6NC needles are used in the outside carburetors #1 and #4.
- the N4MD needles are used in the inner carburetors #2 and #3.
This was what I was pointing out graeme.medley.

But, if you measure the two needles you will find that the N4MD used in the inner carburetors are about 2mm longer than the N6NC.
This seems backwards because the inner cylinders should be run a little richer to cool them better.
I believe the mixture is richened up on the inner cylinders by the use of emulsion tubes with 18 holes compare to 14 holes for the outside cylinders.

I know other guys have mentioned this fact before on the forum.
A quick search found this:
http://www.riderforums.com/showpost.php?p=86067&postcount=7
 

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Hi Bolserst, I've just read right through this post and am intrigued by your results. I have just fittted a Dynojet Stage 1 kit to an otherwise stock bike and have found as per this post the kit does not resolve the 1500 to 300 flat spot. I of course have the stock needles removed from the bike , can you confirm are all 4 needles identical. thanks
 

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Hi Bolserst, Ive just purchased on ebay a Dynojet stage1 kit for my ZR7 and had it shipped over to me here in New Zealand. Very dissappointed with the results, the motor is definitely more free in the higher rev range but no improvement at all to the dreaded off idle flat spot. Interestingly Dynojet supply a range of jets and recomend an #098 jet if running standard filter and exhaust (which I am). Luckily they provide in the kit #100 #102 #104 #106 jets.( So Ive earmarked the #102s) to use in conjunction with the needle modification.
Ive read over this thread a number of times and learned a lot from your explanations and am really keen to try it.
Just got to buy myself a cheap micrometer and a drill press.
Will come back with feedback once I have organised the tools. Thanks.
 

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Discussion Starter #73
Hi Bolserst, Ive just purchased on ebay a Dynojet stage1 kit for my ZR7 and had it shipped over to me here in New Zealand. Very dissappointed with the results, the motor is definitely more free in the higher rev range but no improvement at all to the dreaded off idle flat spot. Interestingly Dynojet supply a range of jets and recomend an #098 jet if running standard filter and exhaust (which I am). Luckily they provide in the kit #100 #102 #104 #106 jets.( So Ive earmarked the #102s) to use in conjunction with the needle modification.
Ive read over this thread a number of times and learned a lot from your explanations and am really keen to try it.
Just got to buy myself a cheap micrometer and a drill press.
Will come back with feedback once I have organised the tools. Thanks.
Hello D Wright,

I believe the DJ kit comes with weaker CV springs to install above the diaphragm. You didn't specifically mention installing them. If you didn't, perhaps this is part of the reason you still have some hesitation with the DJ kit.
In any case, if you plan to sand down your stock needles, you should use the stock CV springs to get the correct diaphragm stiffness.

A couple things I hadn't mentioned previously:
1) Before sanding down your needles, you might practice on a cheap aluminum rod from a hobby store. This will help you get the feel for how much pressure to apply and the proper technique to get uniform diameter over the length of the needles.
2) When sanding be advised that since the needles are anodized, the outer layer of aluminum will be harder and sands down more slowly. I've helped a few local riders sand down their needles and have noticed that the hardness of the thin anodized layer seems to vary from needle to needle. Once you get thru the thin anodized layer the sanding goes MUCH quicker. I could feel the sandpaper biting in more to the metal once I sanded down past the anodizing. Just go slowly and measure often. Even if you accidentally remove 1.5mil or 2.0 mil it will be fine, but you need to make all the needles match. This will reduce mpg slightly, but should still be above 45mpg.

Good luck! and let us know how it goes.
 

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Hi Bolsesrt, thanks for the reply. You are correct the DJ kit does come with new springs. In the DJ instructions it said quote' For racing or hard street riding install the Dynojet (DSP031) springs in place of the stock springs for better response' . From this explanation as I'm more of a shall we say 'sedate' rider I opted not to use them. From your comments it sounds like it could be worth swopping them over prior to progressing with the mod to the standard needles, and of course I can achieve that with the carbs in place. Interestingly all the DJ supplied needles were identical contrary to the stock ones.
 

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Hi again , fitted the DJ springs , certainly an improvement but still feel the flat spot is still there although significantly better. Will definitely do your needle mod / fit the #102 jets /revert to the stock springs. pretty comfortable with the procedure , thanks again for the further detail. Will update when I've done it.
 

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Hi Steve, I've now fitted the #102 jets returned to the standard CV springs, done the needle mod ,and set air screws to 2 turns. The results are as you described DRAMATIC. I accelerated up hill at about 30 mph from 2,000 RPM and the motor felt fine.
All hesitation off idle is gone, I overshot on the sanding taking off about .04mm (my micrometer is metric) I calculate that to be about 1.5 thou of an inch. My standard needles started out at 2.45 mm now down to 2.41mm as measured by my chinese micrometer. Thanks for taking the time putting all this info on the web, wish I'd read it before I purchased the jet kit , I suppose at least I got the value of the #102 jets.
 

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Discussion Starter #77
I've now fitted the #102 jets returned to the standard CV springs, done the needle mod ,and set air screws to 2 turns. The results are as you described DRAMATIC. I accelerated up hill at about 30 mph from 2,000 RPM and the motor felt fine.
All hesitation off idle is gone, I overshot on the sanding taking off about .04mm (my micrometer is metric) I calculate that to be about 1.5 thou of an inch. My standard needles started out at 2.45 mm now down to 2.41mm as measured by my chinese micrometer. Thanks for taking the time putting all this info on the web, wish I'd read it before I purchased the jet kit , I suppose at least I got the value of the #102 jets.
Congrats! Sounds like you did good.
Still amazes me how little metal you have to remove from the needles.

I would be interested to hear what sort of average gas mileage you are getting once you run a few tanks through it.
Also, how does the top end roll on power with the #102 main jet and stock needles compare to when you had the DJ needle setup.
 

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I have just bought a 2000 model ZR7 and it is the leanest running bike I have ever seen.Hope to put some of this jetting info to good use.At least it came with an extra set of carbs,so down time will be less.
Thanks for all the info.


Tom
 

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I've read the whole thread, and find it very interesting stuff! At this point my ZR is not very economical with the fuel (I get about 200 miles out of a full tank, not sure what that does in MPG, but it mean I need 1 litre to go about 17 km (just over 10 mile per 1 litre).
and i hear and read stories about the super fuel efficient ZR7.. doing up to 23 km per 1 litre) i do know my bike runs rich, but not overly so.

one of the things i do no like is working on a product that has already been over used. In this case the carbs, they have been on this bike for 40.000 miles and i suspect the main needles, tubes that house them and some other parts to be fairly used up (worn). and there for hard to tune correctly. This made me want to go out there and buy a overhaul kit for the carb (needles, tubes, gasket, springs.. the whole nine yards).

BUT... so far no luck. all i could find was a pilotscrew kit with a float-bowl-gasket and float-valve. no needles, no tubes and so on.

is there someone here that has done this before and has like "the complete list" of part numbers or a address where one could obtain these parts?
 

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ive NEVER seen a carb that has "worn" those parts out....pilot screws get worn on the threads and the tip from being adjusted ...a needle would only wear if something was wrong..seriously wrong(read bent or out of alignment)...same goes for the tubes...the only other way to wear any of this stuff is if you left some bad gas in them for 5+ years and it corroded them enuf to cause wear when you cleaned them..thing is even so id be willing to bet aside from the tubes that they would all still be in spec...in all the years of working on engines of all types ive never seen that kind of stuff wear unless it was mis-adjusted by someone in such a way to cause wear...and even the ones that were beat to death by someonelses faulty work the needles were still within factory spec
 
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