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thanks for the info. I sent him a pm and we'll see what he has to say. meanwhile ill have fun tinkering. I also got some #38 pilot jets to try out.
 

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Good signs for the future

So i installed the new needles this morning fully expecting the bike to not even start up because their profile is so different. But i get them in without taking the carbs off and figure ill at least start it up and see because the weather is so crappy here that i didnt really want to go out for a proper test ride. I start it up at about 1/2 choke and within about 90 sec I had it off the choke and purring fine (normally i have to run it on 3/4 choke for like 5 min). Anyway, i give it a few revs and quickly realise that it has no more hesitation off closed throttle and it doesnt stumble anywhere allong the power band (of course that is under no load) but initial results seem promising so ill have to let you know how it is after I can get in a proper test ride. Just the difference in the sound of it revving makes me all tingly and excited though :D it sounds like a freakin superbike now! no more pause when you crank the throttle. yay!!!!!!
 

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Well.... something is definitly not quite right...... Im not really sure what it is but having to push my bike nearly a mile to get it home tells me that something is up. It may just take some tweaking but im not quite sure where to start. Maybe the mixture. It seems like it does ok (maybe a bit rich) untill it warms up and then it just died. my battery was low too that might have had something to do with not being able to restart it but I tried every once in a while on the long "walk of shame" home. On the plus side there were no shortage of people stopping to offer me assistance (maybe theres hope for the world yet :))

Any suggestions would help me. I may just have to go back to the stock needles and go to #38 jets. Thanks for the help.
 

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Discussion Starter #44
... It seems like it does ok (maybe a bit rich) untill it warms up and then it just died.
Mixture does richen up as the engine warms up, so that makes sense.
A coupla questions...

1) Did it die at idle? or when you were twisting in more throttle.
1a)If at idle, was it after idling for a while? or after a bit of wide open throttle and then returning to idle.

If it died at idle due to too rich a mixture, you might check what you had your pilot screws set at. With thinner(richer) needle, you won't need as many turns out on the pilot screws to get a rich enough idle mixture. You might try the factory recommend 1 1/4 turns, if you aren't there already.

You might try the "blip" test to get an idea on your idle mixture
http://www.riderforums.com/showpost.php?p=476963&postcount=4

2) Before the engine was completely warmed up, did it accelerate well? or kinda feel like it was bogging down as you got past 1/2 throttle twist.

If bogging down at higher throttle settings, this is most likely from the quick taper on the needles. You might be able to offset this with smaller main jets.

3) Do you still have OEM air-filter and exhaust? or aftermarket.


Steve
 

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Setup: no airbox mods. Freshly cleaned K&N. Two bros racing exaust. Stock jets as far as I know.

1) Not sure really. I had just gunned it for about a block, then slowed down to take a corner and when I was accelerating out of the corner it started to sound like it was missing real bad (like running on 2 cylinders almost) and no throttle response. I held in the clutch and coasted for a bit trying to rev it with no response and then it died. I coasted into a parking lot and waited for a bit then tried to start it. It tried and fired once then wouldnt. I figured it was flooded so i let it sit for a few min and tried again.... nothing. So i started pushing because I wasnt going to leave it there. I tried to start it every time I took a break from pushing it the mile or so home but no luck.

I should re-set my mixture screws I guess :corner . they are at 2 turns.....

2)Yes it did feel a little boggy at 1/2 throttle. Felt good from closed to 1/2, and then after it got past the bog it felt fine and pulled like mad.

Any recomendation on the size of main jets?

Also is this worth persuing or should I just do stock needles and the #38 primary jets?

Thanks for the help!
 

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Discussion Starter #46
Setup: no airbox mods. Freshly cleaned K&N. Two bros racing exaust. Stock jets as far as I know.

1) Not sure really. I had just gunned it for about a block, then slowed down to take a corner and when I was accelerating out of the corner it started to sound like it was missing real bad (like running on 2 cylinders almost) and no throttle response. I held in the clutch and coasted for a bit trying to rev it with no response and then it died. I coasted into a parking lot and waited for a bit then tried to start it. It tried and fired once then wouldnt. I figured it was flooded so i let it sit for a few min and tried again.... nothing. So i started pushing because I wasnt going to leave it there. I tried to start it every time I took a break from pushing it the mile or so home but no luck.

I should re-set my mixture screws I guess :corner . they are at 2 turns.....

2)Yes it did feel a little boggy at 1/2 throttle. Felt good from closed to 1/2, and then after it got past the bog it felt fine and pulled like mad.

Any recomendation on the size of main jets?

Also is this worth persuing or should I just do stock needles and the #38 primary jets?

Thanks for the help!
From your description, flooding from overly rich mixture from the sharply tapered needles sounds likely. Either that, or you were running out of gas...is that possible?

To start a flooded bike, I have always had good luck with holding the throttle wide open and cranking for 10 seconds. If neccessary, wait a minute to avoid overheating starter, then hold throttle wide open and crank again for 10 seconds. Repeat as neccessary. As soon as engine catches and RPM needle heads for redline, release the throttle and you should be good to go.

Once you get the bike started again, you might try riding around using only less then 1/4 throttle to confirm that hesitation is gone and as long as you are staying on the straight section of the needle all is well, no dieing or idling problems.

As far as main jet size...unfortunately the only way to get an idea how this would change things is with some dyno runs at several throttle opening positions(1/4, 1/2, 3/4, full) to get some data on your air-fuel ratio at several points along the needle.

If this sounds like fun to you and have a local dyno test facility, I'd so go for it. Otherwise, I'd recommend first trying out those #38 pilot jets with the stock needles. This seems have provided a useable solution for several folks here with minor hesitation problems.
 

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Thanks! I have alot of stuff to try now. I have had pretty good luck with the same method of starting a flooded bike, the only issue was that my battery was low at the time and didnt like cranking for so long. Once I got her home and onto the charger she started right up but I didnt do any messing since I was rather tired from pushing her "curvy" frame the mile or so home:buttkick: Ill definitly turn back the mixture and see if theres any change and take it from there. As for dynos, I will have to look into it and see if there are any local.

Thanks again and ill try to keep you all updated on my progress.
 

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I was just reading through the thread again and had a major realization... I set the length of all the needles the same so the #2 & #3 cylinders have very short needles in them..... should probably fix that..... might help some things. On a different note, I turned my mixture screws back to 1 1/4 and it did seem to help.
 

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Discussion Starter #49
I was just reading through the thread again and had a major realization... I set the length of all the needles the same so the #2 & #3 cylinders have very short needles in them..... should probably fix that..... might help some things.
The straight section at the top of the needle is the same length on the OEM needles. It is only the tapered section that is longer on the needles in carbs #2 and #3. I would think all the needles should be installed with clips in the same position.

Somebody who has installed a jet kit might speak and confirm that that was the recommendation for the kits.
 

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I duno. I changed them to match the OEM length and it does seem to run smoother. I won't know untill I actually road test it later today.
I also just realized that I need to get some newer pictures up on here :)
 

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I think I may try #105 main jets and see how that does. I dont want to give up on these needles yet! By the way, I really have to thank you gents for not getting fed up with all of my posts and questions :) On that note... I was doing alot of reading and it seems that people are changing shims and position of clips on adjustable needles alot..... what would happen if i lengthened the needles more (put the clips on the top-most slot? In theory wouldnt that make the usable part of the needle more of the straight part of the shaft and a little less of the dramatic taper at the end? Or would it just mean less range of throttle/shorter power band?
 

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Discussion Starter #52
I think I may try #105 main jets and see how that does. I dont want to give up on these needles yet! By the way, I really have to thank you gents for not getting fed up with all of my posts and questions :) On that note... I was doing alot of reading and it seems that people are changing shims and position of clips on adjustable needles alot..... what would happen if i lengthened the needles more (put the clips on the top-most slot? In theory wouldnt that make the usable part of the needle more of the straight part of the shaft and a little less of the dramatic taper at the end? Or would it just mean less range of throttle/shorter power band?
Yup, you've got the right idea. Moving the clip up(which moves needle down) will have the carbs operating on the straight section of the needle longer, and at full throttle will have a leaner mixture since you won't have moved as far down the taper. One possible drawback to this idea is a flat spot in the mid-throttle range if transition to the taper is delayed too much by setting the clip too high. The carbs do need some taping of the needle with increased throttle opening to keep the mixture optimum.

It's easy to change the clip position without taking the carbs off the bike, and it sounds like your having fun experimenting and learning, so try a couple of positions further up the needle and feel out the throttle response.
 

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well I am going to order some #105 main jets, so last night i decided to pull the carbs and put in the #38 pilot jets. I did that and put the stock needles (no shims) back in just to try it out. I think I set the mixture at 1.5 turns. I just barely got it back together before i went to bed so i only started it make sure it ran. It did seem to run rich though. I guess i need to dial down the mix and maybe open up the airbox some. Just tinkering now so feel free to throw out any suggestions or experiences with this setup (i know its already been covered pretty extensively).

P.S.- does anyone have pics of the Ivan's, dynojet and moto specialties needles? I found one pic of needles and in comparison my stock needles looked nothing like the stock needles shown in the pic.......
 

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Well its still in need of some tweaking but right now I am using (#35) pilots and (#105) mains. I downsized the mains after that full throttle flooding out issue i had and im running the needles on the 3rd (center) notch with the mixture screws at 1.75 turns out. I also put about seven 3/8 holes across the top of the airbox. I still need to sync the carbs but it runs pretty well and the hesitation is much much less aparent. The acceleration is much quicker but it still seems a bit rich on the first half of the throttle. Hopefully I can balance it out well enough. I may add a few more holes in the airbox also.
 

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Without complicating things overmuch I though some of you would be interested in my findings:
I have just obtained a'spare' bank of carbs to 'play' with, and to install an Ivan's jet jit in.
As I had the carbs apart I took the opportunity to meaure them up (as best I could with a vernier caliper).
My measurements for the stock needles are very similar to Bolserst's findings, plus I have added the dimensions of the Ivans needles.


N4MD (carbs 1 + 4)

Length of parallel section: 16.33
Length of taper section : 30.16
Maximum Diameter : 2.41
Tip Diameter : 1.90


N6NC (carbs 2 + 3)

Length of parallel section: 17.47
Length of taper section : 27.45
Maximum Diameter : 2.42
Tip Diameter : 1.87


Ivans Kit (all carbs)

Length of parallel section: 14.64
Length of taper section : 27.20
Maximum Diameter : 2.38
Tip Diameter : 1.72


The Ivan's kit also uses #105 main jets as opposed to the standard #108's.


The obvious thing about the Ivan's needles is that they a shorter effective length than both the N4MD and N6NC
needles, with a slightly steeper taper angle. The diameter of the staright section is greatly reduced.
So Bolserst's solution, found by trial and error, agrees closely with what Ivan's have been selling!
So now you all know how to get a cheap "Ivan's" jet kit.

Graeme
 

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Discussion Starter #56
Without complicating things overmuch I though some of you would be interested in my findings:
I have just obtained a'spare' bank of carbs to 'play' with, and to install an Ivan's jet jit in.
As I had the carbs apart I took the opportunity to meaure them up (as best I could with a vernier caliper).
My measurements for the stock needles are very similar to Bolserst's findings, plus I have added the dimensions of the Ivans needles.


N4MD (carbs 1 + 4)

Length of parallel section: 16.33
Length of taper section : 30.16
Maximum Diameter : 2.41
Tip Diameter : 1.90


N6NC (carbs 2 + 3)

Length of parallel section: 17.47
Length of taper section : 27.45
Maximum Diameter : 2.42
Tip Diameter : 1.87


Ivans Kit (all carbs)

Length of parallel section: 14.64
Length of taper section : 27.20
Maximum Diameter : 2.38
Tip Diameter : 1.72


The Ivan's kit also uses #105 main jets as opposed to the standard #108's.


The obvious thing about the Ivan's needles is that they a shorter effective length than both the N4MD and N6NC
needles, with a slightly steeper taper angle. The diameter of the staright section is greatly reduced.
So Bolserst's solution, found by trial and error, agrees closely with what Ivan's have been selling!
So now you all know how to get a cheap "Ivan's" jet kit.

Graeme
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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Well its finally falling into place! I think I have gotten alot of the tinkering out of the way now and have found something that works pretty well.
My setup now:

I am still using the new needles (set on 3rd notch/center),
changed the mains to #105's, put about 9 3/8s holes in the airbox and have the mixture screws at 2 turns out.

Results:
It runs really well! It smells a bit rich when its first warming up and when on the choke but after that it smells about the same as my friends GSXR 750 (still a bit gasy but not unbarable). synching the carbs helped alot too:withs:. I did the blip test and the idle is rock solid. It drops right back to 1100 and stays there. The jerkyness when rolling on the throttle is almost nonexistant now and it runs great otherwise. I actually think my clutch is starting to slip a bit now because of how fast it climbs through the rpms. The guy i bought it from a year ago said that he thought it was slipping a bit but I would never notice it because the bike has plenty of power (sort of true sort of not, but I want more:FIREdevil). I havent done enough riding on it yet to see the damage to the fuel milage but ill figure it out as the weather gets better. I still want to get it on the dyno at some point but that may be a while.
 

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Discussion Starter #59
So what are the best options for a stock setup. I don't really want to mess with the stock needles.
As the title of the thread implies, there seems to be quite a bit a variance in how different ZR-7s run with seemingly indentical, or stock carb setups.
So, there isn't any one best setup.

Are you having any particular problems that you are trying to solve?
The most common jetting issue with the ZR-7 is off idle hesitation. If you don't want to mess with the needles, a lot of folks have had found that setting the idle screws to 2 1/2 turns out helps with the hesitation. Others have switched to #38 pilot jets to help richen up the off idle mixture.
 

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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.
 
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