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Discussion Starter #1
Hi All,

I recently purchased a Canadian 1984 ZN-1100 LTD Shaft in non-running condition. I have been slowly working away on restoring it to running condition. From what I can tell, the bike is mostly stock and still has the original airbox which I will definitely keep.

While rebuilding the carbs, I have come across some interesting (strange) jetting and am turning to this forum for advice/input.

First off, what I found strange was that the main jets for cylinders 1 & 4 are not the same as for cylinders 2 & 3. However, the Kawasaki Service Manual (supplement for the ZN) shows that this is correct. The middle two cylinders use #127.5 main jets while the outer cylinders use #122.5 jets. I had never seen this before, and this is unique to the ZN because the same manual states that the KZ-1100 uses #120 for all 4 of its main jets.

Can anyone offer an explanation as to why the ZN gets this arrangement for its main jets? I thought the ZN shaft and KZ shaft shared the same engine and same carbs, so why the difference in jetting?

More importantly, should I look to change the jetting? I live at sea level and have read on this site that a #130 jet might be more appropriate for my altitude.

But the real shocker was when I discovered that my bike came with #25 pilot jets in all carbs. The service manual and all info I have found on the internet indicates that the pilot jets should be #37.5. My service manual indicates that the KZ-1100 and ZN-1100 all used #37.5 including the California models.

Can anyone offer an explanation of why my bike came with such small pilot jets? I am thinking I should definitely swap these out for the #37.5 jets.

The final surprise was that my bike came a California Jet Needles 5C48 when the normal needle is 5C50. Should I change these?

Does anyone have their carb jetting specs that they can share? I am interested in what came as stock, and what mods may have helped when using the stock airbox. Thanks for any help you can provide.
 

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My guess is that the center cylinders are jetted a little richer because they run hotter than the outside cylinders. Going richer on the jet sizes doesn't necessarily mean more hp. In fact the opposite is normally true. Nascar engine builders go lean until the pistons burn and then richen them up a bit. When emissions became a concern, tuning lean meant less unburned hydrocarbons coming out the exhaust but more nitric oxides so car engines are tuned for 14.7 air fuel ratio which is a compromise setting.

I didn't bother to look at the jet sizes on my ZN700. It runs well and gets 50mpg on the highway and 40 around town which is ok with me.
 

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Discussion Starter #3
Thanks RoadRunner. I think your theory is correct about the middle two cylinders but that does not explain why the KZ-1100 was not treated the same way. Not that that is the main issue here; it is just an item of curiosity. My hope is that others with ZN's will find this post and add their carb specs here. So far I have not found anyone who uses anything other than the stock 37.5 pilot jet so I think we can safely say that is correct and I have them on order.
So this is mainly about the mains and the needles.
 

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Send Hoyt Clagwell, a forum member, a message and he might can help. He has a ZN1100 that he rebuilt the engine so he should be fairly familiar with the bike.
 

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I know everybody says the reasons for the two center cylinders having richer jetting is because they get hotter, but according to Factory Pro, which makes carburetors kits for motorcycles, ….and of course has testing equipment..........the reasons for the richer jets on the two inboard cylinders is simply because their air intake tracks are shorter and straighter than the two outboards, thus they get better air density ...am only saying what they state.
 

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Discussion Starter #6
I will reach out to Hoyt, thanks RoadRunner. The reason provided by Hugojose makes sense but again I come back to this: Why is the jetting for the KZ1100 not done the same way? Surely the KZ1100 shaft and the ZN1100 shaft of the same year share the same carbs and engines. Therefore I would expect them to have the same jetting but they don't. The KZ uses the same main jets on all 4 cylinders. Maybe Hoyt can share some light on this.
 

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Hey WFO-KZ,
To tell you the truth I never noticed that the ZN1100 had different main jets for the 2 & 3 cylinders. I've had the carbs apart several times for cleaning and didn't notice. I'll have to dig out my service manual and ZN1100 supplement to confirm if that is indeed the case. If so, The only reason I can think of would have to do with the different (Jardin?) exhaust pipes. I'll try to confirm that the jets are in fact different for different cylinders and get back to you later.
All the best,
Hoyt
P.S I don't know if forum member wiredgeorge is still posting here. He is the best carb man that I know of.

P.P.S. After rebuilding the top end and installing dyna coils my bike has been running fantastic! Perhaps slightly rich. I'm at 1,600 feet above sea level and have ridden along the seashore as well as the Blue Ridge Pkwy and the bike ran great throughout.
 

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Queasy Rider
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OK, I just checked. You are correct sir. The #1 & 4 carbs have 122.5 mains and the #2 & 3 have 127.5
Like I said, I'm running stock jetting and airbox (with a Uni foam filter) and the bike runs great. It is running slightly rich but I suspect that is a pilot screw adjustment.or maybe I should raise up the jet needles a notch. If I remember correctly, they're on the middle of 5 notches now.
It's a great bike. I've got 150,000kms (93,000 miles) on it and it's been very dependable. One thing that I should have done years ago was to swap out the bars. I recently installed "Steve McQueen" style bars from Dime City Cycles and the bike is so much more fun to ride.
 

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Discussion Starter #9
Thank you Hoyt,
I cannot wait to get it fired up and experience it for myself. I have never tried a ZN and am looking forward to it. I have heard from owners like yourself that they really love this bike and that the bars need to be swapped out. For the carbs, I have been doing some research on Partzilla and my service manual. My assumptions were wrong! The ZN and KZ do NOT share the same carbs. I am unsure what the difference is but I think it has to do with the vacuum hoses. On the ZN carb 1 and 4 are connected to each other and nothing else, while carbs 2&3 supply vacuum for the petcock. Maybe that explains why the diffrent jets for 2&3.
 

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Queasy Rider
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WFO-KZ, Two mods that I was really happy with are Dyna coils plus copper core wires and cartridge emulators for the forks from Racetech. I appreciate those emulators every time I ride the bike. The stock forks, as most forks of the era, are soft and mushy on a smooth surface and then become bone jarringly hard when encountering a pothole. With emulators they are nice and firm on a smooth surface then give smoothly when hitting a bump. Here's a link to a post I did about them years ago. You won't regret it if you decide to install them.
 

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Discussion Starter #11
I will certainly look into it. I have read that the ignition coils are weak so that may be my first upgrade and handlebars also. Do you have the part number for the bars you used and was there any issues with getting them to fit?
 

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Queasy Rider
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Here's a link to the handle bars that I installed last year. I really love them and they have given me the confidence to add a few degrees to my lean angle. They fit easily but there is going to be some extra length left over on your cables and you will have to carefully position your master cylinder to get it as close to level as possible. The extra cable length is not a big deal for me. If it were summer, I'd post a photo of what the bars look like. Unfortunately, I haven't taken any photos of the bike with the new bars.
 
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