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Discussion Starter · #1 · (Edited)
Joined to search for zn1100 information. The bike has about 4,000 miles and I just cleaned and set the carbs. It actually had one main jet packed with black sludge chunks. First time I had a main fully blocked. The idle jets looked like they had float needle tips poking out of them lol. The throttle plates looked perfectly bench or factory synced. (Plates bisect first hole) I did not check with my gauges. Idle mix screws 2 2.5 2.5 2. Started right up once I put the cdi ground back on lol. Idles and revs flawless and sounds extremely healthy excluding a quiet/soft slap or clash noise that seems to be coming from the middle of the engine case at random times during the brief period I let it idle. I revved a few times to 4,000 rpms and didn't notice the noise or anything else bad. Reminds me of random and soft tappet noises in a random pattern but it's slightly louder and not coming from the top of the engine.. I don't think. If anyone has any guesses or had a similar situation and discovered the cause please share with me. Maybe I didn't tighten the intake rubbers enough? I feel like it would have a lean symptom somewhere in the rev range if that was the case and not a soft split second starter clash noise at random times during idle. Who knows maybe it would go away with an oil change and running the bike. It's the first time it was run in unknown amount of years and it was less than 1 minute of runtime.

I can't really ride it because the tires are old as hell with fault lines for dry rot cracks and loses air. Someone put a derp seat on it but I ordered a factory one to recover that's not rotted out. It's beat up and had one hole drilled into the frame to secure the seat. Looks like it came off a junkyard bike but the rest of the bike is clean. It needs to go.

Did the carbs come with the idle mixture screws uncovered because as far as I know that would be unusual. All jets were stock and in the correct carbs. Sorry for the long intro post Im just hoping I can get some good news. I'm a little worried about this noise. The bike was last owned by an older gentleman that unfortunately had a leg amputated and then later passed away. His family put the bike away until I bought it for $250 in non operational condition. Tried but didn't start off ether when I picked it up. Either way I'm happy to be the next owner of this motorcycle and hope I can ride it without it suddenly grenading on me causing wreck or something.
 

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Discussion Starter · #3 ·
Welcome aboard. Edit: I would definitely investigate that noise. Good buy at $250
Yes I will keep searching here for similar issues that were fixed. The only one I found so far was a member that said they replaced the bolts that hold the starter clutch together I think. If that's the case yikes because idk if I can do that but they made it sound easy. It's like the engine is lightly stubbing it's toe at random times during idle from cold start. Sort of like a sudden lean spit/cough that some bikes do when they have tears in the intake rubbers. I had one that had lean idle "sneezes" and couldn't figure it out. Eventually they got worse until it started bogging then transitioning to a huge explosion in the exhaust that sounded like a cannon and would actually feel like the bike was kicked from behind. It would hit 7,000rpm, bog then have a sudden explosion in exhaust. It was torn up intake rubbers on a bandit 1200. The rubbers on this zn1100 have no tears though. The way the engine acts is similar but it's like a split second starter clash. But not a full clash it's like a glancing skip clash noise that breaks the smooth idle of the engine for a split second then it carries on. I will check more stuff tomorrow I guess. For the money I guess it's still not any big loss at this point. I could try to post a picture but it's not like it's a special or modified so I just say it's clean.
 

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Welcome to the forums Kowl.

I too have a ZN1100 but you got a better deal on it than me. I paid $500 Canadian so around $400 US.
I had to rebuild half of the wiring harness but it now runs and has been ridden for the last two years.

The noise from middle of engine is likely cam chain noise. You might want to remove and lubricate the cam chain adjuster.

It does not idle as smoothly as I would like, so we may be able to help each other.

One odd thing about our ZN's that you probably noticed and that is that the middle two carbs use a different main jet than the outer two carbs.

Have you checked/set the valve clearances yet? How is the compression?

To answer your question, the pilot air screw did come with an aluminum plug. If you want removable, 3D printed plugs you can download them for free from thingiverse.

Here is one that I designed that uses an o-ring


Here is one that I designed that uses a snap-fit

I think these plugs will fit most of the Kawi big fours of that era.
 

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Discussion Starter · #5 ·
Old thread I mentioned.
Welcome to the forums Kowl.

I too have a ZN1100 but you got a better deal on it than me. I paid $500 Canadian so around $400 US.
I had to rebuild half of the wiring harness but it now runs and has been ridden for the last two years.

The noise from middle of engine is likely cam chain noise. You might want to remove and lubricate the cam chain adjuster.

It does not idle as smoothly as I would like, so we may be able to help each other.

One odd thing about our ZN's that you probably noticed and that is that the middle two carbs use a different main jet than the outer two carbs.

Have you checked/set the valve clearances yet? How is the compression?

To answer your question, the pilot air screw did come with an aluminum plug. If you want removable, 3D printed plugs you can download them for free from thingiverse.

Here is one that I designed that uses an o-ring


Here is one that I designed that uses a snap-fit

I think these plugs will fit most of the Kawi big fours of that era.
Thanks for this reply. I figured somebody played with the carb because those plugs were gone. They were all at two turns out so I increased the middle two half a turn. Yes I saw the etching in the jets and saw it was different. It was odd to me. This bike only has 3132 miles actually. I have not checked compression but it does fire over easily in like less than one crank now. But you think the noise is a stuck cam chain adjuster rod or something? The noise is only at idle and it literally acts like the engine got paused for a millisecond then continues on idling perfectly. At least that's what I think. I have cleaned and refurbished lots of side and downdraft carbs and cable too. If your idle mix screws are damaged at all it will be a constant fight to idle well. Same with petcock. The sellers were actually kind enough toail me a title signed over to me by a POA. I bought it without the title but now have a plate for it. **** the tires and have to go over the brakes.
 

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I would definitely check compression and set the valves before you go too much further Also I would remove and lube the adjuster.

The engine stumble would exacerbate any cam chain noise in my opinion.

I have yet to fiddle with the pilot air screws because it's just not high on my priority list yet.

Wheel Tire Fuel tank Automotive fuel system Vehicle
 

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Discussion Starter · #7 ·
I can tell these things are good cruising bikes without even riding one yet myself lol. But STUMBLE. That's it, that's exactly what it was but so slight and fast that most people wouldn't even notice it. I started it this morning and it took full choke. Went to half after 30 seconds and then about another 10 seconds pushed it all the way in. Remember I only ran the bike for like 1 minute after cleaning them and didn't even adjust idle stop speed. It idled high around 1500 then I let it warm a second like that and backed the idle screw out til it ran nice at 1100 rpm. Idk what it's supposed to be but it ran better and the stumble was just about gone. The bike started to warm up and smell like pest bleh but am used to this with old sitters. So what's going on now is what sounds like a soft tappet noise in #4. Is video posting possible?

But yeah those low speed mix screws won't really look all that damaged til you put them under a loop like 40x magnification. Then you'll see they bend and have badly worn tips. I have an 89zx600 with this, a bad petcock and another mf of a problem I haven't diagnosed yet. But when I run it the thing rips like a mf but won't idle for sh1t. Also doesn't help that it has mains bigger than most 1000cc cruisers of the era. Over carb'd old straight pipe and pods. That's how I got it So it idles like crap and I constantly have to blip it to keep it idling right. It was actually running on 3 cylinders when I bought it lmao it ran and only has about 8,000 miles. I get these cheap bikes that once I get running usually have other problems that I won't tackle for years. But also check your tank vent circuit and cap. They may have partial clogs that once your spray out could help your idle. If you've checked the harder stuff like gaps, timing and compression then idk it must be something easier. Like leaving a cdi ground wire off after cleaning carbs and wondering what you did wrong.
 

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Discussion Starter · #8 ·
I think that stumble was a cold engine stumble because it would only happen at idle with no choke or throttling. Seems I might have just been closing the enrichment circuit a little too soon and it would idle higher at 1500rpms because the idle speed needed lowering. Since lowering the idle speed and warming it up one more time to change the oil and filter the stumble had disappeared. It does have soft top end noise though. Sometimes a few soft clicks from what sounds like the #4 and sometimes a couple from the #1. It doesn't sound bad I guess but i do notice a couple light ticks in random patterns that are pronounced when listening to the engine run. I guess I will have to check the valves and tensioner. Then probably clean and polish up the brakes with a flush and bleed since they drag slightly. The fluid looks low and evaporated.
 

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When I had my carbs apart, all jets etc were put under a digital microscope at various magnifications. Here is one screen capture of the tip of one of my pilot air screws. Note however, that Kawi parts listing call this a pilot air screw but I believe based on its location on the cylinder head side of the carb, and its shape that it is actually a pilot fuel screw. Any comments?

Natural material Metal Wood Steel Titanium
 

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Glad to hear your stumble is almost gone. I have checked the gas tank vent on mine and its good. It came with oversize pilot jets and I switched them back to OEM size. I wonder if that was a mistake.

Keep us posted on your valve clearance check.
 

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Discussion Starter · #11 · (Edited)
Glad to hear your stumble is almost gone. I have checked the gas tank vent on mine and its good. It came with oversize pilot jets and I switched them back to OEM size. I wonder if that was a mistake.

Keep us posted on your valve clearance check.
That looks like it should be working fine and yes when it's on the cylinder side it's almost always a fuel screw. All the quads and dirt bikes I ever touched were that way but they were all old so yeah lol. I would go back to the idle jets you had if they worked better. If it has any air flow mods I'm sure you considered that's why they were increased. In the carbs there's tiny idle circuit holes that are super hard to clean. They need a long dip or super Sonic clean when a steel, high e guitar string won't do the job. Maybe those are partially blocked. And I'm guessing you probably had them dynamic or bench synced. Maybe it's not even a fuel issue but it probably has to do with the stock size jets.

But yeah that stumble was just a cold engine stumble I think. It doesn't do it now. I guess the low miles and well cleaned carbs helped it run when it really should've needed enrichment a little longer. It runs like an old new bike but just has some random top end clicks I think I only hear coming from the far left and right top of the engine. Of the videos I've watched of people running their bikes with the same engine I've noticed they have a very similar sounding clickyness but it's actually louder than what I'm hearing on mine. I'm less concerned now and think it's normal operation noises but will still check. To be honest I'm a little lazy about it since it's low mileage and really doesn't seem like it was whipped on for 3000 miles. Only valves I ever touched were my first bike an 86 450 night hawk and small engines. Honestly didn't even need it the bike had about 4000 miles and I was just trying to learn. That was 11 years ago and the gauges are long gone now lol. I don't want to pop that cap off being neurotic about every little tick. It actually does remind me of the 450 and 750 nighthawk I had at the time speaking of valve noise. Maybe I should just do the tires and brakes then run it around gently for a bit and see what happens. I'm a lot less worried that I cleaned the carbs on an old damaged bike now. Seats coming tires are coming and I really want to try it out lol. All the bikes I've had since then were bucket shim ones in good shape or had loud exhausts so maybe I just forgot how these can sound clicky. I have read that they aren't ever silent so maybe I'm just too worried 😅 my non expert carb advice would be to go back up 1 size with slow jets. Usually it's two up main, one up slow with old carb'd bikes when you want more power stock or with airbox and exhaust mods. Here was the main jet that clogged and 1 of 4 slow jets clogged. Imagine how hard it is to clean old, dry, solid deposits from the tiny idle circuit passageways.
 

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I have a ZN700 that I bought with 1,052 miles on it. At 6,000 miles the valve adjustment was way off with a couple valves having zero clearance. So, I suggest you adjust the valves. The noise you are hearing, I also suspect the cam chain is too loose. My bike has the automatic adjustment and I assume yours does too. I have read that the springs in the auto adjustment device gets weak over time and need replacement. Here is a video on adjusting the valves on a 750 which may be the same as your bike that you may learn a few tips. One thing they recommend is roughing up the surface on one part that may keep the chain from loosening.
 

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Discussion Starter · #13 ·
Aw t!ties they're bucket shims. I thought they went longer without needing adjustment if they aren't whipped on all the time. I think the 750 nighthawk I had was too actually but it ran super quiet. Shouldn't have let that go. So when these are making noises it's because they could use new shims and when the other kind is a little noisy that's usually normal operation right? Well I don't have to take the cams out to check at least but by the way you make it sound I'll probably be getting new shims and end up needing to do it and reset the timing. So I guess I'm convinced to at least check before riding it. Don't want to ruin any valves. Thank you for the video this one seems like the better of the ones that are out there

I bought a couple gs1000's and one had higher mileage and a steady cam chain tick that increased with revs. I turned it's adjuster bolt in a quarter turn (max I believe) and it almost disappeared. But I don't have a noise like that. I could still check it though because I appreciate your concern and the problem you're talking about when they sit. It's easy enough. The stumble was the first time I ran it after cleaning the carbs and I only ran it for about 1 minute. Used full and half choke for like 30 seconds max then it idled at 1500rpms and would have a split second idle stumble every couple seconds like a "flinch" or something then went away when warm. It doesn't do it now when I warmed it up again to change oil and filter. And once for two minutes to set the idle down lower. I think it was just a cold engine with no choke? But I haven't ridden it just ran it for two minutes to do that stuff. I sold a bandit 1200 to a guy and 10,000 miles later the engine is super ticky and clicky on top all the time on each cylinder but was super smooth when I sold it to him at 20,000 miles and they're bucket shim too I believe. I shouldn't have let that one go either lol.
 

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Time for some clarification. Most Kawis use buckets. Some use "Shim Under the Bucket" (needs camshaft removal to swap shims) and some use "Shim On Top of Bucket" (cams do not need removal).

The ZN700 uses Shim Under the Bucket while the ZN1100 uses Shim On Top of Bucket.

In both cases, it is very easy to check the clearance. Changing the clearance is much harder on the 700 than on the 1100 so in that sense Kowl, you are in luck.

Roadrunner322's advice is solid. With the low mileage on your ZN1100 it is entirely possible that it has NEVER had a valve clearance check and adjust. On any new bike, this is a critical maintenance item because during break in, the valves will seat themselves and this causes clearance to get tighter which can lead to burnt valves, burnt valve seats and loss of compression.
 

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I wish I knew why the pilot jets on mine were not stock size and I also wish I knew what it ran like with the bigger jets but I bought it as a basket case and since there were no pods and since exhaust was stock, I decided to put it back to stock jet sizes.

I have not done a carb synch, but I also never separated the carbs and visually they look perfect. I also believe every carb passageway was clean, but if I end up removing the carbs I will of course clean them again.

But simplest things first. I will play with the pilot fuel screw and possibly buy new fuel screws.
 

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Discussion Starter · #16 · (Edited)
Time for some clarification. Most Kawis use buckets. Some use "Shim Under the Bucket" (needs camshaft removal to swap shims) and some use "Shim On Top of Bucket" (cams do not need removal).

The ZN700 uses Shim Under the Bucket while the ZN1100 uses Shim On Top of Bucket.

In both cases, it is very easy to check the clearance. Changing the clearance is much harder on the 700 than on the 1100 so in that sense Kowl, you are in luck.

Roadrunner322's advice is solid. With the low mileage on your ZN1100 it is entirely possible that it has NEVER had a valve clearance check and adjust. On any new bike, this is a critical maintenance item because during break in, the valves will seat themselves and this causes clearance to get tighter which can lead to burnt valves, burnt valve seats and loss of compression.
Hooray for me I actually got off easy then 😆 but seriously thanks for this response I promise I'll get gauges and check because of the clarification and good advice from the forum.

As far as the idle goes that's what I would've done too. I also bench sync with a tiny drill bit or piece of steel skinny guitar string CAREFULLY so I don't ruin the plate edges. Then set the idle. I haven't used my vacuum gauges yet.
 

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Discussion Starter · #18 ·
Here are two common tools used to change shims on the big fours that use shims on top of bucket.
I would be interested in feedback from those who have used the pry bar style in the first link, as I have only used the factory tool shown in the 2nd link.


Hm I would probably use the second on as well and this will be a good reference in case I need it thanks.
 

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Personally, I won't buy a bike with nder bucket valve shims. Too much time in valve adjustment. The ZZR1200 has a very easy valve shim system, you just slide the rocker over, after measuring the gap, no special tools. My Suzuki GS750ES has a cam follower rocker arm. That is so easy to adjust, just loosen the locknut and adjust the screw, 4 valves per cylinder, really easy, and I can easily get 3500 miles between checking them. The Suzuki has 42K miles on it, and the valves have not changed their adjustment the last two times I checked them. The ZZR1200 I haven't had to touch yet. :)
 

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I have to wonder at the wisdom of engineers when they decided it was a good idea to require removal of both cams just to do a shim swaps. The inherent danger of getting the valve timing wrong and the resulting mangled valves is a huge risk item.

Conversely, it is true that an occasional shim has been "spit out" on shim on top designs, this was rare and usually due to loose clearance and over-revving the engine.

The good old fashioned "rocker style" that Kawasakian mentioned was indeed the simplest and fastest to adjust.
If it was good enough for many Porsche engines, it should be good enough for all of us.
 
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