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Discussion Starter #1
Alright,

I'll start off by saying that the ZR7 modifications are complete. Everything is functionnal, put new carbs in the bike to replace the troublesome old carbs that were repaired without much knowledge it seems by a previous owner.

I cleaned every orifice in the new carbs, they are speckling clean and air was blown thru jets and body passages, every oring is clean and fresh, slides go up and down flawlessly, float level was checked with a caliper and they are all within spec, the float needles don't have a ring in the rubber part due to wear, the little button on them press in and out normally, jets are stock and the correct size as stamped on them, diaphragms are without punctures and ripples

Now, for the issue:

I put new NGK DR9EA plugs in (gapped and all).

The bike runs real harsh while warming up. It feels like an intake leak, The boots from carb to cylinder head were cracked on the outside, I pulled them out and they weren
't cracked all the way through but I sealed the cracks anyway just to be diligent.

I suspected a leak from the airbox to carb boots so I used zip-ties to keep the closed along sith the spring (one beside the other) but to no avail.

I am now suspecting an exhaust manifold leak as I had removed the header before to sandblast the manifold seal collars. I sanded then on the sealing side a bit to have a nice flat surface to press against the copper donut seals.

When warmed up, the bike sounds ok, It might need a carb sync and valve adjustment, revs hang and very slowly go back to idle and are a bit sporadic at idle (maybe 100 to 200 rpms up and down).

When checking the plugs with pilot screw at 1 3/4 turns out, the #2 and #3 cylinders look very lean and the #1 and #4 were a tad rich.

Spark plug caps are brand new NGK caps with the correct OHM resistance.

It ran fine last summer aside from hard cold and slightly warm starting issues.

A Alpha moto carb sync gauge kit and new collars and manifold seals are on the way.

Is there anything I could have overlooked? I'm truly out of ideas. I don't have a huge working space as I live in a small appartment in town with inside parking but I can get away with some oil spills and mechanical work.

Riding season is starting and I'd like not to spend it hunting down gremlins :cry:
 

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Could be a lot of things, but how are the coils, the leads, and the connection between the leads and spark plug caps?
 

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Discussion Starter #3
thank you for your answer Doug,

All connections seem good, I get good spark at every plug,

I changed the exhaust manifold gaskets recently, it does feel better now, but I feel like the bike knocks a little when warming up and riding.

it seems quite happy between 1 1/2 and 1 3/4 turns out for idle. When warm, the revs go back down normally, I suspect that the valves may be out of adjustment and that one may be at .000 and let air in, making an ''intake leak'' at the valve, might explain the knocking as well...

Just have to adjust valves and see for myself, previous owner thought oil had to be filled with the bike on the kickstand so I'm pretty sur it would part of the issue

If you think of anything, please let me know
 

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Discussion Starter #4
alright so a month later, I just finished reassembling the bike after valve adjustment.

It fired pretty quickly, I tightened every boot, re torqued collars on the ex manifold, re torqued plugs etc.

It seems to have some rev hang when warming up, it also feels like it is running on less than 4 cylinders when warming up but after a bit of smooth riding it bangs on all 4.

I put every carb pilot back to 1.5 turns to re establish a base after the valve adjustment.

every once in a while it feels like it gets a little knock coming from somewhere in the engine but when it turned by hand, i could not hear any clanking that a crack journal could cause...

There is some oil on the threads of the #2 plugs...not sure what to do of it
 

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How you know there is no vacuum leak?? Does it have the Kleen system? Did you check the carburators float level with a clear u-tube?? it can be done with the carbs on bike. If you have oil on spark plug, it can be piston rings, (not likely), but could also be valve stem oil seal (likely)
 

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Discussion Starter #6
I havent checked fuel level with the clear tube, I don't have any on hand of the right size and the quarantine makes it a pain to get anything in store. I did get them all to spec on the bench with the float height and a caliper. Will check level with a tube when I can. Bike has the Kleen system but it will stay on because it helps reduced the gas smell and I like to start the bike inside because of the slight incline of the garage floor.

I rechecked the plugs, the oil on the plug is from an oil spill i made when adding oil on the cams and journals, no more oil on the thread. I tested for vaccuum leaks and found a little crack on the vaccum tube from the petcock. plugged it and it helped somewhat, new tube will be installed.

When I swapped carbs previously (see older post), i swapped the k trics sensors. I hadn't thought about it until yesterday and I just rotated the sensor counterclockwise some and the bike ran noticeably better. Maybe this is the culprit. There is a difference in the running condition of the thing when it is plugged and unplugged.

I'll try emptying the gas tank and putting 94 octane in it as other gas ratings have higher ethanol contents than previously. I'll adjust the k tric then without fear for pinging. The knock i'm getting might be pinging but i have never experienced it before.

Also along with the k tric ''adjustment'', rev hang is almost completely gone. That's quite weird... Temperature outside is 14 celsius, same as yesterday...(57 Fahreneit)
 

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I asked about the Kleen system because it is another source of vacuum leaks. Leave it in place and you are reducing your footprint on the damage we are inflicting on the planet. I greatly admire your decision leaving it on.

The K sensors are really throttle position sensors, giving this information to the ignitor. It looks you are sorting this thing out. Running on less than 4 when cold seems to be a symptom of being too lean.
 

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Discussion Starter #8
Thank you, even though it makes the bike a little more complicated, it is really still dead simple, keep the flaps clean and it works fine, I hate walking near the woods and hearing a bike roar and leaving an intense hydrocarbon smell, the zr being air cooled makes it smellier.

I have a love/hate relationship with mechanical smells, love em when wrenching, hate em when in traffic or riding. I used to come back home stinking like fuel on my Ninja 500

The k-tric adjusts ignition timing according to throttle position yes, it also determines advance or retardation from base timing, I don't know if when maladjusted it could cause so much retardation that it becomes a detriment to the good running condition of the bike...

I'll keep you guys posted but so far K-tric and general adjustments according to the manual seems to help
 

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Discussion Starter #9
I posted a video for you guys to see.

I only bought the bike last year at the end of the season and I am not sure if this is just a common thing on aircooled 4's or if it is an issue to be adressed. Doesn't feel all that great to me.

Carb sync hasn't been done yet but they don't feel that much out of sync. Would it help?

The third clip shows the audible knock and the rpm drop at 2:02 . bike was warmed up for about 3-4 minutes and is not running with the choke on.

does any of your bikes do that? I need some reassuring here :oops:. I did the valve adjustment because of this exact thing, Thinking valves were being slapped by the piston at cold temps. Temperature outside is still 14 degrees Celsius. (57F)

 

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Thanks for the video (well more the audio.) That sounds about right as per mine when warming up.
 

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The carb synchronization is basically equalizing the butterflies opening an all carbs, by reading the vacuum produced by the engine thru them. It mostly helps at idle and low rpms, not much at high rpms. You could have eyeballed that before installing the carbs. I'd try first going two turns on the mix screws,..in the US the manual says 1 3/4 and is conservative on the lean side for emission testing. I'd also make sure all the bowl levels are at the seam of the carbs. Other than changing jets, these are all the adjustments you can make.
 

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Discussion Starter #12 (Edited)
Alright Hugo, I'll try all this when I can and report back

And Obo, you bike does give some knocks when warming up? If so I will stop worrying about it and just ride it as it is. It sound right if not for that one thing. Grandfather told to not worry about any issues it might seem to have when cold.

Edit 1: All 4 carb bowl fuel levels are within spec

Edit 2: at 2 turns out, The "knocking" is much less apparent than it used to be, will try at 2 1/2 tomorrow
 

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.....If you have not synch the carbs, you should probably do that now....that is basic, .....but many moons ago before you were born, in this forum (old style), there was a 'partial' carb kit running around.. Mainly, a change to 38 pilot jet(instead of 35), and some washer under the needles. These was said to cure some flat curve, or hesitation, on the ZR-7. I don't have the ZR-7 but the predecessor in the KZ750 line; the Zephyr 750.

........basically, the kit made it richer. I don't think you would need the washers, but the switch to 38 might help, that is idle and low rpms. I run the 38 in my Zeph instead of the 35. Before I did, I had to open the mix screws almost 3 1/2 turns (from the manual 2 1/2) to make it run better at low rpms. Bikes are simply too lean from factory to meet stringent emissions tests.
 

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Discussion Starter #14 (Edited)
I'll try what I can before getting on to use a jet kit but if it comes to that I'll do the switch.

I have taken out the spark plugs after a short ride of about 10 minutes, with mild throttle input, not above 4k rpm. Bike definitely felt better than it used to but there still that little knock every now and again. Wondering if #2 cylinder could be missing (1 to 4 from left to right)

Edit 1: Choke plunger on carb for cyl 2 is wet. Will take carb out to swap carb plungers with spare parts
 

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I am lost. The plunger is the enrichener on the side ("choke"). To get it out, you would have to get the carbs out and then separate them. How can you now is wet, and in any case, this is only for start up when cold.. Are you talking about #2 spark plug??
 

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Discussion Starter #16 (Edited)
It is wet on the outside, I believe this part is supposed to be sealed and no fuel should be going out from inside the carb to have the enricher slide be wet on the outside where the link between the 4 chokes attaches to.

I saw it when looking at the carb while on the bike.

I am suggesting that somehow it might be leaking from that part, which seems unusual, if fuel gets out, air might be going in. Cylinder #2 looks like it might be misfiring so culprit could be this. I would like to have a second opinion on the state of the plugs, I don't trust my knowledge that much.
 

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One trick to get the butterflies opening simultaneously is to place a small ball bearing in each carb. adjust the screws so that all 4 bearings drop at the same time as you open the butterflies.
Anilv
 

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Discussion Starter #19
As many carbe'd bike thing, I undid the carb yesterday yet again to inspect choke plugers and some of em were pretty scoured so I switched them with other I had in spare parts and made sur everything was tight. I also recleaned the pilot jets. Bike is up and running, no more knocks, did about 300KMs since then and doesn't take up oil, it ran truly marvelously (up to redline shall I add 🧐 🧐 )

Thank you for everyone's time on this thread. Bike works better than it ever did.

Could not be happier.

PS: I have been told by a long timer that the knocking I experienced could be due to the clutch and that it was totally normal for this kind of aircooled 4.
 
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