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Discussion Starter · #1 ·
On the way to work today, my C model was acting up. It hasn't been started in about a week. After I started to work, it got really bogged down like it was running out of gas, then died. It would restart after a while of cranking, and would run pretty good, then 2 minutes later the same thing would happen. I got it home, and before I shut it off, it was barely idling and ran like it was only firing on 2 cylinders. I do have gas in the tank, and fuel in the (clear) fuel filter. My guess is ignition. Anyone have any other ideas?
 

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It could be what you are suggesting, but early K bikes also had loads of carb icing issues. It sounds similiar in symptoms to what you are describing.

Is it a little chilly where you live ATM???? The reason it runs OK after sitting, is that the engine heat has melted the iced carbs. Once on the move again, it starts to act up. 1st missing on one, then down to two, eventually stopping completely. Repeat process. I thought the earlier US models had carb heater kits fitted??? But maybe it isn';t this issue at all, but certainly worth investigating.:smile
 

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Maybe the fuel tank vent is pinched? Next time it dies, try to open the fuel cap very fast and if you hear a rush of air entering, you probably found your cause. Maybe not but maybe yes...
 

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Discussion Starter · #4 · (Edited)
Is there a doctor in the house?

I'll check the fuel tank vent, but it was running pretty good before I parked it, other than idle/slow speed issues. There's no chance of the carb icing since it has been in the 60's here. Here's the rest of the symptoms:

BEFORE today - Started right up every time with some choke. There sounds like some mechanical "clunking" in the engine sometimes, but only during starting. Once warmed up, it would backfire occasionally (back through the carbs) at idle, and only did this after it was warmed up. After driving hard for a while, the RPM stays up somewhere around 2,000 to 3,000, then drops off to my idle set at 1,000. When I rev it up it falls back to about 1,500 and then coughs, and drops off to 1,000. BUT when I crack it wide open while driving, this thing [was] a ROCKET. A really scary arm-stretcher!

What I did so far - I took the carbs apart and cleaned them up. I blasted the passages with carb cleaner, they all seemed free and clear. There was a little trash in the bowls, so I replaced the in-line fuel filter. I didn't think the fuel pump would be the problem, since they are usually working or completely dead. I'm at 47,000 miles now, and I checked the valve clearance while I had the carbs off. They are all right on. I also found a massive vacuum leak. The line tapped off #1 and #4 (between the carbs and the head) came to a T fitting, but was disconnected, so I just plugged it. I think it's a California model.

Thanks so much for the input already. I'll be checking this frequently to see if anyone has any more input.
 

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Carb icing can occur if it is high humidity but the weather is not excessively cold. Get a lot of that in the UK which causes icing.

The carb heater pipe has a small inline filter, make sure that is clear if you have the facility.

Fluctuating idle can be caused by an air leak, so finding the loose pipe may have fixed your problems (hopefully)
 

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I had a mate with similiar problems yesterday on his B model call over. Turns out, two of the vaccum lines going to the ram air pods were unhooked. Worth checking too, as it's a no cost fix.:smile
 

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I Have Had That Problem And Found A Couple Of Things One Is The Jet Pin Is Coroted And Letting To Much Fuel In Therefor Fluding The Carbs. So I Replaced The Carbs. Only To Find That My #1 And $ Valve Were Sticking So Check If Mabe You Might Have To Do A Valve Adjust. It Worked For Me. Hope It Works
 

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Discussion Starter · #8 ·
STILL messed up.

Well, I did more digging into it yesterday. The tank is venting fine. The fuel pump and relay work fine. I have spark and air also. I thought it might have jumped timing, since the timing chain was REALLY loose when I bought it. I checked the timing chain/sprockets last night and they were right on. What else do you need for an engine to run? I took it on the road yesterday and it's really bogged down and feels that it only is running on 1 or 2 cylinders. If I crack the throttle wide open, if it doesn't stall, it takes about 3 seconds for the RPMs to attempt to catch up. The valves are adjusted right on. Maybe blown head gasket? Unfortunately I don't have any way to test the compression.

I'm planning to tear down the carbs tonight and see if I find anything obvious. :headscratch

This sucks.
 

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Discussion Starter · #9 ·
New Pics

Well, I tore the carbs down last night and cleaned them up *again*. Nothing looks out of the ordinary. Floats, needles, jets look good. All passages are clear. However, I did find that whoever took the top of the carbs off (upper diaphragm) pinched the diaphragm under the cover when re-assembling. What would this do (I'm not really a carb guy)?

I pulled the head off today. I plan on cleaning up the valves, and maybe lapping them in. The cams appear fine for almost 50,000 miles. Below is a picture of the worst exhaust chamber - #2, and a valve, the pistons, and the bottom of the head. You can see all the other pictures here.







 

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Discussion Starter · #10 ·
Well, here's today's update.
I was lapping the valves today and found a burnt #1 intake valve. It was sunk into the seat and about to get eaten! So that explains the occasional backfiring through the carbs after it got warmed up.

I was also thinking - I jumped the fuel pump off the battery and it worked great, but if the fuel pump relay was intermittent or not working, would the fuel still gravity feed into the carbs and give me about 1 minute of running before it dies?

I hope this is all coming to an end soon. This nice sunny weather is killing me knowing that my ZX-11 is in the garage, "beheaded."
 

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Discussion Starter · #11 ·
Getting closer! Between 6 kids, work, church, and school, I can't seem to squeeze time in to get this thing back together!

Today's update... I installed the new valve, lapped it in - still need to get a shim. The head and cams are reinstalled and torqued. I still have the following parts in my garage awaiting installation (my time):

- Vance & Hines exhaust system from a Honda 750 (here comes some ******* welding) Will I jet the carbs? Maybe. Will it really hurt if I don't?
- New fork seals
- Used clutch and spring set
- New o-ring chain
- Used fuel pump relay
- Looking for a 48-tooth sprocket :thumbup

...must ...get ...sleep. C-'ya later!
 

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I had an issue with my pickup.... only became a problem when warmed up, have a look at chug chug in the 9 thread
 

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Discussion Starter · #13 ·
Doggone it. Now that I've lapped all my valves in, all 16 clearances are out of limits.

16 shims - $5 each. Yuk.

Also, since I'm buying stuff I have no time to install... I just bought a 50-tooth rear sprocket. I hope I didn't go too high. I just don't need to go 176 MPH. I live at 0 to 70.
 

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You will pop mono's like a champ now LOL
 

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Discussion Starter · #15 · (Edited)
Lotsokids said:
...it got really bogged down like it was running out of gas, then died. It would restart after a while of cranking, and would run pretty good, then 2 minutes later the same thing would happen. I got it home, and before I shut it off, it was barely idling and ran like it was only firing on 2 cylinders...
Well, after all this work, I'm back to square 1.:tard

- Replaced the #1 intake valve
- Re-shimmed ALL the valves
- Replaced fuel pump relay
- Fuel pump is good
- Cleaned carbs entirely (second time now)
- New fuel filter
- Sincronized the carbs
- All spark plugs are firing
- Fuel tank is vented

Just now I was checking the carbs, and decided to tie the vacuum on #1 and #4 together and plug the T fitting (does that make sense?) That's how it was when I bought the bike, but the T was not connected to anything causing a huge vacuum leak. As soon as I did this, the idle dropped back down just as it is supposed to (idle was hanging up at 3,000 RPM). I was amazed! So I grabbed my helmet and hit the road... only to push it about 1/4 mile home and threw it in the garage again. Once in the garage, it fired up and ran like new. IT ONLY SEEMS TO RUN IN THE GARAGE.

I thought I was a mechanic, but it looks like I'll be taking this thing to the shop. :angry
 

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i have this same problem..['87 zx1000]...i see you no. 1 combustion area has more carbon build up than the others.....same with mine....i think your rubber tips on the float needles are old ,even if they look good,and don't seat well.....this is what i need....i clean the carbs,but they still let gas go up into the carbs and down into the cylinder pooling up around the piston....then when you start up the bike it coats the piston and plugs with carbon ....fouling them out.....and think after i ride down the road ,which the most i can go, is about 3 grand....after a mile it starts to be able to rev up and all cylinders are firing....i think this is because the motor heats up and burns the plugs on the fouled firing cylinders ,up high enough ,that they start firing again.....and it will run good at steady highway speeds...but as soon as i have to idle again....the float needles that are stuck...start flowing more gas than the bike is using[at low rpms] than the plugs foul...and i open the trottle all the way and it hesitates 3 seconds[like on your bike] than i hauls ass....lol.

i was thinking the same thing about a burnt valve....but one carb cleaning job...the bike started up cold...and rode fine.....which i should not of done if its was the valve only causing the problem.....but i've had leaking float needles before....and it ran rough but not the same as this.

a few years ago i had one of my pick up coils go bad[have two on mine 1/4 and 2/3] it ran good but at aroud 5 grand a couple cylinders stoped firing...replaced and was good.

i was thinking maybe i was getting enough spark at higher rpm to get a clean burn....but it runs ok after awhile....but i did make sure my coil wires where seating good in the boots and coils.....did this yesterday,but still problem.......i still need to buy new float needle's.....

also....i think[maybe] why the NO. 1 piston gets more carbon build up....is because after you stop and park the bike...it is leaning to the left if its on the kickstand and just alittle more gas gets to that carb.....gas comes in the middle of carbs....even when fuel pump is not putting more in[don't have fuel pump on mine ,but i think it still lets it leak from petcock,so i put a on/of valve inline,i think the suction keeps it from draing]...theres still some fuel left from pump to carbs...if no. 1 carb is leaking,it will leak more than the others....considering all where having a leaking float needle....no. 1 piston would see alittle gas pooling up...and then the starter is hit...and bam,it fouls.....and coats the piston/plug with carbon.....and my no.1 cylinder head and plugs have more build up than others....sometimes i've taken the plugs out and no.1 is wet with gas and carbon.

i'm still investigating.....so please post back Lotsokids on what you find.....also , i'm going to link this thread over at the concours.org forum...and see what they think.....i've had alot of help there....this is getting to be a bitch...and i want my bike to run good again :)
 

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Discussion Starter · #17 · (Edited)
ENGINE IS DESTROYED

Today I replaced the air filter (K&N). I just took it out a few minutes ago, and when I hit second gear (not too aggressively) there was a loud BANG and what sounded like metal scrambling around in the engine. No oil leaks or holes, so who knows? I thought the timing chain broke, but it is still in tact. The crank shaft will rotate some, but locks up in a certain position (valve/piston interference?).

DOGGONE IT!!! so my 3 options are:

1. Spend $1,700 on a used engine
2. Sell the bike whole and not running
3. Part it out
 

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you should find a used motor for no more than 1000.....or just by the parts used to rebuild around 600.....maybe just the bottom end.

or sell it/part out and put that money towards a good shape one....if you don't want to rebuild it.
 

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Discussion Starter · #19 ·
Well, I bought an engine Monday, it's in the mail. I got it off Ebay, used - $253 including shipping. The engine has no guts, but seller says it has good crank, rods, pistons, and complete head. I still haven't torn into mine yet.

I'm dumping a lot of money into this thing - WAY more than it's worth.

More to follow... :angry
 

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Discussion Starter · #20 · (Edited)
Well, I tore into it some today. After removing the sparkplugs, I saw all the pistons moving freely up and down with no binding at all. This was done after I removed the timing chain. SO... that leads me to the cams and timing chain. It is evident that the timing chain jumped some teeth. The bottom retainer plate is tore up with chunks of it still lodged in the chain itself. Even with the chain disconnected at the bottom, the cams are binding up somehow. I even put break-in lube on them when I put it all together. I had this all set up according to the manual when I put it together. I just bought this engine which should be here in a couple days. I'll probably replace the cams and timing chain (or maybe the whole head) since I have so much labor into lapping all 16 valves in and cleaning them up.

So this is good news... I really didn't want to tear that engine down.

With the timing chain disconnected, I can rotate the engine all the way around. I thought these engines were interference engines?
 
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