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kz440 LTD D1 1983
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Discussion Starter · #1 ·
So i've bought this bike for cheap since it was not running well, the person i bought it from said it just randomly one day did not want to go above 3.5k RPM. So i accepted the challenge.

Symptoms:
The engine runs perfectly below 3k RPM, once it goes above this the engine starts to make a knocking sound and hold back. When i am driving the bike bogs down until +/- 2k RPM and then picks up in rpm again.

What have i done so far?
  • Cleaned the carbs
  • Changed the spark plugs
  • Checked the valves; they were perfectly in spec
  • Changed oil/ filters etc
  • Checked the static timing (didnt check the dynamic timing because i dont have a stroboscope)
  • Checked the timing advancer; Seems to work good, oiled up the axles for good luck
  • Checked the wire that leads to the spark plugs; 1.5k Ohm each

So what is up next? I am wondering if it is the Ignition coil but i find it weird that it runs and starts perfectly but then suddenly not at 3/4k rpm ??

If somebody had this issue before and fixed it please let me know
 

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It seems that the KZ400 and 440 did not age very well but with determination, time and money they can be made to run right but if its a belt drive you may have bit off more than you want to chew.

At around 4k the advancer should be fully engaged so one thing I would do is to borrow or buy a strobe timing light.
Used ones are not all that expensive.

If it has CV carbs did you check the diaphragms for smooth rise and fall with a bit of air pressure, or by hand?
 

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kz440 LTD D1 1983
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Discussion Starter · #3 ·
I borrowed a multimeter to measure some electrical stuff since I noticed the front light bulb acting weird when up in the high RPM.

I measured the ignition coil and the main coil has a short; this should be between 1,8/2,8 ohm. I also believe I heard some electrical ticking/shorting/popping noises in the front of the bike, could this be the culprit??

Then I measured the IC ignitor but couldn't make any sense out of it because the multimeter was **** hahah, at least no shorts.

At school I have some professional multimeters so I will check there today for values.
 

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Aged poorly? You're being nice. Have you adjusted the valves. Do you have the Factory "Service Manual"? Did you check the carbs? The knocking sound, depending on it's frequency, can be very tight, valves beating the cam shafts to death. I had a girlfriend who had one of these, it was a nice little bike, the one she had was pristine. The knocking would have me checking the valves first. :)
 

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kz440 LTD D1 1983
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Discussion Starter · #6 ·
But if it were the counter balancers, wouldn't there be excessive fibration no matter the rpm? If the rpm picks up it becomes worse but still i am hearing nothing from below 3500 rpm. And is there a ''easy'' way to check if these are damaged?
 

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Not necessarily and there is no easy way to check as it requires splitting of the cases to get access.

I would eliminate timing as a cause, by checking idle and high rpm timing with a proper timing light. Even if you have to pay an hour's labour to a shop to have it done or just buy one with the money you saved by not paying the shop an hour's labour. I see them on Ebay for as little as $38.

You did not answer my question about diaphragms.
 

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Yes, it is the rubber membrane. Try gently blowing compressed air into the top port of the carb entrance. The slide should smoothly rise. How high it rises depends on the flow rate of compressed air. As you increase the flow it should rise to the top and then when the compressed air stops, it should smoothly descend in about one second or so.
 

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The knmocking sound could be the ignition timing advancing for some reason. A timing light would show this with the bike on the center stand. If you happen to have a torn membrane on the carburetors, you can temporarily fix them but cutting up a heavy duty condom and use some "Flex-Seal", to attach-h to the tear, using as little of both as necessary, this patch would go on the top, away from the gasoline side. This would patch up the slide good enough to see if that is the problem. You might have to re-sync the carb. I've done this for people, and they never replaced the membrane for the CV carb. I'd advise replacing it, if you can find it. Some are very hard to find for obscure carburetors.

In rereading your post, you say you have a shorted coil, you did replace that right? You wouldn't go further without taking care of that issue first/ Just curious as you haven't addressed the resolution of that problem. Also, coils are replaced in pairs. They went on as a pair, the other one will be failing soon. Don't use the new I.C. Ignotor till you replace the coils, you could ruin it. ;)
 

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Discussion Starter · #13 ·
Thanks for the answer!

I double checked the coil with a good multimeter from work and it said 3 ohms on the main coil and 12,5k ohms on the secondary coil, so it's basically perfect. I also cleaned up the contacts since these where a little corroded.

The IC ignitor will probably not arrive this week so I'll check the carbs again in the meantime.

A friend of mine has the timing light so I will check that next weekend
 

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These little 400 are nice bikes. If you get this one going, they make a nice cafe racer. I only asked about the coil because of this statement:

"I measured the ignition coil and the main coil has a short; this should be between 1,8/2,8 ohm." I was hoping to clearify that, which you did. I hope you get this running. :)
 

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Discussion Starter · #15 ·
I checked the carbs and did in fact find two small cracks in one diaphragm, temporarily fixed this with some bicycle tire fixing glue and a small plastic bag. Worked pretty well lol.

I put on the new IC ignitor, went for a ride, aaaanndd.....

Nothing different 😒

I stopped to check the noise better and revved the engine to 4k rpm and it went up to 4,5/5k and then just died instantly.
Tried to start it again but the engine was very hard to crank via electric start, felt like it almost seized up the cylinders due to the heat.
Waited a minute and when it was cooled down I started it with some choke and it ran again... very strange

I also noticed a new sound when I was riding and it sounded like something was rattling inside the block.

I guess my only option is to open the block fully and to check everything...
 

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You never responded to this suggestion:

"Try gently blowing compressed air into the top port of the carb entrance. The slide should smoothly rise. How high it rises depends on the flow rate of compressed air. As you increase the flow it should rise to the top and then when the compressed air stops, it should smoothly descend in about one second or so."

Did you conduct this test?

But with the new sounds you are hearing, you might have some serious engine problems.
 

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Discussion Starter · #17 ·
So i made a video of the stationary rpm:

And a video of the sound i am getting, it is best heard in this video when going down in RPM from 4/3k. This is not always the case:

The videos are when the engine was semi-warmed up but the knocking/ pinging doesnt go away when fully warmed up.

Will test the dynamic timing right now with a timing light. And also check the air check into the top port (if its possible wiithout compressed air 🤔)
 

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It could have jumped on a tooth on the overhead cam chain. This is not a bike really worth putting any money into. If you could find a whole running engine cheap, really cheap, off of EBAY, then maybe, but I wouldn't pay $400 bucks for one of these running in good condition. Just trying to be honest. The diaphragms must be replaced, the bike will nickel and dime you to death. The engine sounds horrible. There are so many things that could be causing the problems and sounds you have going on. Taking it apart isn't even worth the time.

There's one on EBAY now for $200 bucks.

Link = KAWASAKI KZ440 ENGINE RUNNING | eBay
 
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