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TOPIC: Low top end speed + very lean

Low top end speed + very lean 03 Apr 2019 19:16 #801475

  • diracdeltafunct
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So I have hit a point where I am stuck. Bike is a 1981 KZ-440 LTD belt

I have taken this carb, cleaned it, checked all its parts 1000 times now. While I am leaps and bounds ahead of where I started I am lost on what to do next.

Bike runs okish on idle. Also seems to run well all the way through 3rd gear up until I hit about 40 mph. Once I hit 40 the revs stop going past about 4.5K and I stop accelerating (or so the spedo says). I can take first and second gear up to 6-8K revs easily with power topping off around 6.5-7K.

The engine is running lean on both cylinders. It runs ok with the choke off once warm.
There is some coughing on the carb as the engine revs down. The exhaust smells like NOx and spits some whiteish smoke. If I cover up the holes on the intake air filter the engine revs up to 3-K on its own and stays there.


I have checked:

- carb boots and holders (using carb cleaner to and listening to idle).
- cleaned and soaked all the jets/bowls multiple times
- checked diaphragms for holes tears
- cleaned slide needles
- checked vacuum on each carb by pressing up slide and watching it come down (takes 2 -3 seconds to drop with finger over vent)
- replaced float needles
- replaced spark plugs
- cleaned air filter
- replaced the stock petcock with a new one that does not have the vacuum line so I capped off the vacuum port that was connected.

I have not changed/checked:

- valves ( i just opened the cover and I ran into the images below...and now am a little scared)
- I haven't ruled out bad gas.

Other things to note:
- The baffles from the right exhaust are all but gone which most surely doesn't help the lean condition.


What would you guys do next? I need to solve both the speed issue and the lean condition so I don't melt the head on this thing. :(

Thanks in advance. (I can take video or more pictures tomorrow if need be).
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Low top end speed + very lean 03 Apr 2019 20:06 #801476

  • SWest
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If that spark advance is still like that it won't run for SHT. Clean the rust off and make sure it moves freely.
Steve
Z1b1000 1975 Z1b
Opinions expressed by me do not reflect those of the the staff or members
kzrider.com/forum/11-projects/598262-kz-...-will-it-live#672882
kzrider.com/forum/2-engine/597654-poser?start=240#704229

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Low top end speed + very lean 03 Apr 2019 20:54 #801479

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SWest wrote: If that spark advance is still like that it won't run for SHT. Clean the rust off and make sure it moves freely.
Steve


I'm no expert, but I really do think Steve has a point...
:ohmy:
1982 KZ1100A-2 (sort-of)
January 2016 BOTM
The following user(s) said Thank You: SWest

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Low top end speed + very lean 03 Apr 2019 22:03 #801480

  • diracdeltafunct
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Yeah cleaning out that mess was my next task. I ran out of daylight and figured I would check on here if the speed limit/leanness issue had other potential solutions. Yay for trying to play ahead

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Low top end speed + very lean 04 Apr 2019 05:08 #801490

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Soak it good brfore trying to take it off. If it's frozen the bike won't want to go past 3500 RPM.
Steve
Z1b1000 1975 Z1b
Opinions expressed by me do not reflect those of the the staff or members
kzrider.com/forum/11-projects/598262-kz-...-will-it-live#672882
kzrider.com/forum/2-engine/597654-poser?start=240#704229

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Low top end speed + very lean 04 Apr 2019 13:41 #801526

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I didn't see checking/setting fuel levels on your list of carb work. Incorrect levels can cause rich/lean conditions.

You definitely need to sort that advancer out, I had a 750 4cyl that ran like crap for same exact reason.
1982 KZ750-M1 CSR

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Low top end speed + very lean 04 Apr 2019 17:07 #801535

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Be careful cleaning the rust off. The advance arms should each have a tiny rubber stop . They can easily come off and are so small they just look like a bit of dirt.

Patton has posted an image of an advancer for inline-fours that clearly shows the rubber bits.

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Low top end speed + very lean 04 Apr 2019 17:51 #801541

  • diracdeltafunct
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Thanks I see pattons image now. For the moment I have some liquid wrench soaking in. The screws on the front plate holding the electronic bits are so rusted Im not sure if they are coming off intact.

In the interim I scrubbed off what rust I could from the outside with a brass brush and its already looking better. I also was now able to check the valves and the clearance on the left cylinder was far too small. On the bright side the "clacking" noise at low RPM's is now gone. Downside the vacuum is so much better in that cylinder its flooding ( I had naively adjusted the float far too far on the rich side to try and compensate for the leanness and paid for it now).

I'll probably try to get the advancer off again when I have light in the morning.

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Low top end speed + very lean 04 Apr 2019 18:37 #801545

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Soak the piss out of the bolt holding the advancer. The nut just under it has two slots in it. You can squirt some in there too so it can make it's way to the threads.
Steve
Z1b1000 1975 Z1b
Opinions expressed by me do not reflect those of the the staff or members
kzrider.com/forum/11-projects/598262-kz-...-will-it-live#672882
kzrider.com/forum/2-engine/597654-poser?start=240#704229

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Low top end speed + very lean 05 Apr 2019 06:07 #801565

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I would keep applying the liquid wrench and periodically tap tap tap the bolt & pulsing coil screws with a mallet & wood block.
Running the engine might help >> heat.
Let it sit overnight, several nights. doing the same thing. penetrant, vibration, heat, time. penetrant, vibration, heat, time.

After removing the advancer, separate the rotor from the body for further cleaning & proper lubrication. If applicable, fill the groove with grease.
Then re-install the rotor & operate the advancer >> hold the body & rotate the rotor then release >> it should snap back.

ps: I would probably stuff rags behind the pulsing coil & wipe off any excess penetrant. a disposable dropper would be handy for precision application of the liquid wrench.
...

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Low top end speed + very lean 15 Apr 2019 10:24 #802185

  • diracdeltafunct
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I just got back into the bike after having to prep/travel for a week for work.

I was able to get the timing advancer off on saturday (amazing what a few wacks from a mallet can do...). As expected I cannot get the arms to pull out at all and the bushing that the cams push on does not want to spin at all....totally rusted.

I tried soaking it overnight in some pentrating oil with no luck. I then went to heat it but I couldn't heat to hot without burning off the rubber bits. Now the advancer is soaking in a bucket of CLR to see if that can eat out the rust from between the shaft and outer bushing.

Do you guys have any more advice on how to free it up?

If not I only see one on ebay from spain, but I see a few set for the KZ550 that at a glance looks exactly the same. Do you know if this could be subbed in or if you have a secret source where I might find a replacement advancer?

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Low top end speed + very lean 15 Apr 2019 19:08 #802210

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Ok I got it free with a little more aggressive torching and some more force. It runs like a dream now.

Thank all!

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