Poor Low RPM Performance

1982 KZ550 LTD

Hello all, I have a puzzling problem.

I have a heavy and constant miss from one of the right two cylinders. I have not figured out which one yet (grounding a spark plug wire causes another miss). It can be heard very loud from the right side exhaust pipe. Because of this miss, the bike stumbles upon acceleration and light cruise until about 3000 rpm. I have to slip the clutch longer than I'd like for a smooth takeoff.

In the last 2000 miles, I have performed the following engine related repairs. -

Set valve clearances on the loose end of spec. None were dangerously tight before adjustment. Verified cam timing per Lou's website. Installed cam chain tensioner after the valve cover was installed, per Lou's warning.
Used aluminum scraps and JB Weld to seal the choke flaps as all four were missing. Added Lou's fast-idle modification to compensate.
Dissembled and cleaned carbs twice. Reassembled with K&l carb kits. Carbs were left on the rack, but every passageway was blown out with carb cleaner and compressed air. Carbs were actually pretty clean. No broken vent tubes in the carb bowls.
Float levels checked with clear tube. Float level was raised slightly.
Synced the carbs 4 times. (every sync the carbs are way off). Last sync was last week.
Replaced head-to-carb boots and carb-to-airbox boots.
Removed clean air system. Plugged valve cover and airbox ports.
Dyna pickups. Dyna green coils. Coil primary wire screws are covered in silicone sealant.
Ignition advancer lubricated with synthetic Moly grease. Free movement of ignition advancer verified last week.
New Spark Plug wires. New NGK spark plugs (both replaced less than one month ago.) A very small amount of lock-tite was used on the spark plug terminal nuts as they kept working loose. Plugs gapped at .030.
Replaced leaking exhaust header gaskets. They still leak but it is much less than before, and I do not wish to break an exhaust stud. Attempted to seal the rest of the exhaust system. Removed and plugged leaking exhaust crossover pipe.
Sintered bronze fuel filter. Fuel flow is plenty.
Every exhaust pipe is hot. Water steams off each pipe.
Sprayed starting fluid and WD40 around the carbs and carb boots. No change in the miss or idle speed.
New battery and charging system. I still do not have the charging performance that others have. I have been reducing loads to compensate.

Two other problems that I have that I believe are related -
Bike loses two cylinders in the rain. Under heavy throttle, the bike spark knocks. Does not knock all the time.

I use premium fuel but Michigan gas has ethanol in it.

Since this problem has arisen, I set the carb air screws to out 1 full turn from seated. This eliminates the stumble and makes the bike rideable again. The miss is still there at idle but not as often/as constant. It goes away as soon as throttle is applied. Besides the miss, the bike runs fantastic and feels stronger than a 33 year old 550 should.

This air screw adjustment tells me I am running lean. I am not sure how as I have a stock exhaust and an airbox, and would not explain my problems in the rain.

If the miss goes away with throttle I'm inclined to think it's a carburetion issue. Why are you having to sync so often?

Topper wrote: If the miss goes away with throttle I'm inclined to think it's a carburetion issue. Why are you having to sync so often?

Me as well.

The first sync was after the carbs were reassembled.

The second sync was shortly after because I felt I could do a better job.

The third sync was 2 years later, because it had been two years since last done and I had the gas tank off.

The fourth sync was done after this miss issue (I figured maybe I hadn't tightened a locknut)

If after 4 carb synchs you have that much variation then it sounds like something is moving that shouldn't and you've made sure of the locknuts.....check if all the O-rings are good and all those little springs behind the idle jets are OK. I would also check all the connections to the coils and ignition system are OK as well as the space between the coils and the frame (no shorting). As you are losing 2 cylinders in the rain (and have poor charging performance) .....that seems to point to intermittent electrical issues causing the missing. Which 2 cylinders are cutting out? If 1&4 or 2&3 then it might be one of the coils at fault. My 0.02

bluezbike wrote: If after 4 carb synchs you have that much variation then it sounds like something is moving that shouldn't and you've made sure of the locknuts.....check if all the O-rings are good and all those little springs behind the idle jets are OK. I would also check all the connections to the coils and ignition system are OK as well as the space between the coils and the frame (no shorting). As you are losing 2 cylinders in the rain (and have poor charging performance) .....that seems to point to intermittent electrical issues causing the missing. Which 2 cylinders are cutting out? If 1&4 or 2&3 then it might be one of the coils at fault. My 0.02

www.kzrider.com/forum/4-electrical/59777...r-rr?start=40#673328

This is a history of my charging problems. Long story short, the battery will not stay charged with every light on. I have added a headlight switch and am in the process of using LED bulbs. Already switched over the taillights. With my headlight off I have not had a dead battery since.

I remember tightening the jets in, but who knows, I guess they could be loose.

All my crimps were covered in heat shrink. Perhaps I missed one (maybe the six pack of Labatt's I drank when installing the Dyna has something to do with this.)

The_Proletariat wrote: This is a history of my charging problems. Long story short, the battery will not stay charged with every light on. ......... Perhaps I missed one (maybe the six pack of Labatt's I drank when installing the Dyna has something to do with this.)

You may have said the magic word - Dyna. My understanding is that at least some models of the Dyna ignition systems draw more current that the stock ignition systems. If that is the case with yours, your bike's charging system may not be putting out enough ooomph to run the dyna and run your lights (maybe at low rpm). I suggest you check your charging system with the lights on to see if there is sufficient charging at low rpm to run the ignition system and lights and still charge the battery. Ed

650ed wrote:

The_Proletariat wrote: This is a history of my charging problems. Long story short, the battery will not stay charged with every light on. ......... Perhaps I missed one (maybe the six pack of Labatt's I drank when installing the Dyna has something to do with this.)

You may have said the magic word - Dyna. My understanding is that at least some models of the Dyna ignition systems draw more current that the stock ignition systems. If that is the case with yours, your bike's charging system may not be putting out enough ooomph to run the dyna and run your lights (maybe at low rpm).

Ed,

From reading Dyna related threads here, my understanding is the one phase charging systems have trouble with the Dyna, but the 3 phase are fine. I have a 3 phase.

I suggest you check your charging system with the lights on to see if there is sufficient charging at low rpm to run the ignition system and lights and still charge the battery. Ed

I have. This bike will not charge the battery at low rpm with the lights on.

At this point the only thing that has not been replaced is the rotor. Perhaps the magnets are weak after 33 years. I am not paying what Kawasaki wants for a new one to find out.

When younger and broke... I milked a well used 12v battery and poor charging system in my late 60's Triumph Bonneville for over two seasons by using a small 12v @ 400ma $8.00 power supply from Radio Shack.
Almost every or every other time I parked for the night I just clipped it onto my + battery terminal and ground.
The headlight was manual on-off of course so there was not much load except at night... and it did not have electric starter! LOL.

I bet a similar $5-$10 wall wart would do the same until you sort it out.

I believe I may have resolved this issue. I found a rotted vacuum line.

I cannot find vacuum lines or caps that do not crack within two weeks.

The_Proletariat wrote: I believe I may have resolved this issue. I found a rotted vacuum line.

I cannot find vacuum lines or caps that do not crack within two weeks.

Perhaps the petcock is allowing some gasoline into the vacuum line (causing rapid deterioration of a hose not designed for exposure to fuel). For example, common automotive windshield wiper hose may be poorly suited for use as a fuel line, but perform okay as a vacuum line where there's no contact with fuel.

Here's a link to vacuum plugs offered by Z1E:
Z1E vac plugs

Good Fortune!

Patton wrote:

The_Proletariat wrote: I believe I may have resolved this issue. I found a rotted vacuum line.

I cannot find vacuum lines or caps that do not crack within two weeks.

Perhaps the petcock is allowing some gasoline into the vacuum line (causing rapid deterioration of a hose not designed for exposure to fuel). For example, common automotive windshield wiper hose may be poorly suited for use as a fuel line, but perform okay as a vacuum line where there's no contact with fuel.

Here's a link to vacuum plugs offered by Z1E:
Z1E vac plugs

Good Fortune!

That's a steep price for 5 vacuum plugs but I guess if they last more than 2 weeks I'll break even.