KZ700 power delivery is intermittant

Hey, finally got my KZ700 running reasonably well. Put new float needles
in and new airbox piping along with a new K&N air filter. It sometimes
has very good power, but its irregular. It generally runs better at
higher RPMs, it easily gets breathless at low RPMs when the throttle is
opened up wide. I just throughly cleaned out the carbs with synthetic
cleaner and compressed air.

What could be causing this? Maybe a vacuum leak? Hopefully not the CV
pistons...?

 

If "irregular" means a warmed up engine sometimes runs better than
other
times at the same RPM, then look for particles of crud in your fuel.

Based on "easily gets breathless at low RPMs when the throttle is
opened up wide", I'd guess it may be running a little bit lean. What
RPMs are you talking about ? The K&N may have leaned it out
a little too.

Intake leak might be worth looking for. Could also be a problem in the
low speed jetting. On my bike, I have access to the low speed jet and
found that the O rings that seal the jet in place had gotten leaky. If
it was sealed, I wouldn't worry about it.

 

When you cleaned the carbs out, did you see carb cleaner squirting
freely out of the
idle mixture port, the transition ports, the pilot air jet and the idle
jet? Usually an aerosol can won't have enough pressure to squirt carb
cleaner freely out all the holes at the same time, you have to cover up
two of them with your fingers while you squirt through one hole and
watch the stuff squirt out the remaining hole.

Did you drill out the EPA anti-tamper plugs and remove the idle mixture
screws to clean that hole out?

"Breathless" could indicate two possibilities to my mind. One
possibility is that the engine is actually *bogging* from the throttle
being opened too rapidly and the vacuum drops off suddenly so the
engine can't suck gasoline out of the float bowl.

CV carburetors are designed to be resistant to such bogging at low
engine speeds. The only reason I can think of for the vacuum slides
suddenly flying up and allowing the engine to bog would be the unlikely
possibility that somebody has installed the wrong springs on top of the
slides. That is such an unlikely possibility that I wouldn't expect you
to spend much time exploring it.

The other reason for an engine being "breathless" is fuel starvation.
If the engine runs well at full throttle and high RPM, but doesn't run
well at large throttle openings and lower RPM, the symptoms strongly
point toward the idle mixture passages and orifices,
since flow through the idle passages and orifices stops at full
throttle, all fuel is then coming through the main jets.

Did you push the needle jets out of the carburetor bodies to clean out
the air emulsion holes? Air mixed with the gasoline in the needle jet
helps the break up the particles of gasoline and make them more easily
burnable.

The needle jet is that brass tube which the jet needle goes up and down
in. The air emulsion holes are tiny cross-drilled orifices.

The needle jet will either push upward into the part of the body
normally occupied by the slide or it will push downward toward the
float bowl.

Another possibility is intake air leaks. Besides the obvious rubber
hoses that attach the carbs to the cylinder head, there are crankcase
breather hoses and evaporative control system hoses that the carbs
could be getting excess air from.

The evaporative control system, if you have one, stores fumes from
evaporated gasoline in a charcoal canister. While the charcoal canister
normally passes a tiny amount of outside air to the engine, that was
taken into consideration when the carbs were jetted at the factory. The
carbs can't deal with a lot of excess air though.

When you start the engine, vacuum sucks the fumes into the intake
tract downstream of the throttle butterfly. Maybe you're getting excess
air that way?

You might experiment with disconnecting and plugging some of those smog
control hoses to see if that helps.

 

I know the stuff came out the idle mixture port OR the transition ports
as well as the other two.

The EPA plugs are still there, I was hoping I would be able to leave
them on.

This matches the symptoms pretty well.

I did not do this...gah. I did spray carb cleaner down the main jet though.

I'll definitely check for air leaks.

Damn, guess I might be opening it up again...

It wasn't hard installing them except for those rubber airbox hoses.
Those alone took me about an hour and caused a lot of sore fingers...

 

Do you think the K&N would make a significant difference? I bought it
because it was actually cheaper than the OEM filter, now I wish I hadn't..

 

K&N replacement filters are a good deal. I have them on two motorbikes.
You'll never have to buy another filter for that machine.

But don't *over oil* the filter. If you over oil it the restriction
will be too much
and the engine will suddenly choke down when you apply a lot of
throttle.

Experienced tuners know better than to try to adjust the carburetors
for about two days after they oil the filter. I found that out the hard
way. I over did it on oil.

I don't even use that red K&N oil, I wash the filters in kerosene
instead, and that it sticky enough.

If you've sprayed on so much filter oil that the filter is bright pink,
it's a wonder whether it can pass any air at all. Wash it out and start
over, following the instructions.

 

The package said the filter was pre-oiled and was ready for installation
so I didn't do anything to it.

So the bike could actually be running too rich OR lean?

The spark plugs look clean, not blackened.

 

Gotta say, that's one reason why I like to stick with OEM air filters
(just put $50 Honda filter into my VFR, actually). I'd certainly prefer
one for a bike that I'm trying to get back into running condition. Maybe
I'm stupid for spending the money, maybe I'm stupid for riding a
motorcycle, maybe I just need more sleep!

If you go that way, just keep the K&N in a bag until the OEM filter
needs changing, then drop it in. Or sell it (you can probably get new
price for it if you sell in the right place) and buy new when you need a
new filter.

Alternately, you could just go ahead and wash and re-oil the filter
according to the directions. THat way, your K&N is as close to optimal
as possible.

some rambling thoughts, hope they're helpful.

--
Later,
John



'indiana' is a 'nolnn' and 'hoosier' is a 'solkk'. Indiana doesn't solkk.

 

I would have stuck with the OEM filter...if I had one The bike didn't
even have a filter when I first bought it.

 

Maybe you can find some Ru-Glide in an auto parts store. It's rubber
lubricant. Or Dow Corning Compound, or Vaseline or KY Surgical Jelly
would help the airbox hoses to slide in and out of place. I've used
WD40 on air hoses, but other people have said that it makes rubber
stick to metal so it's hard to get off. Old rubber hoses can be
softened with Berryman's B-12. They swell up. Then they return to the
original size when they dry out.

 

Sounds like a problem with idle mix, possibly due to
dirt, posibly due to jetting., possibly due to an air leak.

I don't think you explained "irregular" yet.
Is it Ok sometimes at low RPMS but not at others ?

Is it better or worse after it's warmed up ?

Does it have fits of bad running and then get better ?

If it runs badly at first and gets better when warm,
probably too lean.

If it starts out OK and gets worse, perhaps too rich.

If it runs better sometimes than others for no apparant
reason, it may be something other than jets.

 

I'm hoping its an air leak, because the vacuum hoses are all old and im
using zip ties to hold on the air ducts. I do plan on fixing that, btw.

Once its warmed up, it idles pretty well although it is a little
unstable, it will vary from about 900 rpm to 1600 rpm. It doesn't seem
like its about to stall even when its idling low, however.

There was one time I rode it and it felt really good. The engine was
already warm. After just a few minutes, it returned to being finickey
(low and uneven power at lower RPMs)

When it's cold it idles very irregularly, is sometimes difficult to
start, and needs a while before its even ridable.

It's still irregular - the power is generally poor at low RPMs (up until
6000'ish) but it isn't consistant, sometimes it'll have pulses of power.
I did notice that the bike ran notably worse when I temporarily took out
my air filter (K&N).
Thanks for advice.

 

I recommend that you check all the electrical connectors in your
ignition system, looking for loose or dirty connections. Remove the
spark plug wires and stick a metal object into the plug caps one at a
time so you can see how far the spark jumps when the engine is running.
You should see a bright blue white spark about 1/4 of an inch long. If
the spark is purplish, red, orange or white, that indicates a weak
spark.

But, if you have the bright blue white spark, that indicates your
ignition system is working OK.

I recommend that you drill out your EPA plugs and follow the procedure
that I have previously outlined for determining what the original
setting is. Then you can spritz out the idle mixture port with B-12 and
reinstall the idle mixture screws to the original settings.

If you find that three of the four idle mixture screwidle mixture
screws are set the same, but one is wildly different, set that screw
the same as the other three. It's possible that the mechanic in the
factory screwed up the mixture setting.

Before you go back into your carbs, read the carburetor parts diagram
on www.partsfish.com and find out for sure what size jets are supposed
to be in the carbs.

It's possible that somebody has changed the jets. But, shade tree
mechanics that know enough to rejet the carbs also usually know to
drill out the EPA plugs.

Check your jet needle to see if its clip is in the correct groove. The
correct groove is normally the 2nd from the top on needles with five
grooves.

 

I recommend that you check all the electrical connectors in your
ignition system, looking for loose or dirty connections. Remove the
spark plug wires and stick a metal object into the plug caps one at a
time so you can see how far the spark jumps when the engine is running.
You should see a bright blue white spark about 1/4 of an inch long. If
the spark is purplish, red, orange or white, that indicates a weak
spark.

But, if you have the bright blue white spark, that indicates your
ignition system is working OK.

I recommend that you drill out your EPA plugs and follow the procedure
that I have previously outlined for determining what the original
setting is. Then you can spritz out the idle mixture port with B-12 and
reinstall the idle mixture screws to the original settings.

If you find that three of the four idle mixture screwidle mixture
screws are set the same, but one is wildly different, set that screw
the same as the other three. It's possible that the mechanic in the
factory screwed up the mixture setting.

Before you go back into your carbs, read the carburetor parts diagram
on www.partsfish.com and find out for sure what size jets are supposed
to be in the carbs.

It's possible that somebody has changed the jets. But, shade tree
mechanics that know enough to rejet the carbs also usually know to
drill out the EPA plugs.

Check your jet needle to see if its clip is in the correct groove. The
correct groove is normally the 2nd from the top on needles with five
grooves.

 

I recommend that you check all the electrical connectors in your
ignition system, looking for loose or dirty connections. Remove the
spark plug wires and stick a metal object into the plug caps one at a
time so you can see how far the spark jumps when the engine is running.
You should see a bright blue white spark about 1/4 of an inch long. If
the spark is purplish, red, orange or white, that indicates a weak
spark.

But, if you have the bright blue white spark, that indicates your
ignition system is working OK.

I recommend that you drill out your EPA plugs and follow the procedure
that I have previously outlined for determining what the original
setting is. Then you can spritz out the idle mixture port with B-12 and
reinstall the idle mixture screws to the original settings.

If you find that three of the four idle mixture screwidle mixture
screws are set the same, but one is wildly different, set that screw
the same as the other three. It's possible that the mechanic in the
factory screwed up the mixture setting.

Before you go back into your carbs, read the carburetor parts diagram
on www.partsfish.com and find out for sure what size jets are supposed
to be in the carbs.

It's possible that somebody has changed the jets. But, shade tree
mechanics that know enough to rejet the carbs also usually know to
drill out the EPA plugs.

Check your jet needle to see if its clip is in the correct groove. The
correct groove is normally the 2nd from the top on needles with five
grooves.

 

I recommend that you check all the electrical connectors in your
ignition system, looking for loose or dirty connections. Remove the
spark plug wires and stick a metal object into the plug caps one at a
time so you can see how far the spark jumps when the engine is running.
You should see a bright blue white spark about 1/4 of an inch long. If
the spark is purplish, red, orange or white, that indicates a weak
spark.

But, if you have the bright blue white spark, that indicates your
ignition system is working OK.

I recommend that you drill out your EPA plugs and follow the procedure
that I have previously outlined for determining what the original
setting is. Then you can spritz out the idle mixture port with B-12 and
reinstall the idle mixture screws to the original settings.

If you find that three of the four idle mixture screwidle mixture
screws are set the same, but one is wildly different, set that screw
the same as the other three. It's possible that the mechanic in the
factory screwed up the mixture setting.

Before you go back into your carbs, read the carburetor parts diagram
on www.partsfish.com and find out for sure what size jets are supposed
to be in the carbs.

It's possible that somebody has changed the jets. But, shade tree
mechanics that know enough to rejet the carbs also usually know to
drill out the EPA plugs.

Check your jet needle to see if its clip is in the correct groove. The
correct groove is normally the 2nd from the top on needles with five
grooves.

 

That's quite a bit of variation in idle speed.

Fix up the air leaks before you bother trying to find any
other problems. You might also check your ignition timing
and look for crud in the float bowls. If the exhaust system
isn't solid, try to get that tight first also. I wouldn't go near
the jetting until I'd done all of the above.

Sounds lean, but I''d expect a simple jetting problem to be more
consistent.

 

I understood that to be a very bad idea for electronic ignitions,
at least per my Haynes and Clymers manuals.

Might be better to ground them out instead of leavng them
ungrounded and potentially having the spark find its own path
to ground, possibly damaging electronic components.

I won't swear this is true for all bikes, but I'd be careful
about trying it.

 

Can I do this with a regular hand drill and bit? The only other thing I
have is a dremel.

The one time I tried checking the clip positions I couldn't get the clip
back in...is there a special circlip plier or something that makes this
easier?

 

I haven't yet checked the ignition timing, but I did just clean out the
carbs (although I didn't drill out that plug and i forgot to
specifically clean the air emulsion holes as CK mentioned). The bowls
are clean though, and the exhaust seems OK.