cvk34 vulcan 500 carb problem

Do both carbs have separate gas lines, with one being kinked?

Ian Singer

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Nope. One gas line to both carbs. Also, as far as I understand there is
no fuel filter on this bike. Regardless if there is or isn't, gas runs
freely from the petcock in the "PRI" position, so it isnt a fuel
obstruction.

 

On November 5th, you said,

" I havent touched the floats, but the fluid
level is about 5mm short of the base. While this isn't optimum I don't
imagine it would be bogging the bike down."

I looked at the CARBURETOR PARTS diagram for the 1997 EN500 on
www.partsfish.com and it shows a solid drain plug on the float bowls.

The typical way of checking fuel level with the float bowl installed is
to attach a clear plastic fuel line to a nipple that comes out of the
side or bottom of the float bowl.

Then the fuel line is held up alongside the float bowl to see where the
fuel level is in relation to the gasket surface between the mixing body
and the float bowl.

Typically, it woild be about 0.5mm to 1.5 with the carburetor in the
horizontal position.

I'm wondering how you determined that the "fluid level is about 5mm
short of the base".

If the fuel level is really that low, the carburetor would have a very
hard time sucking gasoline out of the float bowl.

It's probably impossible to install the slides backwards in the
carburetors, as they are probably built asymmetrically. But, if it
*was* possible to put the slides in so the beveled side faced to the
rear, the off-idle mixture would be too lean.

It used to be possible to install carburetor slides backwards, and I
actually did that on my first Honda. The slide wouldn't close all the
way, it hung up on the idle sped screw which stuck out of the side of
the carb.

It has been said the the mechanics at the CZ factory purposely
installed the slides backwards in motocross bikes going to the hated
USSR...

 

schreef:

You said that stupid ideas are welcome.
So I give you one.

Let me assume that you yourself are not stupid.
The carbs are clean, all parts are in the correct
place and in the correct position.

it looks as a 'common' problem to me.

One 'common' thing is fuel. But you have fuel
with the pet cock in PRI (the pet cock will
have a filter), thus there is neither a filter
problem nor kinked fuel line, nor clogged vent
opening in the tank cap.

Next 'common' thing is the IC igniter.

I remember that you wrote somewhere in this
lead that you went home on one cylinder
because a 'boot' was not okay.
Now I don't know what a 'boot' is, but I suppose
that one spark plug was not connected to the
HT coil.

One thing that you (and others, and I) never should do
is to disconnect a spark plug on a running
engine. It blows out the IC igniter. (If you want
to know why, let me know)
So check that expen$ive IC igniter.

Below is my contemplation about what
can be the problem.

The IC igniter is composed of a chip (8mm dia)
that has two inputs (the pick up coils) and
two outputs. Each output goes to a
transistor, called a driver, and each
driver outputs to a Darlington transistor.
The Darlingtons act as the old fashioned
ignition points, and they each output to their
respective ignition coil.

The chip is the 'common' thing in all this.

Basically the chip has only one function.
It delays the trigger signal (from the
pick up coils). Delay depends on the time
between successive fly-by's of the pick up
coils). If time between fly-by's is long
(at low revs), the delay is long. If time
between fly-by's is short, the delay is short
(high revs).
Contrary to the old fashioned mechanical device
that advanced sparking at high revs, this chip
delays sparks at low revs. The effect is
the same. You should not wonder why.

You may argue that the IC igniter is a digital
device, and that digital devices either work
or don't work (as my computer), but a
delay line (as it is called) can be made
very cheap as a resistor and a condenser, which is
an analogue part. And analogue devices either work
OR WORK A BIT, or don't work at all.
'Work a bit' is what I am aiming at.

If you open the throttle, timing (delay)
must be changed because the engine revs up.
If the delay line is defective, sparks come too late
and the engine dies.

FWIW

Rob

 

I've kind of been worried about that myself.

I've pullled both the plugs out of the engine and ground them to the
block, and the plugs DO spark. The quality of that spark is beyond me
though.

Is there any way other than a garage that could tell me if it is an
electronic issue? I have no way of actually getting the bike to the
Kawasaki Dealer otherwise I would.

While I do not recall pullling the wire off the plug while it was
running, it may have happened. I did run it on one cylinder for about
4km before I got it home, though.

I call the "boot" the covering or cap that goes over the top of the
spark plug. It is an "L" shape and contains the brass connector that
attaches to the plug, a resistor and a spring.

Speaking of which, which way does it go? Spring, resistor, connector?
Thats how both of mine are hooked up.

And would a bad IC ignitor be the cause of the engine dying at throttle
input?

 

If its sparking, it's OK. I mean, modern electronic ignition systems
either work or they don't.

It's not like you get the timing slipping because the points gap has
changed, or anything.

And a big igniter would not cause it to die as you open the throttle,
no. It's got to be fuel-related.

 

Okay, thats a life saver.

I think I may have to offer a case of beer to whoever figures this bad
boy out.

Oh, and I checked the float level by using a vinyl tube against the
carb. To double check I even put the carb in a glass and slowly dripped
gas into the intake. Maybe I bent the floats. Im going to attempt that
today at some point (Its beautiful out today, the bikers driving by are
making me sad) and I will report back later tonight.

 

Yeh, sorry this has done you no good at all.

Right or wrong ( I don't usually volunteer but have committed myself ) here
is my 2 peneth.



The bike starts you say. Does it start with out the choke? Yes would
indicate rich ( depending on air temp).



Clean the plugs, start the bike then, try to give it throttle. Stop the
bike and look at the plugs.

Are they wet with fuel? Yes indicates 'bogging' white and dry move on.



Can you rise the slide? The slide should rise and return with a light 'clunk'



While the bike is idling, can you physical rise the slide? (with a small
driver or wire)

Do the revs rise? ( keep a finger on the cut out in case they run away) or
does the engines stall?



While you are doing the above, check tightness of battery terminal, terminal
to coil, etc. look at the carbs. Can you see the mechanism moving as you
twist the grip?



Give full choke, do the revs rise a little or does it seem to rev with
throttle?



Sorry, all questions, but relevant.

 

Contrary to popular belief, it does NOT take God's Own Lightning ® to
increase engine RPM from idle to part throttle.

Motorcycle engines have been built for decades with inexpensive low
voltage ignition systems so that the total number of parts in the
system would be reduced to a minimum, while allowing the engine to rev
up to 10000 RPM and beyond.

I have expounded upon this design compromise extensively, so I won't
get into it again.

Basically, you don't *need* any more voltage at the spark plug than it
takes to jump the
spark plug gap at whatever pressure exists in the cylinder at the
moment.

If you told me that your engine was crapping out and misfiring at high
RPM, I would say the ignition system is one of the indicated suspects.
But you're saying that the engine won't accept any throttle at all
without dying and that points at spark plugs that are on the verge of
death or very lean idle mixture due to low fuel level or plugged up
idle mixture circuits.

If you loosen the spark plug cap so you can pull it off while the
engine is running, and let the spark jump from the plug cap to the
spark plug, a spark that jumps 1/4 of an inch
indicates that you have about 9000 to 12000 volts and that's plenty to
extract all the performance that vulkin' motorbike can produce.

You might need to put a long screw or something in the cap so it
extends out to the spark plug, and do hold the cap with something
insulated so you don't become part of the circuit.

Back in the Good Old Days ®, we used to buy $6.66 K-Mart coils that
were designed to
put out 35000 volts. We installed them on our motorbikes, expecting to
achieve a Huge Performance Increase, but all we got was spark plugs
that stayed clean longer, and ignition points that burned out quicker.

It doesn't matter how much maximum voltage you have, as long as the
engine starts and runs up to maximum RPM without misfiring.

Articles by the mortal Gordon Jennings indicated that the basic problem
with low voltage motorcycle ignition systems wasn't the voltage, it was
the *voltage rise time* across the spark plug gap, and whether or not
the spark encountered burnable hydrocarbon/air mixture in the plug gap.

The voltage rise time is more critical with 2-stroke engines, where low
voltage can leak away faster than it builds up, and the spark plug wet
fouls.

But you don't have a 2-stroke, and your problem seems to be a lean idle
mixture due to low float bowl fuel level.

 

The Older Gentleman schreef:

I stated: IC igniters are NOT digital circuits. Parts of it are
analogue devices, and THUS may work a bit but not fully to
specs.

This is what happened to the IC igniter on my former LTD440. It
probably it is the same thing as on the vulcan 500. The LTD
started normally, sparks looked okay, but if I revved
it up, only one cilinder worked.

I repaired the IC igniter, and everything was fine after that.
So I had an igniter that worked at low revs, but not
at higher revs.

In my igniter one of the darlingtons was defect, but
still worked! (That darlington looks like a transistor with
three 'legs', and acts as the ignition point in the good_old
mechanical system).
The darlington did not amplify enough, but it still did amplify, and
I got a spark.
See http://en.wikipedia.org/wiki/Darlington_transistor
for the basic configuration of a darlington, but the darlington
in my igniter had a lot more components in it's body.

After I replaced the darlington (2 US$ but a lot of work) I tried to
figure out what *might* have happened.

Igniter systems work by first sending a current
through the primary winding of the ignition coil.
That crates a magnetic field in the coil.
The moment that current is stopped, the coil
creates HT in the secondary winding, because
the magnetic field suddenly disappears. This
also is true for mechanical ignition points. Opening
ignition points makes the spark. Closing the points
does not create the spark at the plug.
When the darlington does not amplify enough
the current through the primary coil is not very
high. And thus the coil is not fully magnetized
and thus the HT generated is lower than
wanted when the current is interrupted.

Current through the primary winding needs time to
build up to the maximum (usually about 4 Amps)
because the magnetic field has to be created,
and that costs energy to do.
At high revs, time between wanted sparks gets
shorter, and 4 Amps is not reached between
succesive sparks. This even gets worse if the
darlington (which acts as ignition point) cannot
output enough current himself.

So I had an IC igniter that worked at low revs,
but not at higher revs.

You are probably right. All I wanted to say is that
matt_trenholm is so focused on the carbs that
he could overlook another area.

Matt himself said he'd welcome stupid ideas.

Rob.

 

Thanks for that. I stand corrected. That said, a modern Vulcan may have
a digital ignition system anyway, but I'm fascinated to see that an
analogue system can work up to a point.

What's particularly amusing is that the old Z400/440 series (as I'm
sure you know) used a 360 degree crank, and the older points-igntion
bikes had just one contact breaker set, working on the wasted spark
principle. So it wasn't easy to have an ignition fault that only
affected one cylinder.

And they went to electronic, and had a problem. I like that. Mind you,
I've never ever encountered an electronic system that worked partially,
but it's as well to knwo it can happen.

Could just be the Bad Bike Pixies.

 

schreef:

Matt,
Somewhere in this lead I remember that you
asked for the sequence of a spring and a resistor
in the plug cap.
I cannot find where you asked this, even am
not sure if it was you who asked. But....

For electrical current it does not matter if it has
to pass a spring first and then a resistor
or the other way around.
So it does not matter (but of preferably there should
be contact between these parts).

The resistor is only there to make radio listeners
and TV viewers happy. Your sparks won't
interfere because of this resistor. Before they
mounted resistors in caps we all listened to AM
radio (CB) instead of FM radio, and you could hear
a moped from far away on the radio. And Fiat 1100
cars too.

You can even omit the resistor. It'll make your
sparks better (if you replace the resistor with a piece
of iron, or mount a cap without a resistor) but you'll
interfere and maybe that is not allowed by law where
you live. In Holland it is not, but I've never been
stopped by a police officer that said: "Let me see
your caps son".

BTW. Spark plugs themself can have built in resistors.
Having those plus a resistor in the cap is overdone,
but does not matter as long as the ignition system
is okay.

I remember that NGK uses the R in the spark plugs
type for plugs with a built in resistor. Like
D9EA and DR9EA. But all this is not really important. I
simply mount what the manual describes and I even
do not know what is inside the caps.

Rob.

 

I removed the resistors from the caps of my water buffalo. I
substituted short pieces of brass for the resistors, as brass doesn't
corrode.

The theory was that the spark plug needed all the *current* it could
get, current X voltage
increasing the power to the spark.

I couldn't see any difference in seat of the pants performance.

 

schreef:

Never had a radio that played but sounded distorted?

IC igniters (the vulcan's too) are digital devices in the sense
that they have two states.
-- Current to the coil, and
-- No current to the coil.
So you are correct. And usually a transistor either
works or does not work.

But transistors themself are analogue. They amplify an
input current. Well, they do not really amplify. Think
of them as a variable resistor of which the resistance is
controlled by an input current. The ratio of output current
and input current is called gain.
But there is a limit to what they can output. Which is
the limit to what current can flow though them before they
burn up.
In digital equipment, transistors are used that output
to their max asap. Just a low current on the input, and
whoops, output is max. You might say 'resistance is zero',
and the output current must be kept below the burn_up
current by something else (which in our case is the
resistance of the primary winding of the ignition coil).

In my LTD, primary coil was around 3 ohms, battery
around 12 volts, thus the current was restricted to
12/3=4 amps.
The darlington is a 'transistor' that has a huge gain (well
over 1000).
The darlington in my igniter was a complex thing, with
a series of transistors, resistors and condensors.
If one of these got defect, then it can be that the
gain (say 1000) dropped to 500.
Suppose the input is 6 milliamp (comes via the
chip from a small driver transistor) and gain was
originally 1000, then max current could be
6milliamp*1000=6 amp, but limited by the coil to
4 amp (12V system, 3 ohm DC resistance of
the coil). But if gain drops to 500, then the output
can only be 6milliamp*500=3 Amps, which is
lower than the 4 amps the coil would normally get.
Like I wrote, I did not measure anything. I just
replaced it.

My VF400 is electronic plus wasted spark If Honda could
mechanically make it to withstand 20.000 revs they probably
had to leave the wasted spark too. I then would get a coil for each
cylinder, and four ignition boxes in stead of the now two.
Or....
When I was young there was some schematics around, to make
your own transistorized ignition system. The basis was that the
voltage to the primary coil was beefed from 6 Volts [vintage bike]
too 400 Volts. That could make a fat spark. But I never built that
contraption.

And of course you know that electronic ignitors usually live much
longer than points, plus that the spark timing can be controlled
finer electronically than with a mechanical governor. Finer control
makes that an engine can be placed in a chopper and in
a racer_look_alike too. All the manufacturer has to do is change the
timing properties. Oh, allright, a racer could do with some
other changes too.

And a final remark (I am a mechanical engineer) ever figured
out why no manufacturer ever came up with electronic valve
lifters? They all seem to cling on to cams.

They do exist you know. If I ever see one I'll run it over.

Rob.

 

B-12 schreef:

Not completely true. The spark has to hold a minimum amount of energy
too.

Correct, but who was talking about maximum voltage.

Which -like I wrote a couple of times- indeed is very likely to
be the problem.
But: because Matt assures us, he has assembled the carbs
to what they originally were, and that he cleaned them over and over
again, I thought that it may be an idea to look into antother
direction.
And because I once had an igniter that worked on idle, but
not at higher revs (and probably it is the same as my former LTD)
I simply said: have a look at that thing.

Rob.

 

<snip>

I'm crap with electrics anyway.

Funny, that. A few years ago I was talking with some tech guys from
Daimler-Benz. Truck engineers.

I wanted to know why you couldn't dispense with cams altogether, as you
said. You'd just need a sensor on the crank to determine its position,
and it could signal whatever operated the valves to open and close as
necessary.

And hey presto - infinitely adjustable valve timing, and no
power-sapping mechanical connection to the valves. Coupled with the
then-new common rail electronically controlled diesel engines, it would
be amazing.

They went quiet, grinned, and said: "Funny you should say that...."

The problem seems to be finding a system that will actually slam open
the valves fast enough. Hydraulics might do it. Ditto pneumatics. But
you need quite a lot of pressure (think of the force needed to push a
valve down against its spring), and it apparently gets very difficult to
reload the system in time, as it were, when you start getting to highish
revs.

Or so I was given to understand.

I agree with you - it would be a fun engine.

 

schreef:

You can test the ignitor with a multimeter, but that will
only tell you if the thing works or not. And it works, otherwise
the bike would not start at all.
My ignitor failed (one cylinder) at higher than idle, but passed
the multimeter test.

You don't need to shove the bike to anywhere.
The ignitor can probably be easily removed (mine was mounted
with a rubber band only). You need a friend with the same bike
or any other bike with that ignitor, and insert yours into his bike.
It has a single plug (with 10 prongs).
Trying it in another bike probably is what a (good) garage would
do if you handed them your ignitor for testing. Bad garages would
sell you a new one without testing, later test yours and sell it to
another sucker if it is okay.

A defective one will neither ruin the spark plugs, nor the pick up
coils of your friends bike.

Remember, I asked you what else you did to the bike besides
working on the carburettors. You replied, you drove home on
one cylinder, did something to the boot (plug cap), nothing
more. So I thought: it is a 'common' problem, maybe MAYBE
the ignitor.

Rob.

 

BMW was experimenting with electro-magnetic valve operation some years
back as well. IIRC, they essentially used the valve-stem as the core in
a solenoid and there you go. Whatever other problems the system may have
had, it was:
a) phenomenally expensive
b) required a truly massive electrical system.
Either of the above would kill it as a production system. Furthermore,
there's the question of how much electrical power it takes to run the
valve-gear. Because of the inefficiency of generating electrical power
on a motorcycle, you'll end up using _more_ engine power to do the work
with EM equipment than mechanical equipment unless the electrical
components are very low-power indeed.

--
Later,
John



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

 

The Older Gentleman schreef:

I did not mention that I am (was) a mechanical engineer for nothing.
Think of the possibility that the electronic valve open slammer
and it's counterpart, the electronic valve closer would
hickup once. Oops, forgot to close a valve this time. Will do
it the next stroke.

For some functions I prefer the mechanical solution. If I was
to desing an engine, I'd make it a double cam for each valve
(one for opening and one for closing) and a gear train iso the
cam chain. Full proof. But rather expensive.

Rob.

 

B-12 schreef:

It does (gets green). But the idea is granted. Iron would be dumb.
A bar of gold would be the best. But hey, aluminium would be good too.

They passed that law for resistor mounted caps the year I
was driving my moped as a young boy. These new caps
had a shiny metal housing, the standard ones were black
plastic. So you could tell from a glance wether a moped had
the mandatory cap or not.
So me and all my moped driving friends bought a new cap.
Almost all my moped riding friends removed the resistor. I did
not, because my moped did not run any slower than before.

The spark must have lost a bit power. But like you say that
does not make any difference.

And I doubt that half a century later any policeman (maybe
exept some that ride a bike) knows that a cap with resistor
is mandatory by law.

Rob.