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Motorcycles » rec.motorcycles.tech » Engine breathless at higher throttle openings
| Engine breathless at higher throttle openings [message #507938] |
Thu, 10 November 2005 03:40 |
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Sorry, i'm sure this problem has been posted before...but when I open up
the throttle more than just a little bit, the engine wheezes and the
bike slows down. I can only get the bike up to about 40 mph.
The bike also makes some clatter when it's idling...maybe valve clearance?
I just bought the bike, a 1984 KZ700 with 8500 miles. The carbs are
definitely sketchy and I plan on opening them up but I wanted to have an
idea what to look for before I went in.
Thanks for advice! It's always appreciated.
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| Re: Engine breathless at higher throttle openings [message #507939 ] |
Thu, 10 November 2005 04:11 |
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Masospaghetti wrote:
> Sorry, i'm sure this problem has been posted before...but when I open up
> the throttle more than just a little bit, the engine wheezes and the
> bike slows down. I can only get the bike up to about 40 mph.
Plan on going through the fuel system and the air intake system and
cleaning it all out.
Dirty or old gasoline in the tank. Dirty petcock with fouled fuel
filter. Fuel float valve dirty, float stuck. Plugged up idle jets and
idle passages. Really dirty or oil-fouled air filter. Install new spark
plugs too.
>
> The bike also makes some clatter when it's idling...maybe valve clearance?
Maybe. The clutch basket will rattle until you pull the clutch lever
in. The starter clutch won't stop rattling. It's under the cover on the
left hand end of the engine.
Problem could also be a loose cam chain, check the tensioner and check
the valve clearances.
>
> I just bought the bike, a 1984 KZ700 with 8500 miles. The carbs are
> definitely sketchy and I plan on opening them up but I wanted to have an
> idea what to look for before I went in.
Same game as before. Look for the EPA anti-tamper plugs and see if
they've already been drilled out. If not, you'll probably have to do it
anyway to remove the idle mixture screws so you can spritz the idle
passages out.
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| Re: Engine breathless at higher throttle openings [message #507940 ] |
Thu, 10 November 2005 05:21 |
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Masospaghetti wrote:
> Sorry, i'm sure this problem has been posted before...but when I open up
> the throttle more than just a little bit, the engine wheezes and the
> bike slows down. I can only get the bike up to about 40 mph.
Sounds like the diaphragms, assuming it's CV carbs (sounds about right).
When you take the carbs apart to clean them out (another thing you need
to do), check the vacuum diaphragms for tears or holes.
> The bike also makes some clatter when it's idling...maybe valve clearance?
All Kawasaki in-line fours of that era make some clatter while idling.
The cam chain is the typical culprit, but the valves clatter too if set
to the best place for assuring good cam wear (towards the loose end of
the spec). I suspect you have nothing wrong other than typical Kawasaki
noise, I've never had a Kawasaki that didn't sound like a freakin'
diesel at idle what with all rattling chains and clattering valves.
Do check the valve clearance. Also check the cam chain guides at the
same time. If (when) the cam chain guides wear out, the chain rubs
directly against metal, making a horrible racket, but on a bike with so
few miles that's unlikely. Also check to make sure that the cam chain
tensioner is working okay. I don't recall whether Kawasakis of that era
had a ratchet tensioner or a manual one, find a service manual. If it
has a manual tensioner, adjust it. If it has a ratchet tensioner, take
out the spring (the center bolt on the thingy), pull the tensioner,
check that it works (push the spring in and watch to see that the "foot"
sticks out and won't ratchet back in), then reset it to full in and
re-install. Then push the ratchet with a skinny screwdriver or such
until you feel it push against the chain guide and make one final
"click", then re-install the spring. (Springs get old too, and may not
make that final "click"). That final "click" tends to quieten the chain
down to reasonable levels, though Kawasaki engines of that era will
never be accused of being smooth -- they were crude, noisy, and
rough-idling beasts with the redeeming quality of also being simple
well-proven technology that even today is relatively easy to maintain.
> I just bought the bike, a 1984 KZ700 with 8500 miles. The carbs are
> definitely sketchy and I plan on opening them up but I wanted to have an
> idea what to look for before I went in.
>
> Thanks for advice! It's always appreciated.
You're welcome!
- Elron
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| Re: Engine breathless at higher throttle openings [message #507945 ] |
Thu, 10 November 2005 19:56 |
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Masospaghetti wrote:
> Sorry, i'm sure this problem has been posted before...but when I open up
> the throttle more than just a little bit, the engine wheezes and the
> bike slows down. I can only get the bike up to about 40 mph.
>
> The bike also makes some clatter when it's idling...maybe valve clearance?
>
> I just bought the bike, a 1984 KZ700 with 8500 miles. The carbs are
> definitely sketchy and I plan on opening them up but I wanted to have an
> idea what to look for before I went in.
>
> Thanks for advice! It's always appreciated.
Do all the exhaust pipes come to about the same temperature?
Check the compression and the plug in each cylinder.
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| Re: Engine breathless at higher throttle openings [message #507948 ] |
Thu, 10 November 2005 22:59 |
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Masospaghetti wrote:
> Sorry, i'm sure this problem has been posted before...but when I open up
> the throttle more than just a little bit, the engine wheezes and the
> bike slows down. I can only get the bike up to about 40 mph.
>
> The bike also makes some clatter when it's idling...maybe valve clearance?
>
> I just bought the bike, a 1984 KZ700 with 8500 miles. The carbs are
> definitely sketchy and I plan on opening them up but I wanted to have an
> idea what to look for before I went in.
>
> Thanks for advice! It's always appreciated.
Check for missing airfilter or airfilter housing leaks on the filtered
side(goes lean and will try to stall like you are describing).
J.
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| Re: Engine breathless at higher throttle openings [message #507949 ] |
Thu, 10 November 2005 23:58 |
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P.J. Berg wrote:
> Masospaghetti wrote:
>
>> Sorry, i'm sure this problem has been posted before...but when I open
>> up the throttle more than just a little bit, the engine wheezes and
>> the bike slows down. I can only get the bike up to about 40 mph.
>>
>> The bike also makes some clatter when it's idling...maybe valve
>> clearance?
>>
>> I just bought the bike, a 1984 KZ700 with 8500 miles. The carbs are
>> definitely sketchy and I plan on opening them up but I wanted to have
>> an idea what to look for before I went in.
>>
>> Thanks for advice! It's always appreciated.
>
>
> Check for missing airfilter or airfilter housing leaks on the filtered
> side(goes lean and will try to stall like you are describing).
>
> J.
The bike is actually running with the filter and filter pipes removed.
If this were the case, would running with the choke on make it run
slightly better?
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| Re: Engine breathless at higher throttle openings [message #507950 ] |
Fri, 11 November 2005 01:17 |
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Masospaghetti wrote:
> P.J. Berg wrote:
>
>> Masospaghetti wrote:
>>
>>> Sorry, i'm sure this problem has been posted before...but when I open
>>> up the throttle more than just a little bit, the engine wheezes and
>>> the bike slows down. I can only get the bike up to about 40 mph.
>>>
>>> The bike also makes some clatter when it's idling...maybe valve
>>> clearance?
>>>
>>> I just bought the bike, a 1984 KZ700 with 8500 miles. The carbs are
>>> definitely sketchy and I plan on opening them up but I wanted to have
>>> an idea what to look for before I went in.
>>>
>>> Thanks for advice! It's always appreciated.
>>
>>
>>
>> Check for missing airfilter or airfilter housing leaks on the filtered
>> side(goes lean and will try to stall like you are describing).
>>
>> J.
>
>
> The bike is actually running with the filter and filter pipes removed.
> If this were the case, would running with the choke on make it run
> slightly better?
In short, yes!
J.
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| Re: Engine breathless at higher throttle openings [message #517116 ] |
Fri, 11 November 2005 12:58 |
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Masospaghetti wrote:
> The bike is actually running with the filter and filter pipes removed.
> If this were the case, would running with the choke on make it run
> slightly better?
Probably not, your carburetors most likely don't actually have a choke
plate. Some slide valve carburetors used on the Kawasaki KZ650 in the
mid-1970's did have a real choke like a car. When you close the choke
plate, it makes the carbs suck harder and more gas gets pulled out of
the float bowls. But, with a constant vacuum carburetor, there is
usually no choke plate. There is a bypass passage around the butterfly.
And that passage is a lot smaller than the open area in the carburetor
throat when you open the throttle butterflies. So no extra fuel gets
sucked into the engine when you use the newer type of choke, which is
called a "starter".
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| Re: Engine breathless at higher throttle openings [message #517118 ] |
Fri, 11 November 2005 17:56 |
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Pale Fire wrote:
> Masospaghetti wrote:
>
>
>>The bike is actually running with the filter and filter pipes removed.
>>If this were the case, would running with the choke on make it run
>>slightly better?
>
>
> Probably not, your carburetors most likely don't actually have a choke
> plate. Some slide valve carburetors used on the Kawasaki KZ650 in the
> mid-1970's did have a real choke like a car. When you close the choke
> plate, it makes the carbs suck harder and more gas gets pulled out of
> the float bowls. But, with a constant vacuum carburetor, there is
> usually no choke plate. There is a bypass passage around the butterfly.
> And that passage is a lot smaller than the open area in the carburetor
> throat when you open the throttle butterflies. So no extra fuel gets
> sucked into the engine when you use the newer type of choke, which is
> called a "starter".
>
And how do you think this starter circuit works? By letting more
gasoline into the carb/intake, fattening up the mixture. Same function,
different principle.
J.
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| Re: Engine breathless at higher throttle openings [message #517119 ] |
Fri, 11 November 2005 18:20 |
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P.J. Berg wrote:
> And how do you think this starter circuit works?
I know exactly how it works. There's a plunger (also called a
"starter") in a bypass passage that goes around the closed butterfly. A
rather large jet (about 0.6 mm orifice size) in the float bowl supplies
gasoline. The mixture drawn through the starting enrichener can be as
rich as 1 to 1.
But, as soon as you open the throttle, vacuum drops off to the point
that NOTHING gets sucked through the enrichener bypass.
This can be demonstrated by the fact that the engine will quit if the
pilot jets are plugged up. If the starting enrichener was capable of
keeping the engine running with such a rich mixture as 1 to 1, why
would it even need the tiny amount of gasoline that would come through
an idle jet that is 0.35mm to 0.45mm orifice diameter?
>By letting more
> gasoline into the carb/intake, fattening up the mixture. Same function,
> different principle.
If the enrichener worked like you think it does, it would continue to
supply enough mixture to keep the engine running with plugged idle jets
when you open the throttle.
Go ride your motorcycle and see what happens when you're operating at a
large throttle opening. You won't notice any difference in engine
operation the way you would with a plate type choke.
When you slow down and stop, the engine will run a little rough though,
with the throttle closed.
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| Re: Engine breathless at higher throttle openings [message #517120 ] |
Fri, 11 November 2005 19:54 |
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Pale Fire wrote:
> P.J. Berg wrote:
>
>
>>And how do you think this starter circuit works?
>
>
> I know exactly how it works. There's a plunger (also called a
> "starter") in a bypass passage that goes around the closed butterfly. A
> rather large jet (about 0.6 mm orifice size) in the float bowl supplies
> gasoline. The mixture drawn through the starting enrichener can be as
> rich as 1 to 1.
>
> But, as soon as you open the throttle, vacuum drops off to the point
> that NOTHING gets sucked through the enrichener bypass.
This is not correct, it would not be possible to run a bike on a cold
morning if the enrichment circuit dropped off as soon as you opened the
throttle, try and see!!
I was working today with this exact problem! 50cc four-stroke Vespa,
plunger type cold start circuit(automatic via bi-metal and heat coil).
Place it outside in the cold and you are barely able to start
it(Accelerator pump lets you), try to drive away and it does 2Mph and
sputters till it warms up.
This proves that the starter circuit does indeed fatten up the mixture
even as you open the throttle.
But hey, I [at] m not here to argue, believe what you want....
Jørn Berg. In Norway.
>
> This can be demonstrated by the fact that the engine will quit if the
> pilot jets are plugged up. If the starting enrichener was capable of
> keeping the engine running with such a rich mixture as 1 to 1, why
> would it even need the tiny amount of gasoline that would come through
> an idle jet that is 0.35mm to 0.45mm orifice diameter?
>
>
>>By letting more
>>gasoline into the carb/intake, fattening up the mixture. Same function,
>>different principle.
>
>
> If the enrichener worked like you think it does, it would continue to
> supply enough mixture to keep the engine running with plugged idle jets
> when you open the throttle.
>
> Go ride your motorcycle and see what happens when you're operating at a
> large throttle opening. You won't notice any difference in engine
> operation the way you would with a plate type choke.
>
> When you slow down and stop, the engine will run a little rough though,
> with the throttle closed.
>
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| Re: Engine breathless at higher throttle openings [message #517121 ] |
Fri, 11 November 2005 21:13 |
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P.J. Berg wrote:
> Pale Fire wrote:
> > But, as soon as you open the throttle, vacuum drops off to the point
> > that NOTHING gets sucked through the enrichener bypass.
> This is not correct, it would not be possible to run a bike on a cold
> morning if the enrichment circuit dropped off as soon as you opened the
> throttle, try and see!!
If you have to open the throttle to start the engine with the starting
enrichener valve fully open, the idle mixture screws are set too lean,
or the idle jets are plugged up. An engine with constant vacuum carb is
particularly difficult to start by twisting the throttle because the
starter won't spin the engine fast enough to crank up very much vacuum.
Some of what little vacuum it does make at cranking speeds is needed to
open the automatic petcock. That's something else that confuses
newbies. Engine won't start after the motorbike hasn't been ridden for
a few weeks, even though he has gas in the tank.
>
> I was working today with this exact problem! 50cc four-stroke Vespa,
> plunger type cold start circuit(automatic via bi-metal and heat coil).
>
> Place it outside in the cold and you are barely able to start
> it(Accelerator pump lets you), try to drive away and it does 2Mph and
> sputters till it warms up.
>
> This proves that the starter circuit does indeed fatten up the mixture
> even as you open the throttle.
But we weren't talking about a 50cc Vespa, we were talking about a
Kawasaki 700cc
I-4.
>
> But hey, I [at] m not here to argue, believe what you want....
That's what you say. The usual routine in this NG is that somebody who
doesn't know much can't get his machine running right. So he posts a
query on rec.motorcycles.tech. Then somebody answers him. Then somebody
else who likes to argue tells the first respondant that he doesn't know
what he's talking about.
Let me point out something about the starting enrichener that you may
not have noticed. The bypass is around 1/4 of an inch in diameter. It's
pretty much straight. There's no room in the bypass for much of a
venturi, so there isn't very much pressure diferential to suck fuel out
of the float bowl. The engine has to suck air through what is basically
about the size of a straw. That's why the starting enrichener quits
working when you turn the throttle grip. Not enough vacuum to suck the
gas up.
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| Re: Engine breathless at higher throttle openings [message #517206 ] |
Tue, 15 November 2005 20:14 |
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P.J. Berg wrote:
> Masospaghetti wrote:
>
>> Sorry, i'm sure this problem has been posted before...but when I open
>> up the throttle more than just a little bit, the engine wheezes and
>> the bike slows down. I can only get the bike up to about 40 mph.
>>
>> The bike also makes some clatter when it's idling...maybe valve
>> clearance?
>>
>> I just bought the bike, a 1984 KZ700 with 8500 miles. The carbs are
>> definitely sketchy and I plan on opening them up but I wanted to have
>> an idea what to look for before I went in.
>>
>> Thanks for advice! It's always appreciated.
>
>
> Check for missing airfilter or airfilter housing leaks on the filtered
> side(goes lean and will try to stall like you are describing).
>
> J.
I opened up the carbs yesterday, they looked ok. I was concerned that it
was getting *too much* fuel instead of not enough before but this
doesn't seem to be the case...
So running the bike without the air filter and filter pipes could cause
the problem I am having, to this severity? I never thought it made such
a large difference.
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| Re: Engine breathless at higher throttle openings [message #517207 ] |
Tue, 15 November 2005 20:16 |
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Masospaghetti wrote:
> P.J. Berg wrote:
>
>> Masospaghetti wrote:
>>
>>> Sorry, i'm sure this problem has been posted before...but when I open
>>> up the throttle more than just a little bit, the engine wheezes and
>>> the bike slows down. I can only get the bike up to about 40 mph.
>>>
>>> The bike also makes some clatter when it's idling...maybe valve
>>> clearance?
>>>
>>> I just bought the bike, a 1984 KZ700 with 8500 miles. The carbs are
>>> definitely sketchy and I plan on opening them up but I wanted to have
>>> an idea what to look for before I went in.
>>>
>>> Thanks for advice! It's always appreciated.
>>
>>
>>
>> Check for missing airfilter or airfilter housing leaks on the filtered
>> side(goes lean and will try to stall like you are describing).
>>
>> J.
>
>
> I opened up the carbs yesterday, they looked ok. I was concerned that it
> was getting *too much* fuel instead of not enough before but this
> doesn't seem to be the case...
> So running the bike without the air filter and filter pipes could cause
> the problem I am having, to this severity? I never thought it made such
> a large difference.
Oh, and if it makes any difference...when the engine is warm and I pull
the choke, the RPM's jump to about 5000(!)
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| Re: Engine breathless at higher throttle openings [message #517209 ] |
Tue, 15 November 2005 20:24 |
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Masospaghetti wrote:
> Masospaghetti wrote:
>
>> P.J. Berg wrote:
>>
>>> Masospaghetti wrote:
>>>
>>>> Sorry, i'm sure this problem has been posted before...but when I
>>>> open up the throttle more than just a little bit, the engine wheezes
>>>> and the bike slows down. I can only get the bike up to about 40 mph.
>>>>
>>>> The bike also makes some clatter when it's idling...maybe valve
>>>> clearance?
>>>>
>>>> I just bought the bike, a 1984 KZ700 with 8500 miles. The carbs are
>>>> definitely sketchy and I plan on opening them up but I wanted to
>>>> have an idea what to look for before I went in.
>>>>
>>>> Thanks for advice! It's always appreciated.
>>>
>>>
>>>
>>>
>>> Check for missing airfilter or airfilter housing leaks on the
>>> filtered side(goes lean and will try to stall like you are describing).
>>>
>>> J.
>>
>>
>>
>> I opened up the carbs yesterday, they looked ok. I was concerned that
>> it was getting *too much* fuel instead of not enough before but this
>> doesn't seem to be the case...
>> So running the bike without the air filter and filter pipes could
>> cause the problem I am having, to this severity? I never thought it
>> made such a large difference.
>
>
> Oh, and if it makes any difference...when the engine is warm and I pull
> the choke, the RPM's jump to about 5000(!)
One last thing - I did check compression, it's good (150 psi) and the
spark plugs are clean.
The diaphragms seemed alright from what I could tell (pushing them up
with my finger, plugging the port, and releasing them - they all came
down pretty slowly) and the two I can see while the engine is running do
respond to throttle inputs.
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| Re: Engine breathless at higher throttle openings [message #517211 ] |
Tue, 15 November 2005 21:10 |
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Masospaghetti wrote:
> Oh, and if it makes any difference...when the engine is warm and I pull
> the choke, the RPM's jump to about 5000(!)
Have the EPA anti-tamper plugs been drilled out yet? If you can see the
slotted heads of the idle mixture screws, they've already been monkied
with.
The mistake a lot of shade tree mechanics get into is that they expect
the engine idle speed to increase as they turn the idle mixture screws
counterclockwise. The engine speed increases to a point, and then
actually starts slowing down.
So the shade tree mechanic turns the master idle knob to make the
engine idle faster.
And the idle RPM runs away when the engine is hot. The idle RPM will
also be too high when the engine is on the choke when it's cold in the
morning.
If you can't see the idle mixture screws, the EPA plugs are still in
there and my diagnosis is that your idle mixture passages are all
plugged up and the engine gets fuel from the starting enrichener
("choke") when you open the throttle a lot, but the engine falters and
stalls at smaller throttle openings.
Been there, had that problem. Fixed it by cleaning the carbs with
Berryman's B-12 Chemtool Chose and Carburetor Cleaner in the aerosol
can.
You can open up the carbs and clean out the pilot jets and still have
idle mixture passages full of gum and varnish if yuo don't know how the
idle mixture passage goes four different ways.
With the anti-tamper plugs drilled out and the idle mixture screws
removed (1), you can squirt Berryman's B-12 through the hole the idle
mixture screw came out of and the
carb cleaner must squirt out four different ways.
1. It must come out the hole closest to the idle mixture screw.
2. It must come out the three holes next to the throttle butterfly.
3. It must come out the pilot jet.
4. It must come out the pilot air jet in the intake bell.
Since you don't have a lot of pressure out of an aerosol spray can, you
can hold your fingers over some of the holes while you are spraying
carb cleaner through any of the holes.
(1) Count the number of turns it takes to lightly seat the idle mixture
screws in the bottom of the hole. Write those numbers down on a piece
of paper. When you reinstall the screws, make sure you get each screw
back into the hole it came out of.
All four screws should probably be around 1/4th to 1/2 a turn open,
unless your carbs have extremely small pilot jets.
With CV carbs, turning the screw clockwise leans the mixture up.
Turning the screw counterclockwise richens the mixture up. What you are
trying to do when adjusting the screws with the engine running is to
get the engine to just start running rough as you turn the idle mixture
screw clockwise. Then you can turn the screw back counterclockwise
about 1/8th to 1/4th of a turn to get the engine to run smoothly again.
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| Re: Engine breathless at higher throttle openings [message #517217 ] |
Wed, 16 November 2005 01:18 |
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Pale Fire wrote:
> Masospaghetti wrote:
>
>
>>Oh, and if it makes any difference...when the engine is warm and I pull
>>the choke, the RPM's jump to about 5000(!)
>
>
> Have the EPA anti-tamper plugs been drilled out yet? If you can see the
> slotted heads of the idle mixture screws, they've already been monkied
> with.
The tamper plugs are intact.
>
> The mistake a lot of shade tree mechanics get into is that they expect
> the engine idle speed to increase as they turn the idle mixture screws
> counterclockwise. The engine speed increases to a point, and then
> actually starts slowing down.
>
> So the shade tree mechanic turns the master idle knob to make the
> engine idle faster.
> And the idle RPM runs away when the engine is hot. The idle RPM will
> also be too high when the engine is on the choke when it's cold in the
> morning.
>
> If you can't see the idle mixture screws, the EPA plugs are still in
> there and my diagnosis is that your idle mixture passages are all
> plugged up and the engine gets fuel from the starting enrichener
> ("choke") when you open the throttle a lot, but the engine falters and
> stalls at smaller throttle openings.
I don't fully understand this...because the bike idles fine when the
starter circuit is off at around 1000 RPM, but even when the bike is
warm it will rev wayyy up when the starter circuit is enabled. Won't a
correctly operating bike slow down in this condition, or even stall?
I thought the bike would be running way too lean, and that the richer
starter mixture was closer to optimal and this is why the bike would
speed up so much.
Again, the air filter and piping is completely disconnected, would this
alone cause the problem I am having or does it sound like there is
something else at work here?
>
> Been there, had that problem. Fixed it by cleaning the carbs with
> Berryman's B-12 Chemtool Chose and Carburetor Cleaner in the aerosol
> can.
>
> You can open up the carbs and clean out the pilot jets and still have
> idle mixture passages full of gum and varnish if yuo don't know how the
> idle mixture passage goes four different ways.
>
> With the anti-tamper plugs drilled out and the idle mixture screws
> removed (1), you can squirt Berryman's B-12 through the hole the idle
> mixture screw came out of and the
> carb cleaner must squirt out four different ways.
>
> 1. It must come out the hole closest to the idle mixture screw.
>
> 2. It must come out the three holes next to the throttle butterfly.
>
> 3. It must come out the pilot jet.
>
> 4. It must come out the pilot air jet in the intake bell.
>
> Since you don't have a lot of pressure out of an aerosol spray can, you
> can hold your fingers over some of the holes while you are spraying
> carb cleaner through any of the holes.
I did run cleaner through it, although I will admit I was not this
thorough. The carbs will surely be out again soon, and I will do this.
>
> (1) Count the number of turns it takes to lightly seat the idle mixture
> screws in the bottom of the hole. Write those numbers down on a piece
> of paper. When you reinstall the screws, make sure you get each screw
> back into the hole it came out of.
>
> All four screws should probably be around 1/4th to 1/2 a turn open,
> unless your carbs have extremely small pilot jets.
>
> With CV carbs, turning the screw clockwise leans the mixture up.
> Turning the screw counterclockwise richens the mixture up. What you are
> trying to do when adjusting the screws with the engine running is to
> get the engine to just start running rough as you turn the idle mixture
> screw clockwise. Then you can turn the screw back counterclockwise
> about 1/8th to 1/4th of a turn to get the engine to run smoothly again.
>
I had this experience with my KZ750 twin...oh god, what a nightmare.
Hopefully it was just a weak spark after all.
Thanks for the response, always appreciated.
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| Re: Engine breathless at higher throttle openings [message #517218 ] |
Wed, 16 November 2005 01:56 |
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Masospaghetti wrote:
> Pale Fire wrote:
>
>> Masospaghetti wrote:
>>
>>
>>> Oh, and if it makes any difference...when the engine is warm and I pull
>>> the choke, the RPM's jump to about 5000(!)
>>
>>
>>
>> Have the EPA anti-tamper plugs been drilled out yet? If you can see the
>> slotted heads of the idle mixture screws, they've already been monkied
>> with.
>
>
> The tamper plugs are intact.
>
>>
>> The mistake a lot of shade tree mechanics get into is that they expect
>> the engine idle speed to increase as they turn the idle mixture screws
>> counterclockwise. The engine speed increases to a point, and then
>> actually starts slowing down.
>>
>> So the shade tree mechanic turns the master idle knob to make the
>> engine idle faster.
>> And the idle RPM runs away when the engine is hot. The idle RPM will
>> also be too high when the engine is on the choke when it's cold in the
>> morning.
>>
>> If you can't see the idle mixture screws, the EPA plugs are still in
>> there and my diagnosis is that your idle mixture passages are all
>> plugged up and the engine gets fuel from the starting enrichener
>> ("choke") when you open the throttle a lot, but the engine falters and
>> stalls at smaller throttle openings.
>
>
> I don't fully understand this...because the bike idles fine when the
> starter circuit is off at around 1000 RPM, but even when the bike is
> warm it will rev wayyy up when the starter circuit is enabled. Won't a
> correctly operating bike slow down in this condition, or even stall?
>
> I thought the bike would be running way too lean, and that the richer
> starter mixture was closer to optimal and this is why the bike would
> speed up so much.
>
> Again, the air filter and piping is completely disconnected, would this
> alone cause the problem I am having or does it sound like there is
> something else at work here?
>
>>
>> Been there, had that problem. Fixed it by cleaning the carbs with
>> Berryman's B-12 Chemtool Chose and Carburetor Cleaner in the aerosol
>> can.
>>
>> You can open up the carbs and clean out the pilot jets and still have
>> idle mixture passages full of gum and varnish if yuo don't know how the
>> idle mixture passage goes four different ways.
>>
>> With the anti-tamper plugs drilled out and the idle mixture screws
>> removed (1), you can squirt Berryman's B-12 through the hole the idle
>> mixture screw came out of and the
>> carb cleaner must squirt out four different ways.
>>
>> 1. It must come out the hole closest to the idle mixture screw.
>>
>> 2. It must come out the three holes next to the throttle butterfly.
>>
>> 3. It must come out the pilot jet.
>>
>> 4. It must come out the pilot air jet in the intake bell.
>>
>> Since you don't have a lot of pressure out of an aerosol spray can, you
>> can hold your fingers over some of the holes while you are spraying
>> carb cleaner through any of the holes.
>
>
> I did run cleaner through it, although I will admit I was not this
> thorough. The carbs will surely be out again soon, and I will do this.
>
>>
>> (1) Count the number of turns it takes to lightly seat the idle mixture
>> screws in the bottom of the hole. Write those numbers down on a piece
>> of paper. When you reinstall the screws, make sure you get each screw
>> back into the hole it came out of.
>>
>> All four screws should probably be around 1/4th to 1/2 a turn open,
>> unless your carbs have extremely small pilot jets.
>>
>> With CV carbs, turning the screw clockwise leans the mixture up.
>> Turning the screw counterclockwise richens the mixture up. What you are
>> trying to do when adjusting the screws with the engine running is to
>> get the engine to just start running rough as you turn the idle mixture
>> screw clockwise. Then you can turn the screw back counterclockwise
>> about 1/8th to 1/4th of a turn to get the engine to run smoothly again.
>>
> I had this experience with my KZ750 twin...oh god, what a nightmare.
> Hopefully it was just a weak spark after all.
>
> Thanks for the response, always appreciated.
If the airfilter setup is missing and the carbs have NOT been
re-calibrated with larger mains(might also need larger idle jets), it
will stumble/hesitate like you describe.
J.
|
|
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| Re: Engine breathless at higher throttle openings [message #517219 ] |
Wed, 16 November 2005 03:54 |
|
Masospaghetti wrote:
> I don't fully understand this...because the bike idles fine when the
> starter circuit is off at around 1000 RPM, but even when the bike is
> warm it will rev wayyy up when the starter circuit is enabled. Won't a
> correctly operating bike slow down in this condition, or even stall?
I'm sorry. I forgot that Kawasaki put a fast idle mechanism on the
right hand end of the
shaft that opens the starting enrichener valves. On a car, the fast
idle mechanism will have some sort of dashpot rigged to a heat
controlled choke plate, but this mechanism is stupid, it just blocks
the throttle open a little bit while the choke is on, making Kawasaki
engines run away whether hot or cold.
TOG knows about this, I'm surprised he didn't catch it.
Go to www.partsfish.com and look at the Carburetor Assembly 1 2 drawing
and you will see"
13168 LEVER,CHOCK
16041 SHAFT-CARBURETOR,CHOC
92022 WASHER,SPRING
92033 RING-SNAP,E
92045 BALL,STEEL,1/8"
92081A SPRING,FAST IDLE SHFT
39184A BRACKET-ASSY,THROTTLE
|
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|
| Re: Engine breathless at higher throttle openings [message #517223 ] |
Wed, 16 November 2005 10:32 |
|
"P.J. Berg" <BergRace [at] gmail.com> wrote in message
news:Hsvef.960$zc1.239 [at] amstwist00...
X
>> Thanks for the response, always appreciated.
>
> If the airfilter setup is missing and the carbs have NOT been
> re-calibrated with larger mains(might also need larger idle jets), it will
> stumble/hesitate like you describe.
Put the airfilter back, it's there for a reason
The dust particles are going to cause extra wear to the engine
|
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| Re: Engine breathless at higher throttle openings [message #517224 ] |
Wed, 16 November 2005 14:14 |
|
Masospaghetti wrote:
> Pale Fire wrote:
> > Have the EPA anti-tamper plugs been drilled out yet? If you can see the
> > slotted heads of the idle mixture screws, they've already been monkied
> > with.
>
> The tamper plugs are intact.
> I don't fully understand this...because the bike idles fine when the
> starter circuit is off at around 1000 RPM, but even when the bike is
> warm it will rev wayyy up when the starter circuit is enabled. Won't a
> correctly operating bike slow down in this condition, or even stall?
> I thought the bike would be running way too lean, and that the richer
> starter mixture was closer to optimal and this is why the bike would
> speed up so much.
It's that fast idle cam or "chock" on the end of the choke rod that's
causing the really fast idle, plus the rich mixture from the starting
enrichener.
> Again, the air filter and piping is completely disconnected, would this
> alone cause the problem I am having or does it sound like there is
> something else at work here?
Hopefully, you have clean new spark plugs in the engine and all
connectors and the wiring to the ignition unit is in good condition.
When you remove the air filter and the intake hoses, the engine will
run a little richer at idle because there's no pressure drop across an
air filter and it will run too lean at full throttle, when the jet
needle has come up out of the needle jet about 7/8ths of the way.
It's very hard to tell where the needle is at on a constant vacuum
carburetor when you have the throttle butterflies fully open as
indicated by the fact the throttle twist grip won't turn any further.
Do-it-yourselfers get all confused by this main jet, needle jet, jet
needle, pilot jet business. People who JUST DON'T KNOW ANY BETTER will
say, "Oh, your main jet is dirty, you need to clean it out."
But you are very rarely ever running on the main jet if you're a
street rider. You're mostly running on the idle jets and the straight
part of the jet needle.
I'm not saying that the main jet NEVER gets dirty. I've seen carbs so
filthy the main jet and everything else was plugged up.
Amateur tuners think that the various circuits of a carburetor work
only at certain throttle openings. That's not true at all. The circuits
are all working at the same time, except for the enrichener, which you
always turn off.
Amateur tuners get the idea that the idle jet only works when the
engine is idling and that's not true. The engine is supposed to get ALL
of it's fuel through the idle jet up to about 1/8th throttle, but it
keeps sucking fuel through the idle jet until the throttle is wide
open. It gets less and less fuel through the idle jet as the throttle
is opened.
>From 1/8th throttle to 1/4th throttle, those transition ports
downstream of the throttle butterflies come into play to help the
engine accelerate from idle. A little bit of fuel starts flowing
through the main jets, but most of it is coming from the idle jets.
Then, from 1/4 throttle to about 1/2 throttle, the diameter of the
untapered part of the jet needle influences mixture the most. More fuel
is coming through the main jets. But fuel is still coming through the
idle jets.
>From 1/2 to 3/4 throttle, the tapered part of the needle is coming up
out of the needle jet and the area is increasing rapidly, but it's
still less area than the main jet's area, so that's what's controlling
the fuel, not the main jet. But the fuel has to come through the main
jet before it can pass through the needle jet. And fuel is STILL coming
through the idle jets.
Finally, when you get the throttle open 7/8ths to full throttle, the
engine is running on the main jets. But you have to remember that the
main jet is IN SERIES with the needle jet/jet needle orifice. The area
of the main jet ALWAYS has to be bigger than the difference in the area
of the needle jet minus the area of the jet needle or the engine will
starve for fuel at large throttle openings.
Amateur tuners go blindly guessing and buying a lot of expen$ive bra$$
jets at around
$5.00 each, or they ask other people that just don't KNOW how the jet
sizing numbers work. I've explained how the numbering system works
dozens of times in this NG.
But, you probably don't need to run out and buy a bunch of main jets
anyway. Just hook up the air hoses and install a new air filter, after
you've thoroughly spritzed out the carbs with B-12.
|
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| Re: Engine breathless at higher throttle openings [message #517232 ] |
Wed, 16 November 2005 23:49 |
|
Brother-Peter wrote:
> "P.J. Berg" <BergRace [at] gmail.com> wrote in message
> news:Hsvef.960$zc1.239 [at] amstwist00...
> X
>
>>>Thanks for the response, always appreciated.
>>
>>If the airfilter setup is missing and the carbs have NOT been
>>re-calibrated with larger mains(might also need larger idle jets), it will
>>stumble/hesitate like you describe.
>
>
> Put the airfilter back, it's there for a reason
> The dust particles are going to cause extra wear to the engine
>
>
The air filter is disconnnected because the bike didn't come with one
(one is on the way) and that I wanted to get the carbs in decent order
before I wrestled with the air piping.
|
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| Re: Engine breathless at higher throttle openings [message #517233 ] |
Wed, 16 November 2005 23:58 |
|
Pale Fire wrote:
> Masospaghetti wrote:
>
>>Pale Fire wrote:
>>
>>>Have the EPA anti-tamper plugs been drilled out yet? If you can see the
>>>slotted heads of the idle mixture screws, they've already been monkied
>>>with.
>>
>>The tamper plugs are intact.
>
>
>>I don't fully understand this...because the bike idles fine when the
>>starter circuit is off at around 1000 RPM, but even when the bike is
>>warm it will rev wayyy up when the starter circuit is enabled. Won't a
>>correctly operating bike slow down in this condition, or even stall?
>
>
>>I thought the bike would be running way too lean, and that the richer
>>starter mixture was closer to optimal and this is why the bike would
>>speed up so much.
>
>
> It's that fast idle cam or "chock" on the end of the choke rod that's
> causing the really fast idle, plus the rich mixture from the starting
> enrichener.
>
>
>>Again, the air filter and piping is completely disconnected, would this
>>alone cause the problem I am having or does it sound like there is
>>something else at work here?
>
>
> Hopefully, you have clean new spark plugs in the engine and all
> connectors and the wiring to the ignition unit is in good condition.
>
> When you remove the air filter and the intake hoses, the engine will
> run a little richer at idle because there's no pressure drop across an
> air filter and it will run too lean at full throttle, when the jet
> needle has come up out of the needle jet about 7/8ths of the way.
>
> It's very hard to tell where the needle is at on a constant vacuum
> carburetor when you have the throttle butterflies fully open as
> indicated by the fact the throttle twist grip won't turn any further.
>
> Do-it-yourselfers get all confused by this main jet, needle jet, jet
> needle, pilot jet business. People who JUST DON'T KNOW ANY BETTER will
> say, "Oh, your main jet is dirty, you need to clean it out."
>
> But you are very rarely ever running on the main jet if you're a
> street rider. You're mostly running on the idle jets and the straight
> part of the jet needle.
>
> I'm not saying that the main jet NEVER gets dirty. I've seen carbs so
> filthy the main jet and everything else was plugged up.
>
> Amateur tuners think that the various circuits of a carburetor work
> only at certain throttle openings. That's not true at all. The circuits
> are all working at the same time, except for the enrichener, which you
> always turn off.
>
> Amateur tuners get the idea that the idle jet only works when the
> engine is idling and that's not true. The engine is supposed to get ALL
> of it's fuel through the idle jet up to about 1/8th throttle, but it
> keeps sucking fuel through the idle jet until the throttle is wide
> open. It gets less and less fuel through the idle jet as the throttle
> is opened.
>
>>From 1/8th throttle to 1/4th throttle, those transition ports
> downstream of the throttle butterflies come into play to help the
> engine accelerate from idle. A little bit of fuel starts flowing
> through the main jets, but most of it is coming from the idle jets.
>
> Then, from 1/4 throttle to about 1/2 throttle, the diameter of the
> untapered part of the jet needle influences mixture the most. More fuel
> is coming through the main jets. But fuel is still coming through the
> idle jets.
>
>>From 1/2 to 3/4 throttle, the tapered part of the needle is coming up
> out of the needle jet and the area is increasing rapidly, but it's
> still less area than the main jet's area, so that's what's controlling
> the fuel, not the main jet. But the fuel has to come through the main
> jet before it can pass through the needle jet. And fuel is STILL coming
> through the idle jets.
>
> Finally, when you get the throttle open 7/8ths to full throttle, the
> engine is running on the main jets. But you have to remember that the
> main jet is IN SERIES with the needle jet/jet needle orifice. The area
> of the main jet ALWAYS has to be bigger than the difference in the area
> of the needle jet minus the area of the jet needle or the engine will
> starve for fuel at large throttle openings.
>
> Amateur tuners go blindly guessing and buying a lot of expen$ive bra$$
> jets at around
> $5.00 each, or they ask other people that just don't KNOW how the jet
> sizing numbers work. I've explained how the numbering system works
> dozens of times in this NG.
>
> But, you probably don't need to run out and buy a bunch of main jets
> anyway. Just hook up the air hoses and install a new air filter, after
> you've thoroughly spritzed out the carbs with B-12.
>
Does using a K&N filter make an appreciable difference compared to the
standard paper one? Will I run too lean with it also? I ordered one
because I actually got it cheaper than a stock replacement would have cost.
|
|
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| Re: Engine breathless at higher throttle openings [message #517235 ] |
Thu, 17 November 2005 00:19 |
|
Masospaghetti wrote:
> Does using a K&N filter make an appreciable difference compared to the
> standard paper one? Will I run too lean with it also? I ordered one
> because I actually got it cheaper than a stock replacement would have cost.
A K&N filter will flow more air or less air than a stock replacement
filter, depending on how recently you oiled it. Follow the instructions
and let the filter set to drip out any excess oil before you put it in
the airbox.
Amateur tuners who have over-oiled their K&N's and tried to re-jet
their carbs thinking the mixture would be too lean found that it was
too rich and the experts recommended not even trying to tune the carbs
for a few days until the oil spread out evenly.
K&N's are a very economical replacement for OEM filters because a K&N
won't wear out, you can just keep washing it out over and over again. I
use kerosene, not the special K&N washing liquid.
Then I don't oil the filter because I don't ride in a dusty area.
That's no problem with a motorbike that has chrome plated rings. I
wouldn't do it if I had a more modern bike with cast-iron rings and
electroplated cylinder walls, the soft rings would wear too fast.
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