Yamaha sat for 2 months, now 1 cylinder not firing and bad acceleration

I have a used 94 Yamaha XJ600 (Seca II/Diversion). It was running fine
when I got it, drove it up and down the street once every couple of
weeks just to get a feel for it. The battery died and I let it sit for
a couple of months. It starts but runs rough, 1 cylinder is not firing
(1 out of 4 exhaust pipes is warm, the rest are really hot when
running). The (vacuum operated) fuel petcock is leaking (should be off
when the engine is off, but it has a slow steady leak).

When I give a little throttle in neutral, it revs a little. If I give
a lot of throttle, it peaks at 4k and then dies (almost stalls). In
gear it wont pull at all, wont go past 2k, and sometimes gives a little
sucking/vacuum sounds (like a gentle pop) accompanied by a surge or
hesitation. Some kind of vacuum buildup? I'm getting spark, but
peaking into cylinder 1 (left most) reveals a lot of black grime. I
suspect fuel has been leaking into that cylinder (since the bike leans
left when resting on the kickstand for 2 months) and has gummed
up/varnished.

I've seen lots on how to clean out carbs, but how to clean up the
cylinder itself? Also, how do I check if that carb is plugged too? I
sprayed carb cleaner into the intake, didn't have any affect. The
carbs look clean from above, no dirt or varnish. How do I check if
fuel is getting to that cylinder?

I've got carb cleaner, fuel system cleaner, HEET (methyl alcohol), I
can get isopropyl alcohol and acetone. What should I use? Should I
put something in the fuel system and run it through, hope it gets to
cylinder 1? Should I spray any of the above directly into the
cylinder? Will I have to take the carb off to see if it's working or
gummed up? Any suggestions appreciated.

 

Install a new spark plug in that cylinder or swap plugs between
cylinders to see if the symptom moves to another cylinder...

Problem is probably a plugged up idle jet in the #1 carb...

The (vacuum operated) fuel petcock is leaking (should be off

Buy a petcock rebuild kit and install it (after draining the gas
tank)...

Your idle jets are plugged up. The engine really really really needs
those idle jets to be clean in order to accelerate...

You probably have plenty of vacuum to suck gas into the engine, but if
the idle jets and passages are plugged up, it can't get the fuel it
needs...

Has the oil level been mysteriously rising? Remove the oil filler cap
on the clutch clutch and put your nose down there and sniff for
gasoline fumes. Does your oil smell like gasoline? Oil that has been
diluted with gasoline doesn't lubricate well. You could even have a
crankcase explosion if there are a lot of gasoline vapors from fuel
leaking past the piston rings.

There are commercial decarbonizing products that you will find on the
chemicals shelf at your local auto parts store. On a motorcycle, you
just mix a few ounces on each tank of gas until you've used up the
whole can...

Never spray carb cleaner into the intake unless you're just trying to
unstick the vacuum slides. That might take a few drops of carb cleaner,
then you work the slides up and down with your finger and that's done..

An engine that isn't getting idle mixture to the engine will go
fartPOP! or piffle-piffle-SNAP out the exhaust...

Any good auto parts store will have Berryman's B-12 Chemtool Choke and
Carburetor Cleaner in the 15 ounce non-aerosol can. Put three ounces in
a fuel tank of gasoline and ride slowly, watching for fast traffic
coming up behind you. You want to ride along in first gear for a while,
as slose to iidle speed as possible. When the engine gets hot, ride
faster and cool it off. When the B-12 starts working, the engine idle
speed will increase...

Don't use fuel system cleaners meant for fuel injection systems. They
contain a lot of petroleum distillate (solvent like kerosene) that
won't do the jon you want. Fuel injector cleaners lubricate the pintle
of the fuel injector, and you don't have fuel injectors...

HEET is for starting cold engines and it mixes any water that is in the
fuel system with alcohol so your engine can suck it out of the carbs
and blow it out the exhaust as steam. HEET would do that part of
carburetor cleaning, but B-12 is better. You can get it at Walmart or
Pep Boys or any decent auto parts store

No, anything containing alcohol may dilute the oil film on the cylinder
walls and you could scuff the cylinder walls. If you put B-12 in the
gasoline, don't run the engine really hard, don't use high RPM or
overheat the engine. Alcohol isn't particularly good for engine
lubrication...

Will I have to take the carb off to see if it's working or

If the B-12 doesn't "get 'er done", you will have to remove the entire
bank of carbs and follow the thorough clean out procedure I have
described a bazillion times. Google for "[email protected] +idle jets"...

 

What is the condition of the battery now? Is it near death?

What do the plugs look like?

Note the subthread "Decarbonizing without engine disassembly" started in
this group near 06/15/2005 08:58 AM, wherein krusty kritter indicates
some techniques for clearing carbon out of the combustion chambers.

I found that running at high revs in a low gear, say 45mph in second,
cleared carbon out my cylinders nicely. Hmmm, but it looks like your
bike won't do that at the moment.

 

When I pulled plugs (after a lot of unsuccessful starts) they were
comletely carbon covered. Cleaned them out with a wire brush, they
look great now. I haven't run it more than 10 minutes at a time since,
so I don't know how they'll hold up.

Got a new battery, seems to be holding up. Even after a lot of
cranking, no signs of fading. Good thing.

I managed to get the carbs off, and I started disassembly per the
Chilton's manual. Trying to get the throttle valve cover off and the
darn screws are stuck (almost stripping them trying to get them out).
I'm spraying in WD-40, dont' know what to do next. I always get stuck
at this point; corroded stuck parts. Should I just keep trying
penetrating oil? Heat it up? Easy out? I hate this part.

I got Berryman B12 Chemtool and Chem-dip carb and parts cleaner. Maybe
I should've tried B12 in the gas first, see if it cleared itself off.
I suppose I can slap the carb back on and try. Should I get at the
stuck screw, or slap everything together and hope on the B12 first?

 

Wowsers! I opened up the other end of the carbs (bowl cover, where all
the fun stuff is) and look what I found:

http://img67.echo.cx/img67/2208/badcarb13jc.jpg
http://img67.echo.cx/img67/5605/badcarb22sp.jpg

For our viewers at home, that's a strange yellow-green goo, somewhat
watery. This was in cylinder #1, the one that wouldn't fire at all.
Also, all the jets look rusty. Could water have gotten in and started
growing stuff? Or are these just crazy deposits, and the green is
chemical (instead of mold or something)? Next, the other carbs:

http://img67.echo.cx/img67/2250/badcarb48cf.jpg
http://img67.echo.cx/img67/8012/badcarb51ee.jpg

These show what I'd call tapioca with chili powder. Some clear-ish goo
that looks (and feels) like jelly, covered in a rust sauce. Why are
all my analogies food? Don't know.

Another missing piece was this:
http://www.motorcycle-forum.net/tec...nalyzer_to_set_idle_mixture_screws_61320.html
"...in the idle jet, also called a pilot jet..."

So the idle jet = pilot jet. My Chilton's manual didn't show an idle
jet, but I found the "pilot jet" in a diagram. I took those out and
examined. Had to compare them to see what's wrong, since the outside
looked nice and shiny. It's a very skinny/long brass tube with holes
up to the tip, like a toilet roll that's fought with a hole-puncher.
That looks all good. But staring at it head on in the light shows a
very small hole for most of them. It should be (I assume) a hole the
diameter of the tube itself, but on mine they're just a pinprick. Like
arteries clogged with cholesterol. And cylinder #1? No hole at all...
completely blocked.

Go Krusty! Right on about the blocked idle jet for cylinder 1 (and all
of them being dirty = rough runnings). You gave me the hints, help,
and encouragement to pull it off and see what's wrong. I love working
on this stuff now! I'll soak the jets (and other non-rubber/plastic
parts) in the cleaner a bit, get rid of some of the rust/gunk, then
slap it together and see if it runs well now. Could still be some
other crap floating around, but looks like at least this needed to be
addressed. Krusty, you live anywhere close to Hawaii? I owe you a
beer (or your gratitude of choice).

One minor question: can I use the B12 chemtool to soak the jets? Or
should I keep the very large 1 gallon of Berryman's Chem-Dip (carb and
parts cleaner) and use it instead? (Otherwise I'll return it) How
about walmart-brand "carb cleaner" aerosol?

(Props to ImageShack, http://www.imageshack.us, for the free image
hosting... which will probably end up as broken links later on)

 

Also, Matt: if cleaning the jets/carbs brings back the smooth running,
I'm going to throw Chemtool in there and ride the carbon out of
cylinder 1 (might not even be worth worrying about). I'm curious about
Krusty's water cylinder-carbon cleanup method... usually water in the
gas is a bad thing. How would you go about it for carbon cleanup?
Intentionally contaminate your own fuel (ie pour some water in?)
Apologies if it's in that other post, I read it but I am a bit tired.
Thanks all.

 

Notice that the float bowl gasket has a little square extension in the
corner and there are two tiny little ports that are sealed off by the
square extension that
acts as 2 o-rings. Be sure to squirt aerosol carb cleaner through those
holes until it comes out wherever they go...

If you've ever been in a limestone cave like the ones at Carlsbad
Caverns, you've seen what strange shapes calcium carbonate can take.
Mix it with rust and copper salts and you'll have same weird colored
blobs, for sure...

How does water get in your gasoline? When you wash the motorbike is one
way. I always tape over the gas cap and the ignition key when I wash my
machines. It's a good idea to cover the handlebar switches and the
instruments to keep water out. Corrosion is the enemy of all things
electrical...

If you have water in your carbs, you probably have water in your gas
tank, and if you don't clean the water out of the tank, it will find
its way back to your carburetors. Water is bad stuff in a gravity fed
fuel system, it just won't sit peacefully in the bottom of the tank
like the water in your car's gas tank...

Your petcock probably has a filter on the standpipes inside the gas
tank. Register @ www.partsfiche.com and look at the fuel tank fiche.
Also check the carburetor fiche to see if there's a tiny fuel filter in
the carb above the float valve. You can clean out your tank and these
filters with fresh gasoline, but an aerosol carb cleaner like B-12 or
STP or Gumout carb cleaner will contain xylene and acetone that will
dissolve gum and varnish...

What it is, one of your buddies squirted some Heinz Ketchup into your
gas tank. He knew you'd laugh when you saw what he'd done ;-)

Don't get any bright ideas about reaming those holes out until they are
the same size as the inside diameter of the tube. They are precision
drilled holes, so if you have to use a fine needle to poke them out, do
so VERY carefully. The orifice hole in a pilot jet is only about 0.35mm
to 0.45mm. That's only 14 to 17 *thousandths* of an inch. The larger
cross-drilled holes are air emulsion holes
that mix air with the gasoline so the idle mixture is more easily
burnable. Carbureted air and gas make the finest mist possible, even
finer than what a fuel injector can do...

I live on the edge of the San Joaquin valley, right where the foothills
of the Sierra Nevada start. I accept the offer of a cyber beer...

B-12 Chemtool is fine for soaking carb parts. It will cause rubber
parts to swell up, but they will return to their original size when
they dry out. If the part is old and deteriorated anyway,you can't
blame B-12 if it crumbles and falls apart...

Take the Chem-Dip back and get your money back. That stuff is
NASTY-smelling. It contains smell cresylic acid that will stink up your
garage and your wife will get angry from the porta-potty smell on your
hands and clothes...

If you had some old Stromberg 97 carb that had been covered with grease
and gum and varnish and had sat around for 50 years, you might use
Chem-Dip, but it's just too thick for the tiny ports and orifices of a
motorbike carb...

I've used the Walmart stuff. It worked good. But the liquid B-12 in the
15-ounce can is handier for pouring into the gas tank...

 

The water is NOT added to the gasoline. If you did that, water would
separate and sit in the bottom of your gas tank and float bowl, unless
you added alcohol to the mixture. Alcohol will grab the water and blend
with it and some of the water would go through your engine and come out
the exhaust pipe as steam. But the some of the water might stay in your

gas tank to rust it out internally, and some of it might plug your jets
up again...

No, the water used for decarbonizing an engine is sprayed in the finest
mist possible into the bell mouths of the carbs while the engine is
running at around 5000 RPM or more...

You can use a Windex bottle to spray the water, but, if you do this
procedure, you take all responsibility for whatever happens when you
rev up the engine in idle. The water could condense into droplets, and
if you used far too much water, so much that the combustion chamber was
flooded with water, you might hydraulically lock the piston for just a
split second and you could bend a rod. So don't go crazy with the water
sprayer..

A motorcycle engine will gain RPM very rapidly when you rev it up out
of gear. Don't go crazy with the throttle when you're in neutral...

One time when I was steaming the carbon out of my GS-1100 Suzuki, I was
revving up the engine and watching great clouds of carbon fly out the
exhaust port as I blipped the engine up to 10,000 RPM and I heard the
bolts that held the starter clutch onto the alternator rotor snap...

 

from http://www.wqa.org/sitelogic.cfm?ID=472

I have to object to the idea that calcium carbonate deposits in the
carbs can come from water introduced into the fuel. There just isn't
much of it in the hardest water. I agree that water can cause various
kinds of corrosion in a carb. Maybe water could extract lime or other
salts from fuel ... doubtful ... I expect that the substances are mainly
1) oxides of copper, zinc, aluminum, magnesium, iron, etc. that come
from metal parts reacting with water, and 2) organic junk (polymers,
varnish) that settles from the fuel.

 

First he should as you suggested to me just run it in a low gear at high
rpm. Before I did that I could reach through a plug hole and scrape a
crust of carbon off the top of the cylinder. After I did it I could
look into through the plug hole with a flashlight and see the top of the
cylinder shine.

 

Current update: the bike is a runnin! The story: after cleaning, I put
the carbs back on, primed the gas, then started it up... and nothing.
Did a lot of starter tries, with choke, without, etc. For about 10
minutes tried off and on while checking things (with freshly charged
battery). Then with choke on, one cylinder started trying to fire with
the starter... kept going, finally 2 cylinders started going at it but
wouldn't run without the starter. Then bang, they all started going.

At first it was rough, same problem as before (more-throttle =
coughing, engine dying). For the first minute it was real jerky, kept
doing that wheeze thing (where it periodically sounds like "pshht",
like a blow off valve, and jerks back and forth). After a minute, the
thing started acting normal. Out of gear, the rev's went fine up to
4-5k (didn't check too much, bad mufflers and sleeping neighbors). In
gear it accelerates fine, I can finally feel the power back (before it
wouldn't go past 5mph in first).

The initial running made me think the problem was still there, but
after riding for 10 minutes the bike feels almost normal. It seems
like there's only a few things left. Will that "wheeze" sound come
back, and what does it mean? Is it normal cold starting stuff? And at
3-4k in gear there's a heck of a lot of vibration (the fairings are
rattling). Before I had thought it was due to the dead cylinder, but
all cylinders (I think) are firing now. What else could it be? Some
kind of bad balancer shaft or somewhat?

Super thanks again to krusty. There's prob water still in the tank,
and I can see some rust flakes on the bottom, so next is to empty out
the tank and clean it (and hopefully treat it). I'm running on "ON"
which pulls fuel out of the middle of the tank (with a screen), so I'm
hoping I'm not picking up any crud when I run for now. I'm going to
ride it a bit after tank cleaning, (maybe with chemtool, maybe not) and
then check out the 1st cylinder grime. Now that it's firing, seems
like it should clear itself out a bit.

Krusty, I'm trying to send that cyber-beer thing, but I can't figure it
out. Do you want 10010111001 beer, or 00101100111 beer? They also
have 100101110 Lite, but that pops up a "please register this beer for
$10" every time you take a sip... stupid shareware.

 

I don't suppose you've drilled out the EPA anti-tamper plugs and
cleaned out the holes that the idle mixture screws go into. B-12 in the
fuel should eventually clean those tiny little idle ports out, but, if
the crud that's blocking those ports is rust instead of varnish and
gum, you may eventually need to pull the carbs back off and do the the
whole EPA anti-tamper plug removal bit. I've described the process
about a bazillion times, just google for "[email protected] +EPA"

As to dificulty in starting and the cylinders firing up one at a time:

When your carb is totally clean inside and the idle jets are set right
and the idle speed is set right, you won't need to twist the throttle
grip to start the engine. You can just pull the choke knob all the way
out, or put the choke lever in the fully on position and the engine
should start up easily and run...

I've explained about a bazillion times that modern Japanese motorcycles
don't have real chokes with plates like a car, they have a starting
enrichener that is just a bypass port, a tiny little carburetor built
into the side of the main carb. If an owner notices that his idle speed
is getting lower and lower, but doesn't realize that's because his
carbs are getting gummed up, he will adjust the idle speed up. Then,
when the
idle jets are really too plugged up for the engine to run, the starting
enrichener won't work right, because the throttle butterflies are open
too far and there isn't enough engine vaccum downstream of the slightly
open butterflies...

The engine probably "wheezes" because it's not getting enough gasoline
under those conditions. One of the first things old British bike owners
learned was if they wanted their motorbike to start from cold was to
turn the idle speed knob all the way down to close the throttle all the
way so the engine would have enough vacuum to suck gasoline out of the
float bowl...

You'll find that there's a master idle knob on your carbs, and anytime
your motorbike has been sitting for a few weeks without being ridden,
turning it all the way counterclockwise will help when you try to start
the engine. You will have to open the throttle manually to keep the
engine running once it starts. Then you can readjust the idle speed
when the engine is warm

Fuel was just starting to flow through all the circuits for the first
time since you laid the motorbike up, so the engine ran rough...

No, it's not normal. It's just symptomatic of fuel starvation...

The engine is probably running rough...

Are the vacuum slides moving freely? They have to lift up for the carbs
to go through the off-idle transition and into the mid range. Just
spraying a bit of carb cleaner at the slides and pushing them up with
your finger is usually enough to solve the stuck slide problem...

The off-idle transition occurs when the butterflies open just enough to
uncover the idle bypass ports. Then vacuum lifts the slide and the
tapered jet needle comes up out of the cylindrical brass needle jet.
The diameter of the needle jet hole affects mixture richness and there
is still supposed to be mixture coming through the idle jets...

The cylindrical brass needle jet may or may not have air emulsion holes
drilled in it. These air holes can get plugged up if there's a lot of
crud in the float bowls. If the air and gas can't mix in the needle jet
the engine gets droplets of gasoline that are too large and the fuel is
hard to burn...

Needle jets will push up through the carb body, or down towards where
the float bowl goes. You might want to look at the carburetor parts
fiche on www.partsfish.com to see if you can figure out whether you
have the needle jets with air emulsion holes or not...

The needle jet hole size controls the mixture up to about 1/2 throttle,
then the tapered jet needle controls the mixture to about 3/4 throttle.

Finally, at 3/4 to fully open throttle, the main jet size controls fuel
flow. But the idle jets have been supplying an ever-decreasing amount
of fuel to the total mixture as you open the throttle...

The further the throttle is open, the less vacuum is available
downstream of the throttle butterflies and less idle fuel flows. But
you should be able to see that an engine equipped with constant vacuum
carbs such as you have really *needs* enough of that idle mixture fuel
to make the engine run just right at higher engine speeds up to near
wide open throttle...

So, I suspect that you still have some crud in the idle jets, the idle
ports, or around the idle mixture screws that are hidden under those
EPA anti-tamper plugs. Engines that aren't getting their proper fuel
amount will "wheeze" as you described...

 

I had the bike running but I tried to replace some screws in the carb
and now it's not. Fuel is getting to the float bowls, it ran on
starter fluid for 1 second, but trying with normal start doesn't work.
The EPA plugs were not present, though I think they should be on my
model. The mixture screws were set at 4.25, 3.58, and 4.5 turns out
for cylinders 4, 3, and 2. The screw for number 1 was stuck, you can
see it's been stripped a bit. It'll turn in to where it seats and
stop, then it'll turn out (stiffly) to about 2 turns out and stick
again. Why would this be sticking?

This seems a bit much, as the initial setting for my bike is 2 turns
out. Maybe to compensate for dirty pilot jets? (Read krusty's
previous posts on that). Idle jets are clean, all of the jets
actually. All the side passages I know of are good, jet needle (the
thing attached to the slide?) has no holes. I searched for
[email protected] +EPA, but didn't find the complete post yet (just ones
mentioning what to search for). I'll spend the 10 minutes tomorrow to
find that post. Should I take the carbs back off and clean the mixture
screws? What's the quickest way to get this bike at least starting?

In other news...
I took the tank off, lots of rust inside. As a temp measure I rinsed
it out a bit to get rid of some of the loose particles. The petcock
has had a slow leak in the "On" position (vacuum operated, on reserve
prime). I drained the tank and opened up the petcock, front and back.
Front side had a flake of rust blocking the fuel passage. Lots of
white/green powder, caked on. Used carb cleaner to get rid of all
that. On the front side there's an o-ring then a happy face looking
gasket, more plastic than rubber. That had scratches from the sediment
buildup. I turned it over to use the other side that was still smooth,
cleaned out all the crud. Now when I turn it to "on", no leak. Seems
like the sediment had built up on the valve (the part that turns), and
that had acted like sandpaper and worn away the gasket underneath,
until it could never completely seal the passages (hence the slow
leak). Turning the gasket over used it's good side and stopped the
leak. Woot.

 

Like I said in the other post, you can turn the master idle knob all
the way counterclockwise to fully close the butterflies and increase
vacuum at the idle and starter outlet ports. Or you can hand choke each
carb while cranking the engine to draw gasoline into the ports...

Joe Shadetree was messing about with the old pilot screws, eh? If the
pilot screws have to be turned out more than 3.5 turns, the idle jets
are too small. Joe Shadetree usually messes with the EPA plugs and the
idle mixture screws after he's pulled the air box off and installed K&N
filters. The irony of that is when there is less air filter
restriction, CV carbs will run a little richer at idle...

Joe Shadetree forced the screw to turn when it was all gummed up with
mineral salts and varnish? Is it just the soft brass screw that's a
little stripped? You can buy a new screw. It will probably come with
spring, washer, and o-ring as a set. The aluminum carburetor body is
made of aluminum that's a little harder, but the aluminum is alloyed
with
zinc to make it flow better so it can be die-cast. It's not as hard a
sand cast aluminum. If the threads are buggered, replacing the carb
body will be expen$ive

The jet needle moves up and down in the needle jet. The needle jet is a
large round orifice in a brass tube that is sometimes called the needle
jet holder. The main jet screws into the bottom.

The needle jet holder may have small cross-drilled air emulsion holes.
The emulsion air holes mix air with the gasoline to make finer droplets
than occurs with the non-emulsion type needle jet holder. The
non-emulsion type is called a "primary" type. The needle jet holder
with emulsion holes is called an "air bleed" type.

The needle jet holder can either be pushed down out of the carb toward
where the float bowl goes, or up through the area where the vacuum
slide goes.

Been there, done that. It's a temporary fix until the next time the
owner tries to turn the petcock lever while the petcock is all dry from
the gasoline in the front side of the petcock having evaporated...

 

I guess I had trouble figuring out the "master idle screw". I found a
stop screw, that determines where the rotating throttle thing (sorry)
rests when you release the throttle. Then there's the mixture screws.
Should I be looking for something else? I'll check again on my manual
when I get home, but I couldn't seem to find anything else to adjust.

If it's that stop screw, I think it's mostly out (counterclockwise)...
I'll check again.

 

Yes, the "rotating throttle thing" is a cable quadrant, and the thumb
screw that stops it when you release the throttle grip would be the
master idle knob. It opens both carbs at once...

 

It opens both carbs at once...

All 4 carbs. As soon as I get off work I'm going to mess around
with that screw.