Carb synch CBR1000F

My idle is getting somewhat rough, so I thought I'd check the carb
synch.

But I can't find any vacuum nipples. Where the heck are they??

The bike is a 1996 Honda CBR1000F.

 

You have to buy them.

 

Bzzzzt!

What'$ up with carb $ynchronizing? It'$ a real money maker for
mechanic$ in $tealer$hip$. And the manufacturer$ of $hop gadget$ for
$ynching carb$ like the money they get from their naive victim$ (AKA
amateur mechanics).

I bought the cheapest version of Carb Stix I could find. Used it ONCE.

My carburetors NEVER need synchronizing. That was something that was
necessary for old Honda CB-750K models with multiple cable slide valve
carbs.

Modern engines have CV carbs or fuel injection, and what is there to go
out of adjustment on modern CV carbs if you don't ride 50K miles every
year?

Before you start screwing around with the carburetor synchronization,
why don't you do a fuel system cleaning with something like Berryman's
B-12 Chemtool Choke and Carburetor Cleaner.

Just put 4 ounces of B-12 into a full tank of gasoline and go for a
slow ride to make the carburetors suck the B-12/gasoline mix through
the idle jets.

When the engine warms up, you might discover that the idle RPM is a lot
higher than it was when you started out, so you can turn the idle knob
down.

If you live in a country where gasoline is called "petrol", buy a
carburetor cleaner that contains xylene, toluene, acetone, and methyl
alcohol. Don't use anything containing
"petroleum distillate". That stuff is for lubrication fuel injectors.

 

My owner's manual specifies carb synch every 12000km. Since the bike
now has 60000km on the clock, I'd say it's about time.

I simply do not have the knowledge and experience to second-guess the
guys who developed and built my bike, so I'll just have to take their
word for it.

They're not getting any money from me. I'd rather spend the money on
tools so I can do the job myself.

I'm planning on trying the plastic tube with a little oil in it.
Should come out quite cheap.

My previous bike's idle improved considerably after a carb synch. It
was almost 20 years old, though.

American brand names don't do me any good, but I have put in some
cleaning stuff. Too early to say if it has had any effect.

I call it "bensin". What do I buy then?

Thanks for your comments, FB.

 

Maybe. Most of the services specified in owners manuals seem to be
scheduled about four times as often as needed. I suspect that the
factory manual writers believe that the typical motorcycle is left
sitting out in the rain and that it is ridden on jungle roads or in the
desert.

After having owned 15 motorcycles and 25 cars, I have come to the
realization that most servicing of vehicles is a moneymaker for a
$tealer$hip and that the $ervice writer who greets you as you enter the
garage will try to $ell you anything you will buy. Oh, the stories I
could tell you about predatory mechanics and service writers.

Well, there is always the satisfaction be being an acolyte in the
Temple of the Immaculately Maintained Motorcycle and making
ministrations and sacrifices to the Metal God, and, if that's your bag,
enjoy it. You have my blessing.

Carburetor cleaners such as I described will clean out all the gum and
varnish blocking the idle mixture passages, if you ride through one or
two tanks of gasoline.
The cleaners won't touch calcium carbonate or metal salts from
corrosion though.

I don't suppose that you would find STP or Gum Out carburetor cleaner
wherever you live either. But the basic carburetor cleaner you need
contains xylene, toluene, acetone, and methyl alcohol. Those chemicals
can be bought in hardware stores too, in half-liter cans. Xylene is
paint thinner, toluene is used in plastic glues, acetone is fingernail
polish remover, and methyl alcohol is often sold as methyl ethyl
ketone.

Ordinary pump gasoline contains alcohols to clean out the passages in
carburetors.
I always noticed that my engine would run a little rough at the
beginning of a long ride if the motorcycle hadn't been ridden for a
month or two, but that it would start running smoother after the
solvents in the gasoline began to work.

 

How about if I use two U-hoses and then connect them at the bottom
using three T-connectors?

In my head, it works

 

Thanks for your comments, Pierce and Mark.

But I must be blind. I cannot find any screws that seem to be anywhere
near the right place. I just ran down to the garage and took a few
pictures:

http://roro.greatnow.com

(Sorry about all the ads. It's the price of free.)

The black caps have this suspicious looking "lip" that seems to be
about in the right area. Do I have to take these caps off to do the
synch? I'd guess the carbs won't work with the caps off?

I have a service manual, but it covers a wide year model range, and
all the carb stuff seems to focus on an older model. On that one,
there are simply rubber caps to pull off the nipples.

 

For ****'s sake., You post decent common sense for a month or two and
then revert.

It's also necessary for old 400 Fours, like I've got. And also modern
Triumph Trophy 1200s, like I've got.

Surprise me. The Trophy needs a balance about every 12k or it gets
harder to start and the tickover gets erratic.

Are you on commission from them or something?

 

Indeed. And if you get the connector tubes crossed, and thus connect
Number Three cylinder to (say) Number Two gauge, you can have endless
fun.

DAMHIKIJK,OK?

 

Is that all??? I reckon I've owned about 250-300 bikes. Not so many
cars, mind. Maybe a dozen, and most of them have been company provided.

There are, indeed, a lot of sharks out there. There are also some
fantastic dealers. Treasure them.

 

They are not on the inlet rubbers either, but I think I found them
now. I discovered that the petcock was vacuum controlled, so I could
simply follow the hose from there.

The nipples are placed directly into the cylinder head or the inlet
rubber flange, partly in the underside of the rubber. I've added a
couple of pictures to try and show one of them.

It seems I have to take off the lower fairing to get to them. I am due
for an oil change soon, which also requires removal of the lower
fairing, so I'll take a closer look at it then.

Thanks for your help.

 

I used a differential manometer on my 6 cyl CBX. It did a great job and
was mostly painless.

You still need the adapters and restrictors.

IIRC Honda used similar carbs on the CBX and CB1100f. The vacuum port in
located on the throttle body of the carb close to the intake manifolds
(rubber boots). It looks like a filister head screw but with a flat top
instead of oval. It requires the use of a flat blade screwdriver to remove
although I have seen a couple with philips heads. Depending on which side
they are, the screws should be at either the 10 o clock position or 2 o
clock position. Try not to lose the little metal gasket under the screw.
A screw starter is handy for putting them back in.

The vacuum port has to be between the engine and the throttle plate of the
carb. There is one base carb that is your reference. Every other carb is
adjusted to match that. Don't forget to get the right tool for the job.
You will likely need a special tool to adjust the carbs. Read the service
manual and what others have said about it.

 

(The Older Gentleman) wrote in

A clean carb is a necessity before balancing. If in doubt run some
Berryman's or Yamaha carb cleaner thru your fuel system before you do the
sync.

 

I've never used carb cleaner before a carb balance.

Over here, I dunno if Berryman's stuff exists. Ultrasonic cleaning is
the sure way.

 

(The Older Gentleman) wrote in

While ultasonic is a good method, it does require disassembly. The
chemical cleaning is sometimes all that is necessary. No sense driving in
a thumbtack with a sledge hammer.

 

True, true. But for *really* clogged carbs (like sitting-for-decades
carbs), I think it might struggle.

 

(The Older Gentleman) wrote in

A that point in time, the chemical treatment is likely a very long and
drawn out affair with very limited success.