Randy's Cycle Service Explains Carburetors, Choke & Cold Starting - vintage motorcycles. Randy's Cycle Service & Restoration in central Virginia USA. We service & restore all makes & models. We do not source or stock parts or sell vehicles. Technical advice starting at $25. Randy's Cycle Service & Restoration, www.rcycle.com
How Motorcycle Carburetors work and how to tune and clean them
Here's a link to the kind of carb cleaner I like best (it IS the best)
hey... awesome video..nicely explained !
just one question. Please do tel me wts AIR NEEDLE and LOW JET used for
again. ? i mean how and what do they work?
The air needle is like a transitional restriction to increase vacuum
pressure and tapered to prime the main jet flow gradually to ramp up fuel
flow from the idle/low circuit to the main circuit. Think of the circuits
like gears or stairs. The needle covers transition between 3rd gear to
about 5th gear on a six speed. It overlaps basically. Fuel is getting by
it from the idle/low- on through to where it's completely out of the way of
the main jet and the main jet fuel flow is roaring like the
Without the needle the carb would work, but not as smoothly through middle
throttle (where most people ride and have the most fine input or throttle
roll back and forth.
The low jet is like second gear on a transmission. You can shift from 1st
to 3rd, but again you risk stalling and it won't be as smooth. Also there
isn't really the mechanical inertia to carry the process on like you have
with a rolling vehicle with a flywheel on the engine and the wheels
turning. The pistons still create vacuum every other time they go down,
but air just doesn't have the punch that steel does when in motion.
The circuits in a carburetor have to be there or you would have a limit on
RPM range. An idle jet can't deliver enough fuel to really scream, and the
main jet couldn't go slow and would be VERY hard to start because the
engine would have to be spun up really fast. So you have usually four or
five circuits (I want to say jets, but their physically different) that get
air flow like stairs as the throttle opens. They are typically 1. Starting
circuit (choke on) 2. Idle circuit 3. low jet 4. Jet Needle 5. Main jet.
How Motorcycle Carburetors work and how to tune and clean them Check out
my other channel here http://www.youtube.com/watch?v=1KKvwMaIotA
How a carburetor works, schemes and explanations
This video explains, not in too much detail, how a 28mm Walbro diaphragm
carburetor works (using mainly schemes to point out what happens inside).
It explains what occurs at the venturi, what the butterfly valve is for,
how the needle doses the amount of fuel, and how does the diaphragm slide
Carburador Venturi Movil
Funciona operando el acelerador que directamente abre o cierra la cortina,
aumentando o cerrando el paso de aire - gasolina! Opera perfectamente en
motores de 2T en bajas y altas revoluciones, aunque en los motores de 4T
opera mejor en bajas revoluciones.
How a cv carburetor works. Sound of a YAMAHA XTZ750 Super Tenere.
basic carburettor adjustment (tuning) 4 stroke, and how it works.
In this part 1 of two video i am showing you where the different parts and
adjustments are on my old honda with a new carbie works on most small
carbies. i will show you what to look for when tuning your carbie! please
enjoy and watch my other videos. :D
i will make a part 2 tomorrow!
this one is on my honda xl100 1974 classic honda style, but is the same,
for classic and new yamaha kawasaki suzuki and all small bikes pretty much.
motorbikes and cars are simular. how to adjust the fuel air mixture and the
idle speed. riding it to test the tuning.
Motorcycle Repair: How to Clean a Motorcycle Carburetor
**Always follow the instructions in your repair manual when doing repair or
maintenance work on a motorcycle. Manuals can be found at the dealer and
Almost all motorcycle carburetors are slide type carburetors. Slide
carburetors can be further broken down to either mechanical or vacuum
operated. The vacuum operated carburetors are called CV or constant
velocity carburetors. The slides in a mechanical carburetor are operated by
the throttle cable and the slides in a CV carburetor are operated by engine
vacuum. Both type carburetors are very similar and are cleaned the same
way. Although care must be taken with the rubber slide diagram in a CV
If you choose to clean a carburetor with carburetor cleaner from a can, or
chemical cleaner in a dunk tank or gallon container, you must remove all
rubber and plastic pieces on the carburetor, or you risk ruining the parts.
A parts diagram for your carburetor will help you identify all the parts
that make up the carburetor, so you can remove the plastic and rubber
components before exposing the carburetor to chemical cleaner. Another
method of cleaning a carburetor that doesn't involve toxic cleaners and is
safe to use on all parts of the carburetor is a ultra sonic cleaner. Ultra
sonic cleaners are usually marketed as jewelry cleaners, but they also work
great for cleaning carburetors.
Carburetors have passage ways in the body of the carburetor. Some passage
ways are used as vents and some passages are used for the fuel circuits in
the carburetor. A motorcycle carburetor basically has 3 circuits if you
exclude the choke, and performance items like accelerator pumps. Every
motorcycle carburetor has a idle circuit, intermediate circuit, and a high
speed circuit. The idle circuit is responsible for delivering fuel from
closed throttle to about 1/4 turn of the throttle. The intermediate circuit
function from about 1/4 to 3/4 throttle opening, and the high speed circuit
is responsible for delivering fuel from 3/4 to full throttle. The circuits
are not limited to operating in this range, but they overlap and this helps
the engine to transition from one circuit to another. Identifying these
circuits in the carburetor can be helpful in cleaning the carburetor, but
it isn't necessary. The main components of the idle circuit is the pilot
jet and idle mixture screw. The main parts of the intermediate circuit is
the needle jet and jet needle. The main parts of the high speed circuit is
the main jet.
After you have all the components in a carburetor disassembled and cleaned,
its important to use compressed air to blow out all the passages of the
carburetor. I can't stress enough how effective compressed air is in
cleaning a carburetor. Sometimes passages in the carburetor don't get
clean from whatever cleaning method you use, and compressed air can be used
to blow out the obstruction. However, be careful not to blow out parts that
should be in the carburetor. A parts diagram will help to avoid this
After all parts of the carburetor are cleaned and all passage ways and jets
in the carburetor blown with compressed air, the carburetor can be
reassembled and adjusted if necessary.
Thanks for watching!