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 a cv carburetor works. Sound of a YAMAHA XTZ750 Super Tenere.
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)
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 to diagnose carburetor vacuum leaks on your motorcycle
This is a simple video demonstrating the best method to detect vacuum leaks
around your carb boots. Vacuum leaks are a fairly common problem in older
bikes, and luckily they can usually be remedied quickly and easily, the
first step however is diagnosis.
If your bike is running rough, won't rev up or has an irregular idle,
before you take off the carbs and open them up, check for vacuum leaks. A
vacuum leak occurs when too much air is introduced into the combustion
chamber via a failure in one or more of the carburetor boots or other
rubber mating surface. When too much air is sucked in, then the bike cannot
combust the gasoline efficiently; there must be an optimal ratio. Therefore
it is up to you to detect these leaks, and either plug them up or replace
the carb boots.
In this particular bike, the engine was running VERY lean. Not only did we
have vacuum leaks, but the baffles were taken out of the engine, and the
previous owner had removed the air filter and neglected to install a new
one. This is not only dangerous by allowing foreign material to enter the
engine, but it also makes the engine run much hotter, as lean explosions
create more heat than regular ones (think about blowing on a fire in your
fire place: more air, hotter fire). This can be detrimental to a variety of
parts in the engine, and it is a good thing we didn't ride this bike around
too much before finding the problem.
If anyone has any questions as to why this is important or how to
find/repair these leaks, leave a comment and I will respond.
How to adjust the jets on motorcycle carburetors
This is a brief introduction to the fairly touchy process of re-jetting
your carbs. The techniques discussed here are fairly universal to most
carburated motorcycles, but not all, so your first step in performing carb
tuning should be to consult your repair manual and online forums. Hopefully
this video can demystify a lot of the process for you, so that you have the
courage and interest to do this yourself. Let me know if you have any
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
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!
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