TONS OF CARBURETOR TECHNICAL INFO
Note:
We feel that exhaust systems can changed without rejetting to much.
Free flowing air boxes and pod filters will require jetting for sure.
The following tid-bits will hopefully help with your jetting questions.
But..........we could have two Honda's side by side for jetting.
Same air filters, exhaust system, ignition, altitude, color, tires and seat.
One Honda wants this jetting package and the other Honda wants a different
jetting package.
We feel ............ Carburetors are dumb, you need to tell them what to do.
If you spend any amount of time
around motorcycles, sooner or later you will run into issues caused by dirty
carburetors.
After completely disassembling, we
ultrasonically cleaned this set of carbs to remove all of the microscopic debris
from the carburetor surface and blind passageways that can not be accessed by
conventional means ( not only that it makes them look like new.) However,
if you don't have access to an ultrasonic cleaner this can also be accomplished
with a little effort, a can of carburetor cleaner, carburetor cleaning wire set
( K&L makes a nice one), some compressed air, and a lot of attention to
detail (but don't get depressed when they don't look as good as ours.). Be
sure to pay close attention to all of the small passageways.
Speaking of thorough cleaning, you will need to focus some attention on your needle seats. As we all know, bad gas will over time leave a film over everything that it is in contact with. We have found that a small piece of 0000 grade steel wool spun with a small screwdriver is the best way to remove this film and put a nice polish in your needle seat. By achieving this polish finish you will greatly reduce the risk of poorly seated needles resulting in fuel overflow.
Note:
This film that accumulates in the needle seat also accumulates everywhere else. Including the inside of your jets. This will obviously reduce the inside diameter of the jet resulting in incorrect or no fuel flow and delivery.
One of our cheapest ( about the cost of a twelve pack of beer for your friendly local machinist) and easiest carburetor modifications is to cut 0.007" from the flat portion of the slide bottom. This modification is most beneficial in instances where pod filters have been installed or serious air box modifications have been made. Refer to " More Carburetor Experiences " below for a technical description of why this is helpful.
Many of the above modifications and cleaning tips also pertain to later model carburetors. However, there are some major differences between the early and late model carburetors. With late model carbs there is the addition of an accelerator pump. It is very important to be sure that the rubber components of the pump are in good working condition. Gas over time has a tendency to deteriorate these parts. When this pump is not working properly it will result in a lean condition when coming off idle resulting in poor throttle response. Also, many of these later model carbs do not have adjustable needles. In these cases we use needle shims to richen the fuel delivery (the carbs in the picture have had two purple shims installed for a total of 0.040".) These later model carbs also have pressed in pilot jets. However, they are removable and we recommend that you do to ensure proper cleaning. By cutting the slides it is possible to make low end jetting adjustments that can not be made with the non-replaceable stock jets.
Poor mans jetting kit
This extra gas circuit procedure
has been done for years.
Carburetor jetting is an on going topic of discussion.
So, here is what we do from time to time.
Tap into the float bowl and insert pilot jets into the throat of the carburetor.
This procedure will give your bike a boost from approx 1/4 to full
throttle.
Also, it will allow you to check your float level at a glance and purge unwanted
sediment from your bowl.
Kit includes
Drills.
Taps.
Jets. ( 2 sizes )
Fuel fittings.
Fuel line.
Part #
Boosty 101
$ 59.95
Or, do it yourself if your so smart !!!!!!!!!!!!!!!!
Comment:
I do not see how this extra gas circuit would help anything. I would believe the
Honda factory did all the testing and came up with best system.
Answer:
I hope we are talking about performance increases.
If so, Americans have always exposed design flaws and weaknesses in factory
bikes.
Why, because we like to go fast.
Performance products like big bore kits, big cams, oversize valves and free
flowing heads will require modifications that are not "factory"
designs.
Comment:
But, in theory it makes no sense.
Answer:
Webster"s dictionary says:
Theory............. the principles of an art or science rather than its
practice. ....... a conjecture or guess.
Look, we are just giving people options that worked for us from time to time.
Comment:
Seems to me, you are just trying to make a buck.
Answer:
What ?
Maybe you should go to .............. www. I drive my stock Honda to get
milk web-site.
Cycle X
Rebuilt
Carb Program
Procedures:
-Completely Disassembled for inspection.
-Ultrasonically
Cleaned.
This method is the only way to thoroughly clean the passages
which are often missed by conventional means.
-We have many jetting packages for high-performance, open air boxes, and free
flowing exhaust systems.
For example:
Extra gas circuits ( poor mans
version )
Extra gas circuits ( adjust on the
fly )
Cut slides ( instant throttle
response)
Air jet installation (
explained below )
Wide Selection of jets ( to fit your
specific needs )
Bench tested and bench synched.
Note:
In some cases it could be very difficult to jet or modify carbs for spot-on
performance when alterations are made, other
than stock.
( Turning screws, raising or lowering needle clip positions or possible jet changes might be needed. )
-Polished
Float Bowls ( for a little extra shine )
Prices:
Carb Rebuild (your carbs)
Ultrasonic cleaned, polished bowls and your choice of jets.
Parts and labor....... $ 275.00
Additional modifications:
Carburetor set with above mentioned
procedures. ( in case you do not have a set or yours are not rebuildable )
add $75
Cut Slides:
Cutting the slides will bridge the gap between pilot circuits and needle
position.
Generally used with free flowing air filters or engine mods. ( instant throttle
response)
add $39 ( per set of 4)
Poor Man's Jet Kit :
This extra circuit will give you a noticeable boost in a wider range of throttle
openings. ( approx 1/4 to full throttle )
Poor mans jet kit ( parts only )
add 59.00
Poor mans jet kit installation:
add $30.00
Porting carburetors ( set of four )
Another way to inexpensively extract more power from stock carbs ( works well
with poor mans jet kit )
add $60
Air jet installation :
What's that ???????? ????????????
Read below
Ever
wonder why some bikes run better than others with the same components?
Why does my buddy’s bike have this jetting and mine doesn’t like that jetting?
For conversation sake, lets assume (Never assume.) that both bikes are in the same condition, same electrics, tuned up, altitude, etc…. (Mileage unknown.)
Why do some bikes require different jetting?
Story:
We had a customer’s motorcycle that began to run rich. All the normal tune-up stuff was ok. He is the original owner and no changes were made. (Exhaust, fancy air filters, etc.)
Question: So
why does the bike run richer? Failing ignition? Dirty
air filter? Float malfunctioning? Bad
fuel?
Answer: Worn carburetor needle jet and needle.
Just like pistons, carburetors are working hard. Slides are moving up & down, being pulled & pushed with intake pulses constantly wearing the inside of the needle jet.
The needle jets and needles are very precise and wear is immeasurable. The detection of this problem is sometimes difficult. (Unless you spend a $100.00 per hour on a Dyno.)
When you drive
a bike at normal speeds, you are generally in the pilot circuit, slide cutaway,
needle jet and in the needle a bit. These circuits work together delivering fuel
to your motor. A little wear in the needle jet and needles is why some bikes
with open exhaust, open air filters SOMETIMES run better with almost stock
jetting. We wrote a tech article on exhaust systems and tuning and basically
said: Select an exhaust system you like and jet accordingly with an open mind.
Same with this needle jet, needle topic: Do not go into jetting a bike with a
preconceived idea about jetting. Keep an open mind.
We do not know if needle jets & needles are still available or if you really need them.
This was just a
story and maybe this will help someday.
Here is what do from time to time.
Consider the needle jet like a drinking straw.
If you poked a hole in the straw, you would get a lesser amount of soda and a
bit more air.
In a carburetor, you would get a bit less fuel and a bit more air ( atomized
somewhat )
When the needle jet wears..............We install air jets so we can regulate
the amount of air entering the needle jet.
This is another "external " method to make these old carb's user
friendly.
Or.......... consider smaller air jets to strengthen the signal. ( more fuel )
Air jet installation:
Parts and labor $ 40.00 ( set of 4)
Honda cb750 DOHC High Performance Carbs
The testing is done
!!!!!!!!!!!!!!!!!
|
Jetting on the fly !!!!!!!!!
This extra gas circuit has many
benefits.
Completely adjustable external jetting system.
Delivers pre-atomized ( vaporized ) fuel for maximum horsepower.
Has enough external adjustability for any altitude, temperature or engine modifications.
Float levels can be checked at a glance.
* fast and easy tuning
* increases horsepower
* improved fuel efficiency
* quicker throttle response
* billet aluminum construction
* delivers pre-atomized fuel to the engine
* has no moving parts or electronics to fail
* compensates for altitude and temperature
This device is an advanced fuel circuit that may be adjusted manually through its precision needle valve.
This device supplies 10% to 15% of overall fuel in a pre-atomized or vapor state. It has its own fuel mixing chamber where air and fuel are properly mixed and per-atomized (vaporized). Fuel is drawn into this chamber from the float bowl, then united and swirled at high speed with air from the air correction circuit, thus vaporizing the fuel. This vaporized fuel is then inducted into the carburetor. This fuel weighs only 10% of what raw fuel weighs. The light weight of this fuel charge allows quick response to slight changes in engine fuel demand (engine load). You will have quicker throttle response, a broader power band, improved fuel efficiency, cooler running engine, longer plug life and excellent burn down protection. The fuel induction is controlled by engine vacuum, air flow, and acoustic sound signal,. The heavier your engine is loaded the more fuel this device feeds. When engine load decreases, so does this device's fuel flow.
You now have a demand feed fuel induction system that feeds fuel linear to engine load.
External jetting system ( Honda
twin carburetor system )
# CA 002
$229.00
More carburetor experiences
A lot of literature and chat room posts are helpful in diagnosing ill running motorcycles.
We wrote a tech article on ageing and worn needles and needle jets recently and talked about how aging components can mess up the diagnostic process. We prefer to write about running issues that are not in print or rarely talked about. Generally, these things have baffled us in our service department and are experienced real life fixes.
When it comes to carburetors and jetting, the diagnostic problem must be cut in half.
Is it rich or lean? At ¼,½, ¾, full throttle is it rich or lean? Many publications and discussions can help with this.
Here is a real life story and an experience that has worked for us from time to time.
When cruising down the road your bike is normally running about 2 ½ to 3 ½ thousand rpms. Most of the jetting conversations talk about pilots and needle positions. We feel that is a wide range. Why? There is a sweet spot that is overlooked when transitioning from pilots to needle position. ”The slide cutaway.” Sometimes with pod filters, drag pipes and other custom products you must have a determination to get the job done. Rather than, “I’ll live with its attitude.”
First, pilots, cutaways, needle jets, needles and main jets work together. They cross over, overlap, and need to be delivering fuel and air as needed.
Oh yea!
The cutaway!
The sweet spot!
Here is what we do in many high performance or aggressive situations. We will disassemble the carb bank and remove the carburetor slides. Then we will remove 7 thousands at a time from the bottom of the slide (On a lathe.) this will richen up the sweet spot (Between the pilot and needle position.), which is normally overlooked. Of coarse the carbs will need to be synchronized again for absolute determination of progress. Sometimes after doing this modification, we have gone back to stock pilot jetting. Here is the problem. This tip takes a lot of work and hours, but no money.
Sounds simple?
Some of these tips have cost us many hours in our service department and we would like to support people having annoying carburetor issues. Hope this helps someday.
** Note: Dynos are used with a 25% braking load to simulate heavier bikes that might ride with a passenger now and then. So, if you weigh 130lbs and you tune your bike perfectly then pick up a chick that weighs 250lbs your bike will need more fuel. So, if your bike runs great in neutral. But runs like shit on the road, give it more fuel.
