"650 V Stars "Custom, Classic & Dragstar"
Trouble shooting a rich or lean situation By MGD "Jeff"
Carb Diagnostics and Tuning
The instructions at the "CC&D webpage" performance section are excellent and
have been successful many times, but on occasion some fine tuning may be
necessary.
The riding style, accessories and total weight are areas that may need some carb
"tweaking"
Basic info
A rich carb setting will often exhibit the same drivability characteristics as a
bike with a lean
carb setting.....the mpg will be the only indicator unless some form of testing
can be done.
Pipes will change color if the bike is rich or lean.
A lean bike is easier to diagnose than a rich bike.
Choke Test
If there is a particular speed and gear operating zone, where you experience a
drivability
problem (example; surge, miss, hesitation) the
choke test can easily be performed.
While duplicating the drivability problem, pull the choke knob out to the second
notch. This
will richen the carb circuit you are operating in. If the problem improves or
disappears,
that particular carb circuit is lean. If the problem gets worse , then the carb
circuit is already
too rich.
(Do not do the choke test by leaving the choke on for an
extended ride.)
Tape Test For Rak AK
The tape test is similar to the choke test, or may be used with the choke test.
Tape is applied
(usually duct tape) over a portion of the inlet air supply opening. By
restricting the air flow
to the carbs, you can richen the fuel mixture. With the tape, you can cover
different percentages
of the inlet opening. The same results from the choke test apply. If the bike
runs better, then
it is lean.
The tape test can be effective if; you believe the bike is lean in most of the
carb circuits or
if you are working in several problem areas.
Remember, the tape test will make the bike rich in properly tuned carb circuits
or will richen
lean carb circuits.
Plug Test
Personal opinion, is a waste of time. Today's gasoline's has so many additives,
that it is hard
to get spark plugs to color quickly, unless the bike is rich.
Old spark plugs will color quicker than new spark plugs. Check the color on your
old plugs,
make jetting corrections, ride the bike for 20 miles then let the bike cool down
and pull the plugs.
Compare the old jetting color and the jetting color. Darker is richer, gray,
brown, tan...darker
is richer.
MPG Test
The bike is running fine. The bike is running perfect. Your mpg is around 40.
You are rich.
MPG is determined by dividing the miles traveled by the gallons of gas purchased
at a fill up.
The Canadians and Europeans will do kilometers and liters.
A properly jetted bike should be able to achieve high forties to low fifty
mpg.,unless you
ride like a maniac.
Rev Limit
Rev limiter points 1st 30-32 mph, 2nd 50-52 mph , 3rd
70-72mph, 4th 90mph
Wide open throttle to the prescribed limit points at which time one of the cylinders will shut down – (it will sound like it’s gonna blow up… don’t worry – it won’t). Hit the first limit point when the engine all of a sudden starts to run really poorly then shift to the next point. If you hit the rev limits at the right speeds or better, this is a good indication that the bike is jetted correctly.
Also see the Theory write-up, the Roll Off
test in
Webslingers Jetting info and the
Tuning and
Troubleshooting guide by Mikuni.