gas in air filter?

I have a 2003 Kawasaki KLR-650 that I have modified by adjusting the idle
mixture screw on the carburator to 2.5 turns out (as is generally
recommended by KLR owners) and have also richened up the midrange by
shimming the needle. This is a California bike that was typically delivered
with very lean jetting.

I went to service my air filter today and noticed that the foam filter
smelled like gasoline. It wasn't drenched or anything like that, but it had
a strong gasoline odor.

The bike runs great. I can start it with little or no enrichener and it
warms up quickly. It will occasionally backfire through the exhaust on
trailing throttle but only occasionally and otherwise runs great through the
entire rpm range.

Is the odor of gas on the air filter something I need to be concerned about?

Ed Chait

On Apr 19, 3:06�am, "Ed Chait" <edchait4rem....TakeThisOut@earthlink.net> wrote:
> I have a 2003 Kawasaki KLR-650 that I have modified by adjusting the idle
> mixture screw on the carburator to 2.5 turns out (as is generally
> recommended by KLR owners) and have also richened up the midrange by
> shimming the needle.  This is a California bike that was typically delivered
> with very lean jetting.

Shimming the needle to richen up the midrange on a streetbike equipped
with *diaphragm carbs* is an urban myth perpetuated by people who want
to sound authoritative.

I tried moving the needle clip down one slot on *slide valve* carbs
that had adjustable needles and always went back to the original
position.

And, the actual position of the *jet needle* in the *needle jet* in a
diaphragm carb is controlled by engine vacuum, and that's dependant
upon the position of the throttle butterfly. If you open the throttle
too far, vacuum decreases, the slide falls, and what happens to the
needle that's attached to the slide? What happens to mid-range mixture
then?

Where does the extra source of gasoline come from at small throttle
openings? It mostly comes from the transition ports just downstream of
the throttle butterfly and the single idle mixture outlet port that is
adjustable by turning the idle mixture screw.

The idle mixture screw acts as a sort of "trimmer" on the total idle
mixture because the single idle mixture port is in parallel with the
three fixed transition ports.

You get 75% of all the gasoline your engine uses from the idle jet
until the slide rises far enough for the area of the *variable*
orifice created by the jet needle/needle jet to be larger than the
*fixed* orifice which is the hole in the main jet.

Read what Mark Salvisberg has to say about CV carb tuning on www.factorypro..com.

Most newbies have the idea that their engine suddenly gets a big shot
of extra gasoline when the carburetor goes onto the main jet.

That's just not true. It's bass ackwards from reality. If the main jet
is correctly sized, it *limits* the flow of gasoline to what is
necessary to keep the engine cool when you ride at full throttle for
extended periods. And, what street rider ever does that?

I've had my KLR up to 90 mph for very short distances, and it starts
waggling and weaving and generally doing the high speed mambo, so I
slow down to 75 or 80 mph indicated, where it's a lot happier.
>
> I went to service my air filter today and noticed that the foam filter
> smelled like gasoline.  It wasn't drenched or anything like that, but it had
> a strong gasoline odor.

What does your oil smell like? Maybe your float valve is stuck open
and you're getting the gasoline fumes from the crankcase breather
hose?
>
> The bike runs great.  I can start it with little or no enrichener and it
> warms up quickly.

That indicates your idle mixture may be too rich. The starting
enrichener is NOT really intended to be used in any position except
fully open or fully closed. When starting, you should open the
enrichener fully, and leave the twist grip alone. The enrichener is a
little air valve in a passage that bypasses the throttle butterfly. It
sucks gasoline straight out of the float bowl through a brass tube
like a kid sucking milk through a straw.

If you open the throttle butterfly even slightly, vacuum drops off at
the enrichener outlet port and defeats it. But, if your idle mixture
screw is opened so far that you had to adjust the idle speed knob
higher, you're getting extra mixture through the transition ports.

You're the only one who knows the answer to the following questions.
Did the engine idle too slow after you opened the idle mixture screw
to 2.5 turns out? Did you turn the idle speed screw to adjust the idle
up? Does the engine sometimes idle far too fast for a long time after
you close the throttle when the engine is warmed up?

If you answered "yes" to those questions, your idle mixture screw is
turned out too far.

�> It will occasionally backfire through the exhaust on
> trailing throttle but only occasionally and otherwise runs great through the
> entire rpm range.

My KLR always farted out the exhaust on trailing throttle from the day
I got it. There is a vacuum operated diaphragm valve on the side of
the carburetor that is supposed to reduce air to the idle mixture
circuits on trailing throttle, but it doesn't seem to do much of
anything. These diaphragm valves are also seen on the carburetors of
metric cruisers, but the owners complain about backfiring in the
exhaust system.

A lot of the banging and farting in the exhaust system result from the
ignition system firing an extra "waste spark" when the exhaust valve
is open. If there is a lot of unburned gasoline in the exhaust pipe,
it's going to backfire.
>
> Is the odor of gas on the air filter something I need to be concerned about?

If your engine oil smells like gasoline, it's diluted and isn't
lubricating as well.