'87 CBR600: Lo-speed miss

Go to http://www.powersportspro.com/pages/parts/viewbybrand/default.aspx
and look at the second carburetor fiche. The idle mixture screws are
item #6

No, it has to do with the EPA emissions requirements. The idle mixture
screws were set as lean as possible at the factory and then sealed.

No, I don't. What is it in refernece to?

 

In the (Honda) CBR600F_'89-90_Service_Manual.pdf at http://stephygee.com/ :

Page 6-12 depicts "Air Injection Control Valve Removal, etc (SW, AR Type Only)".

Page 6-13 depicts "Pilot Screw Adj. (SW Type Only)".

California-only, p'raps?

P

" ... and the bees made honey in the lion's head."
- from "If I Had My Way", Blind Willie Johnson

 

That's an impressive site, but I can't find the pdf file by clicking
on the buttons.

 

You gotta wait for the flashy idiot garbage to settle down. Then look
for "89-90 CBR 600 F" on lower left and download. Then ya gotta unzip the mutha.

P

" ... and the bees made honey in the lion's head."
- from "If I Had My Way", Blind Willie Johnson

 

Those are the type codes for motorcycles sold in various markets. "SW"
is Switzerland and "AR" is Austria.

 

If nothing was done mechanically to cause this then I'd have to say
it's possible something inside the carb has worn out to create a rich
condition. Got any spark plugs showing a lot of carbon?

I had the same thing happen when my Charcoal Cannister screen broke and
filled the float bowls with charcoal. If your float bowls are completely
clean then I'd go with the above.

If you're looking for the adjusters, look on the right/exhaust side of
the carbs in the lower front corner of the carb. If the non tamper caps
are still on you will see a small grey screw head that will have limited
movement (1/4 turn max each direction). I pried the caps off to find a
smaller brass screw head underneath which was not limited in movement.

Check out Factorypro.com / Product Tech Support / CV Carb Tuning
section for some tips on troubleshooting lean/rich conditions.
I took my carbs apart for cleaning and played around with the throttle
needle height, pilot screw setting, and main jet quite a bit. Why? I
bought the bike with stock jetting and a Yoshimura full race only
exhaust already installed. Ran super lean I had a few flat spots I had
to dial out. I can go into more details on what I found/fixed, if you
need the info.
One indicator I used when I was tuning: If I revved the bike, and it
'hung' before dropping down to idle, then it was too lean. If it dropped
down to idle like a brick, it was too rich. Then I'd adjust the pilot
screw and needle accordingly.
I've got two ideas. 1) Something has worn inside the carb allowing too
much fuel to bog down the bike at those rpms. A float valve/leaking
jet/or even worn throttle needle 2) A few years ago my
Regulator/Rectifier melted and failed. I replaced it with a salvage yard
(yet good) R/R and a fresh battery. The bike never fired up/idled and
accelerated so smooth. After a few months, the stumble I had came back
to normal, and just last year my second R/R burned up.
As a side note, in the 15 years I've had it, I've had 6 batteries die.
I have an electrical issue I haven't really troubleshot yet (stator).
It's been a great bike otherwise.

-88 CBR600F 72k
-07 Victory 8 Ball 4k

 

Nope. Pulled #1 and 2 plugs not long ago. Looked normal.

The bowls were *extremely* clean when I pulled carbs last season. Bike
has had very little use since.

My bike is 100% stock and I got no evidence (via plugs) of a mixture
problem.

I've not noticed either condition.

Hmmmmm. Interesting.

Problem symptoms?

Back in the 90's it took po' me 2+ years to diagnose/fix an intermittent
elec. problem (failed to start at unpredictable times). It was the
pulse generator.

Thx,
P

" ... and the bees made honey in the lion's head."
- from "If I Had My Way", Blind Willie Johnson

 

The famous endings of Monty Python were: "And now for something
completely different"

It seems you have correct and clean carbs.
Maybe an IC igniter that has trouble timing low revs? I'd check
timing with a stroboscope.

Rob.

 

It's at least a possibility, if not a likelihood.

Alas, po' me lacks both the skill and the (stroboscope) device! :-(

Thx,
P

" ... and the bees made honey in the lion's head."
- from "If I Had My Way", Blind Willie Johnson