Hi Folks -
Having trouble adjusting my SU carbs...
Some of you may remember that barbeque day at Mike Carion's place --
several people tried to help me solve a problem where at about 4-4.5k rpm
my roadster starts sputtering or backfiring through the carbs...
Anyway, the net result of that assistance was a much richer running
roadster. At idle, you could smell the gas, real strong, and while the
backfiring problem seemed to have gotten a little better, the motor still
misfired at a fast cruise. While at Shasta, it was running so rich that
it was almost impossible to keep running at idle for the run to the rocks
(at high altitude).
So I picked up an airflow meter and a Colortune kit. The airflow matches
between the two units, but I can't get the mixture right. My front carb
mixture will adjust so I get the correct light blue flame at idle. The
color stays the same light blue when I wind up the motor (colortune says
this is the correct behavior). The other unit, however, will not allow me
to achieve this light blue flame at idle.
I can only get a yellow flame (too rich) no matter what setting I put my
mixture screw at. Colortune says that this means I may have any of these
conditions applying:
1) leak at float needle or float needle out of adjustment.( I'm flooding
the carb all the time)
2) jet needle out of adjustment
3) worn needle seat
4) worn needle
I've checked for 1 & 2, I don't know how to check for #3 or 4. The needle
looked OK when I disassembled the suction chamber. I checked the float
needle and lever -- the needle sealed the valve when depressed, and the
lever measured per the specifications in the roadster manual (14-15mm
space between the top of the lever and the underside of the float bowl
cover)
I've called a couple people -- they said check to make sure the choke
isn't on all the time (checked and a-ok).
As far as the backfiring goes, another person said check the oil level,
your damper may be opening too quick and leaning out the rear carb. I
don't see how a low oil level could affect me at idle, but went ahead and
checked the oil anyway and the level was fine. Dampers on both carbs have
good resistance, and now that I've taken apart the rear carb's suction
chamber (had to pour out the oil), I know what a damper with a low oil
level feels like....
So anyway, anybody got some advice? Anybody want to take a trip over to
help out, and get some free beer and free use of a Colortune kit as part
of the deal? I'm reluctant to drive anywhere now, as I understand running
too lean can lead to burned exhaust valves (if I haven't burned 'em
already in my first 6 months on the road). I don't think I have burned
valves because I only have 3500 miles on a rebuilt 1600, and on my only
long drives (from CDM to Berkeley, and Berkeley to Solvang and back) I
didn't really push the car too hard.
Would messed up valves cause me to get these results with a Colortune kit?
Would inadequate compression cause a problem like this on the rear
cylinders?
I've read some web pages, particularly the SU tech tip page on Ross's
site. I'm hoping that adjusting the carbs will cure my problem instead of
having to do all kinds of measurement if my needles are wrong or worn, or
other things wrong.
thx for any help...
-Eric
'66 1600 w/a '68 5-main motor
Eric Armstrong
~~~~~~~~~~~~~~
phone: (510) 502-5984
e-mail: ericarm@alum.calberkeley.org
http://alum.calberkeley.org/~ericarm
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