Date: Tue, 15 Jul 1997 10:53:29 +0200
From: Steinbeck Michael <Michael.Steinbeck@start.de>
Subject: TR4-SU-H6-fuel-pump-questions
Hi List,
I have a few carb questions.
My TR4 has SU H6 carbs and I had them just tuned by a professional
workshop. But still I am not sure if they did a perfect job. The car is
running better than before, but...
When I approach a traffic light or a stop sign I usually let the engine
slow down the car by simply getting off the accelerator and eventually
I push the clutch. The idle then goes down to about 400 rpm the
car starts shaking and the red light comes on (half of the time the
engine then dies on me) and after a few seconds (1 or 2) the idle
comes up to about 800 rpm and runs stable for any length of time.
This can't be normal.
This is not normal. Your carbs are definitely not well adjusted
or the problem stems from an electrical short on one of your spark plug wires.
One of the things that you want to check is that none of your spark plug lead
wires is
cut or burned, that the wire is fully inserted in the plug ends and that the
wire is not
shorting against say the heating tube that runs along the head. if a spark plug
wire has
an intermittent short it might cause the type of problem of irregular idle as
well as
lower than normal high end RPM. Escentially you motor may be running on only 3
cylinders
instead of 4. (you might want to check for a bad plug as well)
Furthermore I Still have a limitation in the max. rpms under load
(except it now goes up to about 4500 rpm). Earlier I wrote:
>It pulls through to about 4100 rpm and then it is quickly changing
>between acceleration and deceleration maintaining the 4100 rpm.
>My first thought was that the carbs aren't getting enough fuel, but
>now I'm thinking again if maybe the carbs should be adjusted.
>Here is some additional information: My TR4 has K&N air filters,
>an electric fuel pump and SU H6 carbs.
I got an answer by Bruce Clough (BTW, Thank you Bruce):
>Michael,
>Sound like a fuel delivery problem. Can it go beyond 4100 rpm at
>all for any length of time?
>Which electric fuel pump are you using? Do you use any type of
>pressure regulator in front of the carbs? Have you tried a stock
>pump on the engine to see if the problem clears itself up?
Here some Information on the fuel pump:
The electric fuel pump is by Mitsuba Elec. Co., Ltd. model FP-3 and
delivers a pressure of 0.3 kg/c^2. There is no pressure regulator in
front of the carbs (just a fuel filter) and I didn't yet try a different
pump.
And now my questions:
Are these two isolated problems or are they related?
As with all triumph reolated problems they may or may not be related:}
Did you check if your fuel filter is partially blocked or has maybe a possible
kink in
it that would restict fuel flow?
Can I perform the carb tuning myself?
Yes it is very simple for an twin H6 carbs. There are only two adjustments. One
for
throttle and the other for your jets. The throttle adjustment is located on the
left
Do I need a CO-meter to do the carb tuning?
no, what you need is an air flow guage and special carb wrench which you should
be able
to find at Moss Trf or Victoria British
Can the engine be seriously damaged if the carbs are out of tune?
yup, you bet
WHAT CAN I DO?
1) Determine if your problem does not stem from an intermittent short or a bad
plug. (If
that is what it is then you won't have to do the rest of this if the carbs were
already
adjusted properly by a pro)
2) get yourself an air flow gauge and carb wrench
3) remove your aircleaners
4) for each carb, turn your jet adjusting nut (the one under your carb next to
the jet
spring) all the way up to the top and then turn it down exactly 2 full turns
5) loosen one of the the carb throttle linkage bolts so that each carb throttle
turns
independantly
6)check for the telltale click of a properly centered jet by pressing the small
shaft
that protrudes on the RH underside of the carb body above the jet. by pushing
it in and
out you should hear an audiable click if you don't then you will have to loosen
the nut
that holds the jet assembly to the carb body and with the piston fully down,
retighten
the nut. (make sure that the piston travels all the way to the bottom and does
not stop
partway down)
7) start your engine and with it running at about 1000 RPM place the air flow
guage
against the opening of each carb and alternating between them, set your
throttle
adjustment screws so that each carb shows the same amount of airflow
8) re-attach your throttle linkage bolt so that both carbs are now working
together
9) Now it's time to adjust your jet mixture. Turn the jet nut 1 flat at a time
and using
a thin rigid wire, lift the carb piston about 1/8 of an inch. Turning clockwise
will
reduce air (lean) , counterclockwise increases air (rich). When the engine does
not slow
down or speed up after lifting the piston, the jet is set correctly. Set it for
one carb
and then the other
10) set you idle screws to proper idle ( I believe it should be 650 RPM but I
could be
wrong)
11) make sure that your choke linkage is properly adjusted
12 reattach your air filters
welcome
Barry Shefner
59 TR3A OTS 57675
jacad@cam.org
Thanks in advance.
Michael
1962 TR4, CT 17613 LO
michael.steinbeck@start.de
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