[TR] TR4A - Balancing Carbs Oddity

G.D. Huggins guy at genfiniti.com
Tue Jun 4 16:06:12 MDT 2013


Greetings All,

I've recently found myself with some free time, and am looking into those low
priority items on my punch list.
First up is trying to get my engine to purr, as I've always had a rough idle,
with the RPM vacillating over a range of roughly 125, but smooths out while
driving.

I believe the issue might be indicated by something odd with my carbs (SU
HS6), which I had rebuilt by Paltech.
Here's the scenario..

I am using a Uni-Syn tool to balance the air flow (main idle).
The weird thing is that I achieve balance with the front carb's screw not
touching at all (therefore the throttle is not opened at all), and the rear
carb's screw is engaged (thus opening the throttle).
If this is correct, it means I am getting air flow balance from one carb
completely closed, and the other partially opened, which should not happen.

I'm planning on checking for a vacuum leak, and hoping I find one.
Is there anything else I could look for?

Maybe the throttle in the front carb is NOT closing all the way, even though
the idle screw is not engaged?
Maybe the cylinders aren't creating an equal amount of vacuum?

Thanks in advance!!



Cheers,

Guy D. Huggins
1965 Triumph TR4A
CTC 63569LO

Online project diary at http://www.genfiniti.com/triumph


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