Besides setting idle, you can confirm the SU's 'enrichment' system by blipping
the throttle. The flame should change from blue to yellow/orange briefly, then
settle back to blue when engine speed stabilizes.
--------------------------------
Bob Spidell - San Jose, CA
----- Original Message -----
I have used a Colortune for years, and it works just fine. For me, it has
been the only satisfactory way of tuning the SU carbs. According to the SU
manual, it is only necessary to set the correct mixture for an SU carburetor
at the specified idle speed. If the carburetors are working as designed and
the needles and springs are correct, the idle mixture is good for the entire
operating range of the carburetor.
If correct engine performance cannot be attained when the combustion flame
is a Bunsen blue, then there is probably something not right about the
carburetor you're trying to tune, since the Bunsen blue flame indicates
maximum efficiency of combustion.
About a year ago, I was trying to tune my MG Midget 1275 engine with the
Colortune. It had always worked fine in the past, but that time I could not
get the front carb to lean out from rich (yellow flame) to blue (correct).
I found later that for some reason the fuel pump was suddenly putting out
much too high a pressure at the front carb. On a 1275, the fuel line from
the pump goes to the front carb first.
Considering that the parts are mostly plastic, the only problem I have with
the Colortune is its high price.
Steve Byers
HBJ8L/36666
BJ8 Registry
Havelock, NC USA
Has anyone been successful with the Gunson Colortune on their Healey? I'm
considering buying one again. I had no luck on my MGB many years ago and
gave
it away but I have heard so positive about it recently.
Rich Kahn
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