Common Tuning Issues:
We are confident that you will agree
with us that your new Mikuni carburetor is one of the best modifications
you have made to your Harley-Davidson motorcycle. The Mikuni
substantially increases power compared to the stock carburetor.
However it is the dramatic improvement in throttle response that
makes the Mikuni flatslide HSR carburetors such outstanding performers.
No carburetor made today can match the Mikuni in this regard.
We have chosen tuning components that, for the great majority
of applications, are correct. Chances are, you have had to do
very little beyond adjusting the air screw and idle speed screw.
However, a change to one engine tuning component often affects
or is affected by other components. All of these, the exhaust,
air cleaner, ignition, cams, etc., must work together if you
are to get the best performance from your Harley engine.
The current series of Harley-Davidson engines share many design
and therefore operational features going back at least to the
original Evo Big Twin of 1984. We and others have amassed a great
deal of information about how various tuning components work,
work together, do not work together or do not work well at all.
There is no one single combination of parts that is right for
all riding styles. The performance requirements of a touring
rider usually differ from those of the LTL (Light to Light) performance
rider. A combination of performance components that delivers
outstanding power ("Torque") in the middle range (2,000
to 4,000 rpm) seldom does as well above 5,000 rpm. The drag racer
usually could care less about what happens at 2,000; his/her
concern starts above 4,000 or so. These divergent requirements
are best served by somewhat different combinations of parts.
Except, of course, the Mikuni --- they both need that!
It is very difficult to put together successful performance parts
combinations without considerable testing and knowledge about
how these parts work and interact with one another. One can,
for instance, fit a camshaft design that favors top-end power
and combine it with an exhaust that restricts top-end power.
Such a combination delivers poor performance at both ends of
an engine's rpm range. Unfortunately, this sort of mis-match
Mikuni cannot take the responsibility of specifying all the possible
performance parts combinations that work together. However, we
may be able to help you avoid the general problem of "wrong"
combinations with the information found in the web pages assigned
to the links at the top of this page.