ME 109 wrote:How much better (horsepower) is a mikuni over a 40mm bing? 5%? 10%?
Too many variables. The answer could be less, none, some –
or as many (horsepower) as other comprehensive engine changes will support.
ME 109 wrote:Does horsepower come into the equation or is it more a matter of responsiveness at given rev ranges?
Yes. Both. Perhaps.
Let's start with the assumption that BMW might have had good reason
to fit slide carbs (and not CD carbs) to the performance oriented R90S.
If there will be one truism about the Slide vs CD carb comaparison,
it might be that the slide can work very well as a performance carb, the CD typically does not.
As evidence of this fact, witness the popularity of Mikuni VM slide carbs on BMW Vintage Racers.
Elapsed time between wrist input and throttle response will be a primary consideration.
IF maximum HP output and torque delivery characteristics of a given engine are primary objectives,
one might rather pursue the path of detailed attention to intake/carb/head/exhaust matching and tuning –
rather than swapping carb type.
If coaxing that well built, matched, and tuned engine around the track
in the least amount of time possible will be the goal –
consider a slide.
ME 109 wrote:I don't understand why people want to squeeze an extra few hp from a airhead engine and still only have an engine with a third hp of what can be had in other bikes.
The problem will be in the expectation of a purely rational and objectively justifiable response.
None exists.
The answer might well involve the
feelings of "accomplishment & gratification"
that will be the result of focusing a fine machine's performance to suit one individual's expectations
as the direct and immediate result of that individual's personal and hands-on involvement.
In essence of quality, if not in quantity,
this might be the same motive that will make another BMW owner just so damn proud
of whatever doo-dad add-on that might distinguish his ride
from the thousands of other cookie-cutter models sold ...
Or, the answer might simply be: "Why not ?"
Note: I own and ride a 120-HP R1200S. I am also building an airhead that
might put down 80 ...
I suspect that the "joy" of riding that build will not be fairly described or judged on a dyno.
ME 109 wrote:I realise a lot more than a few hp can be gained by hot rodding an airhead but that's going to take some big bucks?
As anything the individual should choose to pursue in a consumer/capitalist society –
there will be a price to pay.
... and the law of "Diminishing Returns" certainly applies.
