Jumping back to Ted's post #13, I do have a few thoughts on that, which are related to some testing I did a long time ago on a Yamaha (yes: a 2-stroke, so admittedly, I have no first-hand knowledge if this would work the same on a 4-stroke).
I made a few different intake manifolds for a KT-100, and tested using a variety of carbs with progressively smaller venturis. I recall that the smallest carb had something like a half-inch bore in the venturi, so it was
really small. I did all my testing direct-drive, as I didn't want a clutch interfering with a pure engine test.
The first interesting discovery was that the smaller the carb bore was, the easier the engine was to tune (still have to have a fuel pump that can supply enough fuel for the demand, but since the airflow is lower, a bit less fuel capacity is required). The tuning results were dramatic enough, that I felt a half-inch venturi carb could almost be "fixed jet" on a KT-100. The other thing I found was as the bore in the carb became smaller, the exhaust pipe length became less "sensitive". (admittedly, a direct drive exhaust pipe is not as sensitive as the pipes we run with a clutch slipping at 10,000rpm). The other major thing I noticed was that engine still revved fairly well, pulled well down low, but the mid-range was "softened" noticeably. To me, this was an ideal characteristic to have, especially for newer people, because right where the engine pulls really hard is where tuning becomes critical, and also is the point in the rev range where engines tend to "hurt themselves".
The original impetus for this testing was to try to find something better than an exhaust pill, or a spec pipe, or an intake restrictor behind the carb, or lowering compression (I'm personally not a fan of any of those). A tiny carb seemed like a really good solution for something like a beginner or junior class... easier to tune (almost "set it and forget it"), and the engine ran well through the range, just with less power.
All this testing fell on deaf ears, unfortunately.
So back to Ted's point, and also referring to my post about the old "Stock Appearing" class in IKF -- I do (personally) believe that maybe a bit larger engine (displacement-wise) with a tightly controlled small carb can be a step in the right direction (and could still have as much if not more power than the "stock" out of the box engines currently in use). It's not the answer to everything, but I believe with some testing and experimenting, many (but not all) of the engine items that may be prone to "rule bending" might become a non-issue.
Anyone that has followed IMSA racing in the past years probably knows that BOP (balance of performance) is (was) *primarily* controlled by an intake restrictor. (yes, they do other things to like tweak the weights and adjust the amount of fuel a car can carry or use in a race). I'm not a fan of BOP racing at all, but intake restrictors definitely work, and in our case... a small venturi carb may be worth testing on various levels of engines to see how they respond.
my 2c..... which with another $3.98, may get you a cup of coffee at Starbucks.
PM
