The Lake Injector

THE LAKE INJECTOR

It's Simple And Ingenious. But How Does It Work?

CARBURETORS and other fuel/air mixing systems as a rule require a certain amount of complexity. The problem is that it is almost impossible for a simple fuel metering system to provide an optimum fuel/air mixture over a widely varying range of intake velocities and manifold pressures.

The Lake injector therefore must arouse some suspicion. It is simple. There is no float bowl. No jets to change. It has fewer parts than the trusty old A mal Monobloc. So how can it possibly work'.’

It works because the idea behind it is complex, yet the execution is simple. The Lake injector, a variation on the Gardner carburetor, is modular in concept. After choosing the proper throat size, the tuner may modify the Lake with different cutaway openings, and vary intake tract length by removing four screws and swapping bells of different sizes. Varying intake tract length and cutaway opening to bring out the desired pulling characteristics of an engine and match it to the intended use is no new idea. But the fact that the modular Lake design simplifies this task is new.

The metering system consists of a fuel induction pipe, a fiber slide, and a tapered needle inside the induction pipe. As the throttle is twisted, a cable raises both the slide and the induction pipe. As the slide is raised, more and more air is allowed to flow through the intake tract. At the same time, the induction pipe slides upward to progressively uncover more and more of the stationary needle's taper, thereby increasing the flow of gasoline (fed by gravity from the fuel tank).

Regulating the fuel/air ratio is accomplished in a novel fashion, tor the tapered needle serves to adjust the mixture for both high and low speed operation. The taper may be moved upward or downward by screwing the needle in or out of the injector body by turning the knob at the bottom of the injector. Raising or lowering the needle in this fashion, which requires several lull turns of the needle knob, “tunes” the injector for high speed, full power operation.

Once the basic up-or-down position of the needle has been established for the wide open throttle setting, then the direction in which the needle taper faces may be changed to alter fuel flow at partial throttle openings; this is done by rotating the needle adjustment within less than a half turn. Varying the position of the taper face in relation to the incoming air flow causes subtle changes in the pressure wave around the needle, and thus varies the amount ol fuel entering the intake tract at partial throttle open ing.

An advantage ot being able to adjust the Lake injector externally is that the rider may compensate tor altitude and barometric changes as they occur, without having to stop and fiddle with a box of jets. As the fundamental design allows changes in intake tract length and slide opening, the Lake may be adapted to a variety of uses motocross, TT racing, flat track, drag racing, road racing or just plain street riding.

AMA flat track and IT rider Paul Bostrom has successfully demonstrated the applicability ot the Lake to his sport. He mounted a pair ot them on his 650-CC Triumph racer. His machine runs quite well at the top end, but, more importantly, the bike pulls smoothly out of tight corners at low rpm. Bostrom, who represents Lake Research and Development, claims that the injector flows more air than most other fuel mixing instruments ot similar size, thus increasing power.

But the Lake injector may not be the answer for everyone. One that was mounted to a Bultaco motocross machine gave excellent full throttle power, but provided no improvement in lowend performance over the standard carburetor. Part of the problem is that it would seem to require a tuner's knowledge to choose the appropriate bells and tract lengths to suit the rider's needs. As the Lake costs $5 5 per unit, the gain in performance to the average street machine would not merit the cost for many riders.

However, for the competition rider or the mechanically inclined enthusiast who wants to experiment a bit, the Lake injector compact, simple to an extreme, novel in concept is an intriguing instrument with many possible applications. [Qj