Mikuni Hsr42 Carburetor Kit
MIKUNI HSR42 CARBURETOR KIT
CW EVALUATION
Free breather
THE IMMENSE POPULARITY OF HARLEY-Davidson's 1340cc Evolution V-Twin has spawned a medley of aftermarket tuning options. Unfortunately, many modifications, like high-rpm-oriented camshafts and unmuffled exhaust systems, trade driveability and a quiet disposition for peaky power characteristics and excessive noise.
As an alternative, Mikuni (8910 Mikuni Ave., Northridge, CA 91234; 818/885-1242) offers its HSR42 Carburetor kit. Properly installed, the $395 kit is said to increase horsepow er and torque, and provide precise car buretion at all throttle settings.
The smooth-bore HSR42 features an eight-roller-bearing flat-slide throttle assembly with a 42mm venturi, an ad justable accelerator pump, a low-speed air screw and an idle-rpm adjuster. In addition to the newly developed carbu retor, the kit comes with a chrome air cleaner cover and airbox adapter, throttle cables and ties, extra jets, hose clamps and a 2.5mm Allen wrench. An eight-page instruction manual is in cluded, as is a list of required tools.
Replacing the stock 40mm Keihin carburetor with the pre-jetted Mikuni was a true bolt-on affair. To access the stock carb and its related cables, hoses and lines, Mikuni recommends elevat ing or removing the bike's fuel tank. On our long-term Dyna Wide Glide, sim ply raising the rear of the tank about 4 inches was enough. Removing the stock hardware-air-cleaner assembly, choke cable, vacuum and fuel hoses, throttle cables and carburetor-took less than 30 minutes.
Installing the new components was also simple. Routing the longer-thanstock throttle cables was the most diffi cult task, but once properly posi tioned and adjusted, the cables did not bind or hinder throttle control. Jetting was spot-on right out of the box. In deed, low-end and mid-range throttle response was wonderfully crisp, no ticeably improved over stock. At the dyno, though, our 49-state Dyna Wide Glide produced horsepower and torque curves nearly identical to stock. We did see a gain of 1.5 peak horsepower (53.7 compared to 52.2), but peak torque-67.2 foot-pounds at 3000 rpm compared to 68.6 foot-pounds at 2500 rpm-fell slightly.
To be fair, the HSR42 Carburetor Kit-available for 1990-to-present 1340cc Evolution V-Twins-was devel oped for use with modified engines. Used in conjunction with a mid-rangeoriented camshaft, uprated ignition system and a freer-flowing exhaust system, the HSR42 is said to provide a 6-horsepower gain. (Mikuni also claims a 6-horsepower increase for stock California models.) That's good, because throttle response alone is not enough to justify the kit's expense.
