Yamaha Seca Ii

YAMAHA SECA II

CW PROJECT

BARGAIN BLASTER MADE BETTER

MATTHEW MILES

YAMAHA’S SECA II is a true modern standard. It’s a stylish, full-size motorcycle with comfortable ergonomics, a freerevving, 598cc inline-Four and singleshock rear suspension. It is also priced affordably. At $3999, the ’93 model will conform to practically any budget. In fact, we were so pleased with the bike that we named it Best Bargain in this year’s Ten Best Bikes balloting.

But for all its attributes, the Seca II isn’t perfect. Fortunately, amending its shortcomings is relatively easy and, for the most part, inexpensive.

Upgrading the suspension was the first step. Though very compliant for around-town riding, the 38mm conventional fork and cantilevered single shock are too softly sprung and too lightly damped for backroad blasting.

For an affordable solution, we took the bike to Progressive Suspension in Hesperia, California. Progressive modified the fork’s damper rods, set the oil level at 6 inches from the top of the fork tubes (measured with the fork collapsed and the springs removed; stock is 4.4 inches) using Silkolene 10-weight fork oil, and fitted a pair of the company’s FZR600 replacement springs. Compared to the stock setup, the fork was significantly firmer, but still rebounded too quickly.

Replacing the 10-weight oil with the same amount of 15/20-weight Bel-Ray made a noticeable improvement.

Preloading the springs with

ln/i6-inch lengths of PVC pipe resLilted in the proper 1 inch of sack.

Progressive also fitted one of its Adaptive Shocks to our project Seca. The fully adjustable damper costs about $100 less than most other aftermarket shocks and is available for a limited number of single-shock Japanese sportbikes. For additional ground clearance and quickened steering response, our prototype Seca II shock was .2-inch longer than stock. After setting the sack at 1 'A inches, we settled on the third rebound setting (out of five) and left compression one turn out from full soft.

Next, we turned our attention to the Seca’s brakes. Although the single caliper and 12.6-inch front rotor work fine in most street situations, repeated stops from high speeds will cause the brake to overheat and fade. We pitched the stock rubber hoses and pads in favor of Galfer lines (complete with anodized aluminum fittings and protective spiral wrap) and asbestos-free Kevlar pads. A pint of AP Lockheed 5500 brake fluid and careful bleeding completed the upgrade. The result is a firm feel at the lever and plenty of fade-free stopping power.

We planned on roadracing the 600 in Yamaha’s Seca II Challenge series (see accompanying sidebar), so we left the engine stock, with the exception of replacing the 4-into-2 exhaust system and rejetting the 26mm Mikuni carburetors. Vance & Hines’ nickel-plated 4-into-l SS2-R is claimed to be one of the quietest aftermarket systems available and weighs 13 pounds, 11 less than stock. V&H’s latest silencer-a polished aluminum oval with triple-chamber

QuiTech baffle, high-density fiberglass packing and billet aluminum end cap-was also included.

The headers and corresponding Ssection bolted-on without incident, but the silencer fit so loosely that it leaked, even with the supplied springs and mounting bracket properly affixed. According to Vance & Hines, our pipe was an early production unit and the problem has since been solved.

The Dynojet Stage 1 jet kit (also available from Vance & Hines) consists of two sets of main jets, adjustable needles, drill bits, instructions and a troubleshooting guide. To install the kit, the fuel tank and airbox must be removed and the carburetors

loosened from their intake runners. Following the instructions for the Stage 1 kit (designed for use with mildly tuned machines using the stock airbox, with stock or aftermarket filter and/or an aftermarket exhaust system), we yanked the stock needles and slides, and enlarged the slide lift holes with one of the included bits and our power drill.

Next, we installed the Dynojet needles (placing the supplied E-clips on the recommended third groove) and the larger (#102) of the two main-jet sizes included in the kit. The final step was to drill and remove the EPA-mandated brass plugs covering the fuel-mixture screws. With the plugs removed, we turned each screw clockwise until fully seated, then backed it out two-and-a-half turns. Upon start-up, the engine idled and ran smoothly, but a trip to the dyno at Houseworth Power Services in Santa Ana, California, (714/554-1486) revealed that the carburetion was too rich. With the smaller #98 main jets, the engine produced 50.5 peak horsepower at 8900 rpm, a gain of only 1 horsepower over stock. With either of the supplied main jets, low-end and midrange were adversely effected. From 5000 to 8000 rpm, the Vance & Hines pipe was down as much as 4 horsepower to stock. Torque

also dropped off; from 4600 to 7800 rpm, the Vance & Hines pipe lost 3.5 foot-pounds of torque. We took the bike to a local Yamaha dealer for a leak-down test and found the engine to be well within Yamaha specs. In response, Vance & Hines says it is working on another version of the pipe that it believes will offer improved performance.

For a little pizzazz, we took the Seca’s three-spoke wheels to Sihilling Polishing, also in Santa Ana. The result was a dramatic aesthetic improvement that gets plenty of attention. On the downside, the wheels require a lot of elbow grease to maintain their shiny appearance. Once the wheels were polished, we spooned on a set of Metzeler’s

Comp K MEI s, in 120/70-17 and 140/70-18 sizes. We’ve used these tires in the past, and found them to be both sticky and relatively long-lasting.

Another old favorite is the project Seca’s chromed, Superbike-style K&N handlebar. Lower and slightly wider than stock, the tubular bar gives a more aggressive riding position. At full right lock, though, the Yamaha’s master cylinder now lightly contacts the windscreen. Fortunately, this is only a problem during tight, parkinglot maneuvers.

As anticipated, our Seca II project bike is a real backroad delight. The suspension took a while to fully dialin, especially the front end, but it is far superior to stock, and still compliant

enough for daily commuting. The $450 Vance & Hines exhaust is much louder than we had hoped, especially at full song. Short-shifting around town helps to keep the noise levels at a socially acceptable level, but given the performance loss we can’t recommend this system for the Seca II. Everything considered, though, our project bike is a winner. And a relatively affordable one at that; our street-going additions totaled $1828, and this could be trimmed substantially if you concentrated on suspension mods and left the detail and cosmetic alterations for later.

Now, if Yamaha would just give the Seca II an additional 150cc, we’d really be in business. □