Power And Suspension For the Tt600
POWER AND SUSPENSION FOR THE TT600
A LITTLE MONEY AND THE RIGHT PARTS TRANSFORM YAMAHA'S TT600 INTO A SWEET OFF-ROAD BIKE.
When we tested Yamaha's TT600 (September, 1983), we found much to like. The basic package had a strong, good-looking frame, nice engine, and reasonable handling as long as the bike was ridden slowly. Faster riders didn't like the soft suspension and wanted more power. Still, the bike was fun to ride and we de cided we'd keep it around. Yamaha might discover the too-soft suspension in time to beef-up the '84, making the suspension fix a simple retro-fit from the
dealer's parts book. Well, it didn't hap pen, the `84 TT600 got new decals and the same soft suspension. We started calling aftermarket firms.
Gil Vaillancourt, owner of Works Per formance, is a specialist at fixing suspen sion systems and he owns a new TT600. "Sure, I can make it work," he said. "Send the shock to me. I'll rework the inside and fit a new spring. The stock spring is a hundred pounds per inch (ppi) too soft. Send the fork dampers too, I've got a simple fix for them. The fork springs are also too soft. The stock fork
springs are 16 ppi, Yamaha's heavy-duty TT600 fork springs are 19 ppi, mine are 23 ppi." (Compressing a 23 ppi spring one inch requires 23 pounds of force. Each additional inch of compression re quires an additional 23 pounds of force.) `The Works Performance TT600 shock fix is extensive. The shock is disassem bled and the stock damping washers dis carded, the shock shaft is machined for 1/8 inch more travel for a half inch more travel at the rear wheel, and the piston separater in the shock reservoir is dis carded. New valving (spring-loaded balls placed over drilled holes of varying sizes) is installed in the shock body, and a Works bladder separator is used in the reservoir. The shock is then filled with Bel-Ray LT56 shock fluid, reassembled and pressurized with nitrogen. A progressive 350-430 ppi spring replaces the stock 250 ppi spring. Price for the complete job, including the spring, oil, valving and labor is $200. The fork damper modification consists of drilling the damper rod to soften mid-stroke action. This costs $15. The 23 ppi fork springs cost $38.
The TT600 engine is delightful stock but we could feel more power hidden inside, so White Bros. Cycle Specialties was the next firm we contacted. We didn’t want anything radical, just a bit more punch. White Bros, has four different exhaust systems available for the TT600: an add-on SuperTrapp silencer ($74.95), a complete SuperTrapp exhaust system including headpipes ($129.50), an unsilenced steel Baja racing megaphone ($29.95) and an aluminum megaphone that’s silenced ($69.95). The headpipes sell for $97.95. We ordered the headpipes and the aluminum megaphone ($167.90).
The stock air filter is too small, it clogs easily and looks fragile. White Bros, recommends replacing the stock filter with a K&N cloth filter ($26.64). Installing the K&N is easy, requiring only five minutes if you take your time. The airbox looks restrictive, so we drilled some holes in the side cover to ease air flow.
After reassembling the suspension parts (10 w fork oil, 6.0 inches from the top of the stanchion, spring removed, forks bottomed), we installed the White Bros, headpipes and aluminum megaphone. The exhaust system comes with easy-to-follow instructions and recommended carburetor jetting, (the jetting has to be richened on both carbs). The White Bros, pipe fit perfectly, nothing needed modification and best of all, the system is five pounds lighter than stock.
Maybe the best part of this story is that all of the replacement parts and modifications work well. The White Bros, pipe, K&N air filter and richer carburetor jetting give a significant horsepower boost, most of it in the midrange. Now the 600 feels like a 600. And the bike doesn’t burn more gas. With the engine making more power, the rider doesn’t have to use as much throttle.
More power with the stock suspension would be a waste. With the Works Performance suspension, a good rider can ride the TT600 at high speeds across rough ground and live to tell about it. The bike is still big and heavy but it’s now very controllable, less tiring and a bunch more fun. One of our guys entered the modified TT600 in the Barstow to Vegas Hare and Hound desert race and managed to win a trophy. The bike didn’t miss a beat.
If you own a new TT600 and are disappointed with the lack of suspension and power, give these guys a call.
Works Performance, 8730 Shirley Ave., Northridge, Calif. 91324. Phone (213) 701-1010.
White Bros. Cycle Specialties, 11750 Seaboard Circle, Stanton, Calif. 90680. Phone (714) 895-1991.
