Cycle News - Archive Issues - 1980's

--Yamaha Seca 550-- i ~ . 750cc perforlTlance, 400cc lTIaneuverability, 5!50cc price tag By Pat Eagan Photos by Charles Morey, Brad Zimmerman and Eagan More than a decade ago, the three-cylinder 500cc Kawasaki Mach III came to these shores and established performance standards for the half-liter class. But those standards dealt only with acceleration and top speed. Such things as handling. rider comfort and motor tractability - much harder to measure-dian quarta·mile elapsed time and trap speed - were rated secondary in im· portance. At last. with the introduction of Yamaha's 1981 Seca 550. we are able to buy a bike in that size and weight class that provides the performance of the Mach III combined with the hand· ling of a twin and the comfort of a midsize toura. Realistically, the Seca 550 does come up short when compared in absolute terms to each of these types of motorcycles. but as a complete motorcycle it is superior. While the Mach III could accelerate through the quarter a couple of tenths quick.a and two to three mph fasta, it lacked civility in a big way. Antics that are acceptable on the rack track are not necessarily desireable on the street. Heaven help you if you grabbed too much throttle in first gear. More than one rider turned his triple into a giant mouse trap when only moments before he thought he had everything unde.r control. When it came on the powerband. it did so with toggle switch effect. And anyone with enough money could buy one; no experience necessary. The problem for the rider who wanted to go slow was that if the motor was below the powerband. there was no useable torque. Now the Seca: Because of the peculiar torque curve which flattens out between 4.000 and 6,500 rpm. you get two torque peaks. To get around town. you short-shift the motor up through the gears at around 3,000 rpm. If you're in a 30 m ph zone. shift into fifth gear; sixth for 35 mph and up. Forty mph in sixth is about 3.300 rpm and in the middle of the lower torque peak. In that situation. if you need to accelerate past a slower car. merely roll on a little throttle. perhaps a quarter. and you are past the car. There is no need to downshift because the motor is putting out nearly three·fourths of the maximum torque at that engine speed. If you want to accelerate as hard as the bike will go. however. you sbould stay above 6.500 rpm because that's when the second torque peak starts corning in. And when it comes on the boil. the Seca will carry you past anything in its class except possibly the Kawasalti GPz550. Excellent handling is the Seca 550's strong point. The bike responds to rider input more like a 400cc twin than a 550cc four. It's easy to see why when you compare the Seca's geometry and dimensions with a Honda Hawk. The first and most significant point is the fact that the Seca is only 30 pounds heavier! And the weight is more compact; the Seca's engine cases are actually ~ inch narrowa than those of the Hawk. This is mostly because the alternator is placed behind the cylinders instead of on the end of the crankshaft. That gives more ground clearance. but more important it makes for a more centralized mass. The tighta the cenlfi of mass. the less effort required to lean the bike into the turn. The advantage of the Yamaha design regarding placement of the alternator is that the Seca's motor can be lower in the chassis and still have a good ,ground clearance. The Seca motor is 16 inches wide while a Kawasaki GPz550 is 19 inches at the widest point of the cases. The lower the center of gravity the more stable and responsive the bike will be. Crankshaft centerlines for the Seca and the GPz550 are 15 inches and 15.5 inches respectively. Comparing the geometries of the Seca and the Hawk gives even more insight as to why the Seca handles so good. Both bikes have the same rake angle at 27'. but the Seca has a bit more trail: 4.3 inches compared with 3.9 inches for the Hawk. And the wheelbase of 55.3 inches for the Seca is only ~ inch 10nJter than the Hawk. The increased trail and wheelbase improves high speed stability but would tend to make the bike less reo sponsive. The Seca compensates again with a more forward bias of weight distribution - 47.6% compared to the Hawk's 45.5%. The larger the percentage of weight on the front wheel, the better the front end will stick and steer. One shortcoming in the handling is responsible for the plush ride experienced down SoCal's dreaded 1-5. Shock damping is simply too soft for hard charging down the twisties. At least with 3,000 miles on the odometer. Riding up and down my favorite canyon produced a wallowing and pogoing effect at the rear set up by the bumpy sections and an ess section which has an elevation change in the middle of it. However. through the smooth sections and on the interstate. the suspension compliance delievaed a very plush and comfortable ride. Only on the roughest section of I· 5 did my back ever complain. For the "Canyon Crazies" thae are several good aftermarket shocks available. Another area where the Seca com· pares well with the Hawk is the brake department. Because the brake loading (pounds per square inch of swept area) is actually less on the Seca, 4.7 Ib.lsq. in. to 5.4 Ib.lsq. in.. the Seca has the bralting power to pull the extra weight down to rest in about the same distance. The lever has a very mushy feel to it which is probably a combination of the small half-inch master cylinder piston. for increased leverage ratio against the friction pads, and brake hose flex. The brake pads have probably the highest percentage of copper material of any O.E.M. pads. According to reo presentatives of Yamaha Motor Corp., the purpose of such a high copper content (55%) is to provide safe and con· sistent braking in wet operation. F~r. tunately. your testa got the opporturuty to test the brakes in this condition. With the rain pouring down. the front brake would let out a loud howl coming to a stop but would give consistent. safe stops. The rear brake delivered controllable stopping with little tendency to lock the wheel. The Seca 550 is one of the new generation of "High Tech" Yamahas. One of the innovations employed in the Seca is the new Yamaha Induction Control System (YICS). Using passages cast into the barrel and head. the four intake- pons are interconnected. During the intake phase of each cylinder, the other three intake ports will be delivering intake charge to the one cylinder through the YICS passages. Because ofthe size and angle of the subports. the effect is to swirl the incoming fuel·air charge thereby promoting bet· ter atomization of the mixture. Yamaha claims improved fuel efficiency. This is quite possible as we averaged over 50 mpg during the test and were not trying to achieve high fixtures. just average' around·town driving habits with occasional gassing it up for fun. Obviously. better figures could be obtained by someone who is driving conservatively to get the good mileage. Another technical advance (pardon the pun) is the new breakerless magnetically triggered ignition system. The transistorized inductive ignition has no mechanical advance .. Instead, it has a little electronic box which controls ignition timing. Thus. no periodic maintenance will be required to keep the ignition system working at peak levels. Two electric gadgets to prevent you from coming to grief are the oil level light and the sidestand cut-out switch. It's easy for a rider to overlook periodic inspection of the oil levd but with a light that comes on when the level gets too low, unfortunate and expensive accidents can be avoided. Also. on a conventional bike without this feature it would be possible to pop a seal or some similar oil loss situation whereby the rider might not be aware that he is losing lubricant with disastrous results. If you've ever heard of anyone leaving a stop with the sidestand down and then making a left tum at speed. you'lI appreciate the benefits of the sidestand cut-out switch. With the stand down. the motor can't be started; if the motor's running. when you shift into gear. the motor will die. A great step forward has bee.n made by Yamaha to save money for the new bike purchaser when it comes to wear and tear. A tum signal and its stalk is something that anyone can damage in a parking lot. Many a bike has slipped off its stand and fallen over onto its tum signals causing $15-30 worth of damage. The penalties of such an in· cident are great minimized by the new rubba tum signalstallts. Prior to our possession of this Seca. a rider had dropped the bike at slow speed on the left side scratching up a few things. The signal body itself was slightly scratched but didn't need to be replaced. Another thing about the tum signals is that they are the most convenient signals to use. Because they're selfcancelling. your thumb only does half the duty that a regular system requires. But also, if you want to cancel them, all that's required is that you push in on the button. No more trying to centa the switch while in the middle of an in· tersection with several cars aiming at you. With the current EPA requirements for emissions. many new bikes are jetted lean and need time to wann up on a cold morning. Not so with the Seca. At temperatures down to sub-40. the pro· cedure is to put your gloves and helmet on and do all the things you have to do before departing. When everything is set to go, hop on board. push the handlebar mounted choke lever forward. start the bike and take off. At these temperatures, absolutely no warm up time is necessary. The only problem with all of this is that sometimes you might forget to tum off the choke. That day you'll end with poor gas mileage. Yamaha styled and engineered the Seca as a sport bike. The cafe racer fairing and swoopy lines of the gas tank and tail section suggest movement. Responsive steering. excellent acceleration and top speed, superior cornering clearance, and good brakes provide the rider with an excellent too) for carvirig comers. John Glover, 1980 AFM number one. has raced his Seca three times now. and has yet to lose in the 600cc Box Stock class. John has provided us with adequate proof of the competitiveness of the Seca 550. Only a small percentage of Seca buyers will ever race their bikes. Most will be satisfied with the way the bike performs around town, on the free· way. and on t~ occasional c~g road. The Seca 550 provides 750cc performance combined with 400cc maneuverability and economy. And all that at a 550cc price tag. Most people will be happy with their purchase of the new Seca 550. • E 00 C') -------Secaspecs------Model XJ660RH Suggested list price ',' .: $~ Engine Four cylinder, four-stro e Displecement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 528cc Bore x stroke , . 67.0 x 61.8mm Compression ratio 9.6:1 Carburetor 14) Mikuni BS28 Ignition Transistor-controlled Lubrication , , . . . . . . . . . . . . . . . . . .. Wet sump Oil capacity : ' 3.1 qt. Transmission , SIX-Speed Overall length 81.1 In. Seat height. . . . . . . . . . . . . . . . . . . . . . . . . •. . . . . . . . . . . . . . . . . . . .. 30.9 !n. Wheelbase , 56.3 In. Dry weight , 401 lb. Fuel tank capacity 42 gal. 15

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