Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/126790
.... Q.) .D o .... u o The only changes to the YZ490 are the addition of a front disc brake and the Brake Actuating Suspension System. They're not water-cooled. " , .Ll"2.J [L:~ : . - -- - (Above) The diagram shows a cable connecting the rear brake pedal to the rear shock reservoir. (Below) New silencers have steel cores. (Top left) TakaS8go rims now have a solid bead.rea. (Top right) Front disc brakes have dual-piston single-action hydraulic calipers. (Below) The B.A.S.S. system makes braking over bumps smoother. A I CONVENTIONAL SETTING 4 II WITM BASS. porting, pipe, reed valve, powervalve mods, cylinder head mods and new ignition curve, the '85 YZ has gained enough top end to allow the use of a smaller carb to boost low-end and throttle response. The YZI25 also has new thinner frame tubing; and there's a new aluminum head stay running between the cylinder head and frame to reduce vibration. Last year the YZl25's radiator mounts bent and caused radiator cracking. The 1985 version ha's stronger mounts and extra brackets. On the track, the new 125 definitel y has more power; handling and suspension are still first rate. The . B.A.S.S. system seems to work very well. One of the most popular modifications mjlc;i~ b¥.priv~t~eI.st9J-beir IPM YZ250s is the installation of a longer, YZ490 connecting rod - Ricky Johnson's championship-winning YZ was modified that way, too. So we were surprised to find that the 1985 YZ250 doesn't have the longer rod. According to Yamaha spokesmen, engineers were worried about tarnishing the YZ250's reputation for reliability, and that they're still not certain if that modification causes durability problems. . Instead, the YZ250 gets slightly increased compression and a new piston with ribbing underneath the"dome to increase strength. There's also a lighter flywheel. The '85 YZ250 still has gobs of low end horsepower but top-end power has been increased. Throttle response is quick and clean, while it revs out v~ry qui~klYt. I ( I I) <' ( I 1 Suspension feels very similar to last year's YZ but is slightly stiffer, because of the use of heavier fork . springs and slight damping mods in the shock. When we£irstrodethe250, the front disc brake ,didn't feel very strong. It takes a few bours of riding to break the pads in before they start to grab; nonetheless, it still wasn't as strong as we expected. We were very disappointed to see that tbe YZ490 isn't water-cooled. Thefolks at Yamaba said they left off water-cooling to keep tbe cost of the bike down. It still will cost slightly more than the '84 YZ, but Yamaha says that the 490 will be much cheaper than the competition. The 490 has the B.A.S.S. system and the front disc brake; no engine performance mods were made. The seat is 15mm thicker over its ;en,ti;re length, th~ kiGkstan J shaft and stopper are now machined as a single unit for increased strength and - like all the YZs - the plastic side panels are 0.7mm thicker. The YZ490 is still a very powerful machine, and all of that power is found on top~ It doesn't have earthshattering low end, but it makes up for it [rom mid-range on up. However, vibration is a problem thrpughout the powerband. Because of the abrupt power change from low-end to mid-range and the vibration, the 490 is a handful to ride. Handling-wise, stability is the 490's strongpoinL Its suspension works very well and can keep up with the powerful motor on rough tracks. The forks are stiff because of heavier springs, and the brakes work slightly better than the 250's; both get better with age.. -- • Ie 131