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Comparison of the Yamaha YZ 125/2004 versus the YZ 125/2005

Slim, almost

Yamaha’s new 125cc crosser has slimmed down significantly. Is it also faster than its predecessor?

Somehow you had the feeling that the air was finally out of the cross two-stroke engines. Because nothing decisive has happened in the last few years. With the four-stroke colleagues, however, things really went off. Hosts of technicians rushed with tremendous zeal on the new steam hammers that revolutionized the cross world. More pressure, less weight, more dynamism every year.
But suddenly, like Kai, a whole series of new two-stroke engines are coming out of the box. Better, lighter ?? like that Yamaha YZ 125. It might be an exaggeration to speak of a renaissance, but the two-strokes are by no means defeated. It is astonishing that they apparently still have a lot of potential. After all, a motorcycle as exhausted as an eight-liter crosser seemed to be until now, can lose a whopping 3.3 kilograms in one fell swoop. However, this is only possible with a lot of consistency, as the little YZ proves. So with a new aluminum frame and a completely new engine that now has six instead of five gears.
MOTORRAD off-road expert Didi Lacher tested what this radical cure would bring on the slopes in a direct comparison of the Alu-YZ from 2005 against its predecessor model with the steel frame. So much in advance: The YZ has remained a typical Yamaha, but both-
the chassis as well as the drive are visible
make clear differences. Like its predecessor, the new engine is in the
Top performance not a high-flyer, but convinces with efficiency. And it is now even easier to drive because the usable speed range is wider. The 2005 engine kicks in earlier, then goes
completely linear through the speed range and also rotates properly at the top, while the strength of the predecessor is more in the middle range.
Shifting the new six-speed gearbox requires noticeably more power, at least in the case of the test machine, and idling is difficult to find. On the other hand, the aisles are secure when you get them in. The advantages of the six-speed transmission ?? narrower gradation with wider spread ?? are less important in practice.
In contrast to those from other manufacturers, the aluminum frame is not designed as a bridge frame, but is almost identical to the tubular guide of the conventional Yamaha steel frame. You actually expect that the difference between the two materials will not have such a strong impact. As a reminder: Honda initially had problems with the transition to the aluminum frame due to the excessive rigidity of the massive bridge frame. This is not the case with Yamaha, at least not as pronounced. Still, typical Pro-
problem of a light metal chassis. Namely the sensitivity in the chassis setting. While the old machine works fine even if the set-up is not optimal, the new chassis needs to be meticulously adjusted.
In particular, the negative spring travel at the rear should be chosen a little larger, as with the aluminum Hondas. At 25 millimeters, which is the right value for the steel frame, the 2005 YZ behaves rather stubbornly and unwillingly. It needs at least 30 millimeters, better still a touch more. On a narrow, hard route, it is also advisable to put the fork four millimeters deeper, this puts a little more pressure on the front section.
The new fork can really use that. Because it works pretty hard and insensitively in the middle range, but often hits through on landings. In order to prevent this, despite the hard basic set-up, a relatively high pressure level must be used. Otherwise, the suspension setting specified in the manual fits quite well. MOTORRAD worked out the following set-up on the narrow slope in Walldorf. Fork: compression 15 clicks open, rebound 9 clicks; Shock absorber: low-speed compression 11 clicks, high-speed compression 1.75 revolutions, rebound 12 clicks (all information based on the closed state).
The reduced weight is barely noticeable during normal driving. Because the predecessor is quite top-heavy, it can be easily directed in tight curves. The new one cannot do this any better, even with the optimal suspension setting. The pounds saved ?? measured 90.2 versus 93.5 kilograms ?? are especially noticeable when jumping. There is the 2005s-
YZ easier to direct and control. In terms of stability, the Yamahas have always been exemplary, the youngest is a tad better in a direct comparison on fast sandy stretches.
Because the tank and seat are unchanged, the ergonomics are retained. But the steel handlebar is finally a thing of the past, all new Yamahas have light Renthal aluminum handlebars. Another advance is the front brake line, which is laid directly upwards without a loop, which improves the pressure point and feedback.
All in all, a clear boost for the eight-liter two-stroke engine that brings it closer to the 250 four-stroke engine. Thanks to easier maintenance and repairs-
In any case, the two-stroke engines remain an interesting alternative.

Technical specifications

Engine: water-cooled single-cylinder two-stroke engine, flat slide carburetor, Ø 38 mm, membrane inlet, outlet control via electronically controlled roller, six-speed gearbox.
Bore x stroke 54 x 54.5 mm
Cubic capacity 124 cm³
Compression ratio 8.6 to 10.7: 1
Rated output 28.7 kW (39 hp) at 11500 rpm
Max. Torque 25.5 Nm at 10000 rpm

Chassis: double loop frame made of aluminum-
minium, upside-down fork, central spring strut with
Lever system, forehead disc brake, Ø 224 mm, double-piston floating caliper, rear disc brake, Ø 219 mm, single-piston floating caliper.
Tires 80 / 100-21; 100 / 90-19

Dimensions and weights: wheelbase 1443 mm, steering head angle 64.5 degrees, caster 104 mm, spring travel f / r 300/315 mm, seat height 994 mm, empty weight 86 kg, tank capacity 8 liters.

Warranty three months
Colors blue
Price including additional costs 6095 euros

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