Yamaha YZ144
Price: $5599 + $819 + $348
Claimed Weight (no gas): 208 lb
Seat Height: 39.3 in.
Fuel Capacity: 2.1 gal.
This 144 was an experiment in seeing if we could build the ultimate small-bore two-stroke and it took a lot of tuning, as we expected. For sure the KTM 150 is the easier path by having someone do the tuning for you, but here is our setup for the YZ144 (since we did it for you also). Along with the Athena kit, we found that is it pretty important to change the stock pipe and muffler for the best power spread. We had our best luck with a FMF Fatty pipe and PowerCore muffler. We also found ourselves working between stock jetting and up to two sizes larger on the main jet depending on the temperature and the altitude.
With this setup the torque from the bottom to the top is boosted and the pull in the midrange is enhanced. Not near the top-end power level of the KTM 150, but it definitely beats it out in the bottom and the torque feel all the way through. This Yamaha was way more of a novice-friendly bike. It makes pulling out of the turns easier and keeping the dreaded bog at bay that much simpler. You end up using a lot less clutch, but the throttle response just wasn't as crisp or sharp as the YZ125's. (We did not have the chance to try some different reed valve systems which often fix this.) One of the best things about the 144 was that there was little, if any, difference in feel between the YZ125 and YZ144 in weight feel or handling. But in out-and-out racing with higher-skilled riders, there also wasn't much difference in the speed of the bikes, unless there were steep hills where the 144 would show its power advantage. For off-road or trail riding this is also a very potent package as the improved torque is very beneficial.
Yamaha YZ125
Price: $5799
Claimed Weight (no gas): 208 lb
Seat Height: 39.3 in.
Fuel Capacity: 2.1 gal.
Yamaha has kept the YZ125 alive with the most minor of updates for 2009, but that doesn't mean it is falling behind. That new front tire goes a long way! With very consistent handling and a suspension package set up perfect for 160-pound riders, the Yamaha is also adaptable to larger and smaller pilots. Our smaller guys found the Yamaha just a little bit less stable on the straights, but they were more comfortable in the turns. Since the YZ feels a little more planted than the KTMs and its handling just a bit more relaxed, they could get away with being less precise-something that riders who aren't that strong or are coming off an 85 can appreciate. The clickers on the YZ go a long way in tuning the ride, and with a little time almost everyone who rode the bike could get it to work. Riders 20 pounds on either side of 160 could get an even bigger boost by fitting stiffer or lighter springs.
As for the motor, the Yamaha has a very potent and an incredibly snappy power delivery. It comes alive at a very low rpm and it has a pretty good punch fairly early in the power spread. Then it will snap to life at any rpm with a big crack of the throttle, provided you are in the right gear. Like any 125, if you are a gear high coming out of a turn, you are going to bog and all the clutching in the world isn't going to bring it back alive. The YZ has a really good pull that is broad in the middle and it tells you when it is time to shift with enough cushion on the top-end overrev. It doesn't like to pull as long and hard on top as the KTM 125, but the KTM 125 is not this robust in the middle.