Moving Up To A 125 Two-Stroke
A 125 two-stroke can be a great bike to have in your stable, especially when your little racer is outgrowing his or her 85. It also can be a great bike when you’re looking to put a little more fun back into your riding. We took our 2017 Yamaha YZ125 and 2017 KTM 125 SX testbikes out and let two growing 13-year-olds try their throttle hands out on each of them. For some extra fun we also put a couple of “stuck in their way” four-stroke vet riders on the machines to see what they thought of going back to their roots. And to cap it off we handed the bikes to a current pro racer who just earned his Supercross license this year.
The Yamaha has a barky, very crisp, reactive engine character that is extremely fun on low-end. Midrange is quite friendly (for a 125) for lugging riders, and with just a couple stabs of the clutch lever it is back up and screaming. Top-end pull is strong but signs off a little earlier than the KTM 125 SX. The suspension of the Yamaha is its strong suit. The KYB SSS fork is very plush, comfortable, and consistent over the course of a long moto. The rear end of the bike matches the front end; it is plush, moves in the stroke, and feels balanced even when the track gets rough. The chassis is light (of course, it is a 125) and is fairly easy to get into ruts and corners.
The 2017 KTM 125 SX doesn’t have the bottom-end hit the Yamaha does, but it makes up for that in mid to top-end. The over-rev of the orange screamer is impressive, and the carb is jetted very cleanly from the factory. The WP AER fork has great hold-up but not as much comfort in the mid-stroke as the KYB bump sticks have. The shock has that WP “dead feel” and doesn’t kick or react easily on decel bumps. The chassis does feel a little lighter than the Yamaha, and the orange bike gets through the middle of corners a little easier as well.
Having a 125cc two-stroke as your kid’s transition machine to the big bikes is very important. Why? Because 125 two-strokes are lighter and less intimidating than 250cc four-strokes can be. Chances are when it’s time to move up from an 85 the rider’s weight range will be between 100 to 130 pounds; with the amount of torque a 250 four-stroke puts out nowadays, that power-to-weight ratio might be too much for the little gal or guy to handle when they get tired. Also, a 125 two-stroke will help technique and help the young rider learn to ride with aggression, without having as big of a consequence as a four-stroke.
For example, when riding a 125 two-stroke, it is difficult to hit an inside rut and be able to clear a larger-size obstacle right out of the corner, so younger riders will learn to take the outside and carry more speed to clear the obstacle. With a 250 four-stroke, some young riders will get the sense of the bike having enough torque to be able to clear from the inside. This might lead to them making more mistakes coming out of the corner and not clearing an obstacle.
Another advantage is that some maintenance, like working on the top end, is much easier to do on a two-stroke. Spending time in the garage working on bikes together (when it is easier) can be a more pleasant experience for both parent and rider. Consider this: Your young child is learning and advancing at a rapid rate, and the love they will create for riding their dirt bike will be growing. They will be putting tons of hours on their machine, which means tons of wear and tear, and the cost and maintenance of a 125 will be easier on your wallet.
Sometimes stepping down to a 125 can awaken the fun factor for an older rider or maybe help them get reacquainted with how to ride more aggressively. If anything, four-stroke technology has taught riders to work less and ride faster. Four-strokes are so easy to ride and are so fast that technique and aggression can get lost along the way. It is always an eye-opening experience to any longtime four-stroke rider who gets on a 125 on how much fun, and work, it is to ride.
Riding a 125 feels like you’re riding a bicycle compared to four-strokes. And as much effort as it takes to ride fast, it takes less effort to get it into corners and lay it over (which makes you feel like a hero). Either one of these machines can help form a solid technique foundation with the younger crowd but can also reignite the lost flame that once burned in an older rider’s riding regimen.
The Yamaha YZ125 and KTM 125 SX are great platforms to build your riding skill, become more confident, and possibly rebuild some of your lost technique. There always seems to be a time and place for a 125 two-stroke in a rider’s two-wheeled career, and following are five opinions (two stepping up, two stepping down, and one current professional motocross rider) on why either of these bikes should be considered.
13 years old, 5’4”, 120 lb., Off-Road District 36 Youth Mini Champion
I usually ride and race a Super Mini Yamaha in the AA85 youth class, mostly off road. At first glance I thought the 125s looked a little tall and worried that I might not touch the ground. But once I climbed on I found I could stand fine. Trying to kickstart the KTM 125 was hard because of the compression compared to my mini, but as the day went on, it became easier to start and I was getting used to it. The clutch was very smooth with lots of room to slip before it grabbed. Unlike my supermini that I can hold wide open through the turns, I needed to constantly slip the clutch or remember to downshift, as the 125 would bog if I didn’t do this. Coming into turns, the brakes worked great. They didn’t lock up and send me skidding like on my mini.
The larger wheels and wheelbase smoothed out the braking bumps. The same bumps would feel like a whoop section on my mini. The suspension was great since I’ve been starting to bottom out on my mini when I come up short on a jump. Now we have to make it stiff to prevent that, but then it’s too stiff for the rest of the terrain. Having more travel to work with feels nice to have it set up for every aspect of the track and trail.
The seat gave me lots of room to move forward or back with ease, and I didn’t feel like I was stuck in a saddle. Having a bigger frame and bar that fit me better makes it easier to handle in a way that feels less sketchy. The little bike is starting to make me feel out of control at high speeds. On the 125, I felt really in control in mid-air as well as [through] high-speed sections and whoops. I could also hammer through rough sections or holes easier.
Overall, after riding the 125, it’s what I want to keep riding all day. It seems hard to go back to the Super Mini.
13 years old, 5’4”, 95 lb., Mini Sr. 2 12–15 Loretta Lynn’s Bound
I currently ride and race a YZ85 and had a blast trying out some 125s. I will be making the transition to the bigger bike soon, and today was my first time riding a 125 two-stroke.
The first thing I noticed was how difficult it is to get the bikes to lean over because of their increased size and weight, but after a few laps I became more comfortable and used to the bigger bikes. The suspension was another thing that was a negative—but also a positive. Both bikes seemed a little stiff coming into corners, which made it difficult to lean over. The bikes felt tall, which made me feel really far away from the ground. The suspension also leads us right into the positives. It was great for bigger sections like rhythms and massive jump landings. I definitely never bottomed these bikes like I often do on my 85.
The next thing I enjoyed was the power, especially the low-end power on the Yamaha. I felt more confident in the corners knowing the bike had the low-end power to pull me out of the rut. The KTM had slightly better power through mid to top, and with more speed like this you need proficient brakes. The KTM definitely does the job. I felt like as long as I had good grip I could slow it down comfortably.
With some great things about both bikes, I am certainly looking forward to making the jump to a 125 soon.
48 years old, 6’0”, 180 lb., Former ’90s Pro
I had National number 21 in 1991 and was a top privateer from the ’80s and ’90s. However, I have been out of the sport and off a dirt bike for about 15 years. But today I had a chance to relive and ride 125cc two-strokes that I once raced full time. The KTM 125 SX and Yamaha YZ125 that I rode were incredible. The brakes on bikes nowadays have so much more stopping power, and the engines also seem to have quite a bit more power but are more controllable as well. I thought I could jump on a new 450 four-stroke and start the riding process all over, but all I can say is, “Wow.” It had too much torque and power right out of the box.
If you’re a little bit older guy like myself, love to ride motocross, and are maybe a little intimidated by the big four-stroke thumpers, you could do yourself no wrong by getting yourself a 125. It has plenty of power, and manageable power at that, so you can flick them around and feel like you’re in the ’90s again. The suspension holds up yet is more plush than some four-strokes I tried for my older joints, which makes me want to try and ride longer motos. The 125cc bikes have really come a long way with the technology in the last 20 years and make me want to start riding again!
39 years old, 5’11”, 170 lb., Vet Pro
I get to ride 125 two-strokes once or twice a year being the test editor, but every time I seem to get off of them a couple of things spring into my head. One is that I really notice how lazy I get being on a 450cc four-stroke. Riding the Yamaha and KTM 125s makes me really work for every single obstacle on the track that I take for granted on my 450. Both bikes surprisingly will jump some sizable gaps but will force me to really perfect my positioning on the bike and line choice. I love this part of a 125. It makes me think a lot more on the track and work for every second I want to shave off of my lap time.
Second is how light and easy it is to put the bike where I want to. I can leave the throttle on all the way around sweeping corners, and it will stick all the way through. As hard as you have to work around the track, the lightweight feeling of both bikes does not correlate to a high heart rate for me, which means I don’t get as tired as quickly.
20 years old, 5’7”, 155 lb., Current Professional Supercross Racer
I am a professional motocross racer, and I just got my supercross license through the Road to Supercross. I ride a Honda CRF250R normally, but it was really an eye-opener to ride the YZ125 and KTM 125. I haven’t ridden a 125 in three years, since I rode Schoolboy 1.
It was a cool experience to jump back on the bikes after being on four-strokes for so long. I noticed that the 125s are a very good workout very quickly. The bikes teach you to keep up your momentum. If you can’t keep the bike in the right gear or in the power, you will not be going anywhere. The 125s keep you thinking while you are riding about the gear you’re in, the lines you take, and hitting your shifts at the right times. There is a lot going on while you are riding, but if you can control everything, it will help you that much more jumping onto a 250F or any other four-stroke.
The KTM 125 and YZ125 are great bikes for all types of riders and skill levels. The bikes are a lot of fun and keep you on your toes to keep the bike on the pipe, but they are so much fun to ride and it makes me want one again.