Long Term With The 2021 Yamaha YZ 125X

Written By: Dr. Gardner Tarlow

Can the YZ 125X really serve as a multipurpose moto-enduro bike?

If you have read my previous article on the 2021 YZ 125x you know that Kris gave the average Joe rider (me) the opportunity to test the bike. Well luckily for me Kris asked me to continue to ride the bike and give him my extended impression.

I’ve had the opportunity to continue to ride the bike for a few months now. I had been thinking of adding a 125 MX machine to my stable of bikes for mid-week moto for a while, however seeing how I mainly rode enduro, I was hesitant to have a track bike that sat in my garage. When Yamaha first debuted the YZ 125X, I was excited and wanted to see how well the bike could handle the work load as a multipurpose bike. As luck would have it, Kris offered me the opportunity to test the 2021 YZ1 25X and I jumped at the chance. I instantly fell in love with this small-bore bike for both enduro and motocross and I have once again been bitten by the motocross bug. 

I intentionally left the bike completely stock to hopefully get a better sense of the pros and cons as well as the reliability of this bike. This bike currently has 45 hours on it, approximately 20 hours on the trails and 25 hours at the track. I have only performed regular maintenance and played with suspension sag and clicker adjustments. The bike has continued to perform well and has been reliable on both the track and trail.

Not owning a newer 125 for the track to have as a yard stick, I felt this bike more than handled our local tracks and really didn’t give up much in track performance compared to a pure track bike. Recently however, I had the opportunity to ride back-to-back the YZ 125X and a stock 21 Husqvarna TC125. This was a bit of an eye opener for me as it took a bit of shine off the YZ 125X. I continued to prefer the YZs handling and rough track prowess, but the power difference pulling out of corners, down longer straights, and large hills was too much to turn a blind eye to. It would be interesting to ride the 125X back to back with the YZ125 to feel the difference.

In reality, I don’t know how important it is to compare the YZ 125X to a motocross track specific bike as that is not the designed purpose. In the same vein, I think it would be difficult to take a track specific 125 out into the hills, ride a rocky single track, with technical hill climbs/rock gardens for 2-3 hours and not feel completely beat up by the end of the ride. Each bike design serves a different purpose, especially when comparing the extremes of each riding discipline. The YZ 125X is designed to be a GNCC race bike, this means extended cross country, off road courses, and lasting 2-3 hours of racing. These courses will have sections which are tighter and potentially more technical than any motocross track and other sections that will be just as wide open as any motocross track or even short desert sections. Maybe the better question is which 125 can merge to perform all the different disciplines if you’re looking for a single 125 multipurpose bike. 

When straight up comparing the YZ 125X wet weight to the other 125 motocross bikes the difference is between 2-10 lbs difference. The YZ 125X is still very light, flickable, easy to muscle around, and place into whatever line you want. Unfortunately, shedding weight on a bike can get expensive and when you consider the HP to weight difference, this may be slightly problematic at the track if you are competitively racing. For me however this isn’t a huge issue as I am looking to have fun on days off.

The power of the YZ 125X engine is smooth, very controllable and builds from off the bottom all the way up to its top end. The bottom end lugability allows the bike to perform very well on slow technical climbs as well as allow me to change lines when trying to maneuver over slow rocky obstacles. The delivery of the bottom end also allows you to roll on the throttle at very low speeds without having to abuse the clutch too much which is nice for an old doc like me. This also translates well for motocross allowing you to be more creative with inside lines and also makes up for some riding technique deficiencies. The mid-range is strong and more than capable with both riding disciplines and it hauls my 185 pound frame around well.. The top end of the YZ 125X seems to rev out sooner than I would like and fall off, leaving you wanting a little more top end. In stock form this is where the YZ 125X suffers the most compared to a track specific 125. 

Modifying a YZ 125X to gain 6hp or more is possible, but at what cost to reliability as well as dollars. I don’t think I would mind pushing my YZ 125X back to the pits from the tracks edge, but it would make for a bad day of riding if you have to tow your bike back 2-3 miles away from your truck. 

Although not a hydraulic clutch, I was pleasantly surprised at how well the stock clutch performed despite the abuse of both enduro and moto riding. The clutch had a light pull and continued to perform with minimal adjusting even on my most abusing days. Being at 45 hours the clutch held up well and although it will get a new clutch, I believe there are a few more good rides on the existing one. 

The suspension on the 125X is essentially the same KYB setup as the YZ125 but with different valving, because of this, the YZ 125X has the potential to be as good as any YZ125. In its stock form it’s very ridable for the smaller rider, but at 185 pounds once you start getting aggressive or the track gets rougher, you notice the big hits in your wrists and feel the suspension moving thru the stroke too quickly. This unfortunately is going to be the case for all heavier  riders, so re-valving the suspension front and rear with a stiffer spring rate is par for the course with any 125. In stock setting the suspension is just too soft for motocross unless you are the intended audience (<160lb) and even then, it is too soft for a faster rider when considering motocross. Out on the enduro trail and tight single track the suspension valving seems very appropriate soaking up rocky uneven surfaces, but again would need heavier springs for the larger riders.

Being more of an enduro guy and riding primarily a KTM 300XC, I felt the YZ 125X was a blast in the hills, single track and small rock gardens. Although the 125 is much easier to throw around and significantly lighter weight than my 300, you have to ride a 125 with much more aggression to get through certain types of sections. The same way it is a blast to attack at the track you need to do the same out in the hills. I definitely felt like I could manhandle and ride the more difficult sections better on the 125 but by the end of the 3 hour rides, this constant need to attack the trail left me feeling more fatigued compared to my larger bore bike. I will say I think the YZ 125X would be a great tool for any rider to improve and work on extreme enduro style techniques.

My wish list for this YZ 125X would be a gradual build up. I typically replace parts as they need servicing or I damage them. At 185 pounds without gear and 45 hours of ride time, the suspension needs servicing. I would service as well as address changing the spring rate and more aggressive valving to better handle weekday moto. I find it easier to soften suspension with clickers for enduro than stiffen suspension for moto. I occasionally drop or dare I say throw my bike out on the trail when in trouble, so bike armor for off-road is a must. At minimum the bike needs an aluminum rear disk guard, plastic front disc guard, skid plate, linkage guard, radiator guards and hand guards. The difference between a good running 125 and the same 125 finely tuned, can be significant. The carburetor performance in stock form seemed adequate, but I feel there is some performance gain to be had with a reed valve system. I wouldn’t mind adding a high compression head, pipe/silencer combo to even the playing field at the track. This would help overall power and hopefully provide a bit more top end without sacrificing too much bottom end performance. The front brake performance is average and although appropriate for both disciplines, an oversize front rotor and steel brake cable would be an improvement. The YZ 125X gas tank is the same as the YZ 125 at 2.1 gallons and although it has a reserve petcock, it doesn’t extend ride time or mileage. I spent most enduro rides carrying gas filled water bottles in my fanny pack so a larger tank would be optimal. Unfortunately, most available larger tanks (3.2 gallons) seem rather large for track purpose. Yamaha should have designed and provided a slightly larger 2.5 gallon tank (similar to the WR450F),which would have been perfect and still small enough for moto. 

Without a doubt the YZ 125X can serve as a multipurpose 125. The more I rode this bike week to week, the more I appreciated what the YZ 125X could do out on the trail and at the track. Outside of competitive motocross, I believe the YZ 125X is a great alternative for someone wanting a 125 that can do it all with the least amount of difficulty going from one discipline to another.  

2021 Yamaha YZ125X Review From A Doctor's Point Of View

Dr. Gardner Tarlow has been my doctor for may years. Dr. T has helped riders like Tim Ferry, Ricky Carmichael, Travis Preston, among others over the years. Dr Tarlow also loves to ride and just like you and I finds his spare time at either the track or trails of Southern California. He has been bugging me to ride the YZ125 X since it came out last year so I thought it would be a good read to hear what an average Joe rider like Dr. Tarlow thought of the YZ125X. Here are his words. -KK

The YZ 125X was designed to be a closed course GNCC style race bike. It’s hard to imagine that a YZ125 with more bottom end, softer suspension, feather light and an 18” rear tire wouldn’t make a good GNCC race bike. Unfortunately, I don’t live on the east coast and my version of cross country is the high desert all the way to the foothills of the California mountain ranges. This means everything from sandy, rutted, rocky, hard soil with technical long hill climbs.

I was lucky when Kris gave me the opportunity to ride the 2021 YZ125X. To be honest, I had been bugging him to ride this bike since it came out in 2020. So naturally, it took me by surprise when he offered to let me ride the 2021 bike and write up a review.. Kris has a lot of options when it comes to having people test bikes and I didn’t imagine I would even make the list. I would consider myself an open novice for both motocross and enduro. I am not the target market for this bike. I already have my AARP old man card and at 5’10” and 190lbs without riding gear. It’s safe to say, I definitely put this 125s ability to perform well in the hills at a disadvantage.

My first few rides were at Glen Helen Thursday practice, followed by multiple days at Cahuilla Creek. At 190lbs I’m not the ideal rider for any stock 125 motor or suspension. Most important for me was to assess the performance of the motor. I’ve rode a few different 125s and I was curious to see how the motor would differ. Out of the box, the jetting on the bike seemed appropriate and pulled cleanly in almost all riding situations. Under heavy downhill braking, the motor seemed a tad rich and hesitated with a slight bog. Turning the idle up and resetting the air screw cleaned this up somewhat but most likely the bike needed a change of needle height. The motor had a good bottom end with strong mid and top end performance. The top end power and pull seems to flatten out more than a regular YZ125 but then again, each bike is designed for different purposes. Although the top end isn’t the same as most track 125s, it pulls plenty well for track practice days or club racing. When I found myself in the wrong gear, a quick fan of the clutch and the motor lit right up, minimizing my poor riding technique. I gladly would give up the top end performance for the enhanced bottom end grunt, if that term can be used for a 125. I had forgotten how busy you need to be to keep a 125 on the pipe. The suspension in general was not designed for my size, however I was able to dial it in to where I could ride it without major issues. I eventually settled on Fork compression 10, rebound 7, forks 7mm up in clamps. Shock at 103-104mm race sag (free sag 20mm, need stiffer spring) low speed compression 10, high speed compression 2 and rebound 8. Despite the bike being significantly under sprung for me, the bike didn’t have any harsh landings or do anything to spook me or make me feel like I needed to back it down. Once I got the suspension dialed in, I was able to take any line I chose and the bike had that classic 125 feel and sense of just falling over into turns and railing ruts. For a bike that I was hoping could serve dual purposes, this little 125x was a blast at the track. With the exception of having a kickstand stare at me each time I came back to the pits, I would’ve thought I was riding any stock 125 that had a really good, broad powerband.

I initially went to the track because I always think it’s easier to dial in a bike at the track versus out in the hills. I knew from a chassis and suspension perspective this 125x was going to be a blast on tight, undulating, rocky single track. The suspension being a bit under sprung was somewhat of a benefit and less of an issue for the slower speeds and rocky terrain. I actually liked that when I sat on the back of the seat the bike would squat a bit more and allow me to touch the ground, making it easier to pivot the bike more so than my properly sprung KTM 300XC. My bigger concern was that, despite being impressed with how well the 125x pulled up the hills at Glen Helen, could it pull the long hills we ride out in the high desert? Rolling off the throttle or chopping the throttle on a big hill climb is hard enough to recover from on a 300 but on a 125? I figured it would make for a long day of failed climbs. To my surprise, the 125x climbed extremely well. I think because you have to charge up climbs knowing you have to remain in the throttle forces you into more aggressive riding and this got me looking further ahead. That old adage of keeping the throttle on and using the clutch to regulate the power has never been truer than on a 125. I intentionally put the bike in unfavorable situations on numerous long climbs and to my surprise, was able to recover quite easily. There were some technical climbs that had changes of directions and I didn’t seem to dig holes with the 125x the way my bigger bore bikes sometimes do. The more I rode this bike in the hills, the more I actually enjoyed the challenge of climbing on a 125x. In rocky technical sections I felt like I could put the bike wherever I wanted and was able to rock, clutch and pop the bike through difficult sections that I might otherwise struggle in.

One of my last rides I ended up getting lost for an hour on an extremely tight, single tire width, rutted old single-track trail off property in San Diego county. This trail was literally non-stop rutted turning with little to no straights for an hour. The 125x was finally in its true playground and it was without a doubt the weapon of choice. The ability to muscle it around, diving in and out of tight rutted corners, ducking bushes, trees and dry ruts, able to lug 2n​d​ gear and still have the ability to pull out of sections with or without the clutch made me feel like I had a distinct advantage over my buddies on their bigger displacement bikes.

As much as I liked the track days, I enjoyed this 125x out in the hills even more. When it came to undulating, rolling, tight single track, I started thinking, “I need to buy one of these for my bike quiver”. There may be better bikes for both enduro and moto specific riding, but unless you’re planning on racing a 125 or simply can’t fathom having a bike with a kickstand, the YZ125X can absolutely serve as a dual-purpose track and very capable enduro bike. Now the only question is two-stroke versus four-stroke... but we all know the answer to that. -Dr. Tarlow

2020 Yamaha YZ125X/250FX Introduction

Editors Note: It’s hard to be in two places at once. Yamaha scheduled their 2020 YZ125X/250FX introduction in South Carolina after I booked a testing trip to New Mexico. With that being said, it’s not as easy as you think to find good people to help you give some quality feedback in this industry. I get countless emails/calls about wanting to help me with testing, but after I tell them to write me something on their own bike (as a test), send it in to me, so I can see if they can write, it usually ends in crickets. Most people just want to do the fun shit and go home, but there is more to testing than just riding the bikes. Colton Aeck and Dallas Dunn are two of only a few that I have within Keefer Inc. that I trust to go to an event like this. Colton is a quiet kid, but respectful and does what he says. He’s a privateer Supercross racer that doesn’t get to ride much off-road, so I thought the YZ125X/250FX machines would be the perfect fit (for him) to give you the reader, a perspective from an off-road newbie. Dallas is a single father that works as a heavy equipment operator that loves everything two wheels. He is your average blue collar dude that just loves to ride dirt bikes and is a bad ass at shooting photography as well as riding a BMX bike. I knew he would be a great photographer to bring this trip to life. Below is Colton’s story of how the event was, as well as his first impressions of how the bikes performed out in a true off-road setting. -KK

Written By: Colton Aeck

Photos By: Dallas Dunn

For 2020 Yamaha completed their line of "X" off-road bikes by introducing the new YZ125X. They also made major changes to their YZ250FX model by updating it with all the changes we saw from the 2019 YZ250F motocrosser. This past week, Dallas Dunn and I were invited to the home and training compound of off-road legend and 7 time AMA National Enduro Champion, Randy Hawkins to test out the new bikes. 

When I first got the call from Keefer a few weeks back, I was pretty excited, but also a bit nervous. In the past few years I've spent the majority of my time riding and racing Supercross. Besides a few WORCS races back in 2012 as a B rider, I've had zero off-road experience. By saying that most of you probably know, off-road in the wet coast desert is almost the complete opposite of what you'd find in the tight woods at a GNCC or enduro on the east coast. As we pulled up to Randy's on Tuesday we arrived at a big open pasture that was surrounded on all sides by hills and woods. It was a brisk 28 degrees and I thought to myself this west coast boy is going to be coming out of his shell this week!

Randy and the crew from Yamaha set up 3 separate courses through the woods, each with a variety of what you might expect to see at a GNCC or National Enduro. We had a variety of open fire roads, ultra tight woods, single and double track jeep trails, steep uphills/downhills, creek crossings, and there was even a grass track as well as a motocross section. Other than some frozen fingers in the morning and having a run in with more than a few trees along the way, I can honestly say that it was some of the most fun I've ever had on a motorcycle. Throughout my life I've never understood why people would choose to ride or race off-road. Moto and Supercross just always seemed a lot better for me. Not to mention ripping across the desert wide open and eating a bunch of dust, just doesn't sound like much fun. Well, riding in the woods is a completely different animal, but riding these Yamahas in the woods of South Carolina has really changed my mind about off-road riding in general. In fact, it has my gears turning and thinking more about what I'd like to do after my moto career is over. 

I strongly encourage all you moto guys out there, if you've never been trail riding out in the woods, find a place, find a bike, and go try it! Racing is my passion, but just like anything, if you do it enough it can turn into a job as well as burn you out on something that you love. This week I had the chance to get back to my roots and really remember why I love dirt bikes so much. Being out in the wilderness, with just yourself, your bike and a couple buddies really reminds you why you got started riding in the first place. It's been a long time since I've gone riding all day long and still wanted to keep going. The Yamaha crew just about had to pry me off their bikes each day just so they could prepare for the next day of riding. 

Enough about me and how much fun I had, you guys are here for the testing, so let’s get to it. Yamaha's goal with their "X" line is to have a purpose built bike that's ready to ride and race in off-road situations. They took their motocross bikes and made a handful of changes to each to better suit off-road riding. 

The YZ125X shares most of its parts with the YZ125, with a few key changes, the biggest being engine and suspension. The X model has a different cylinder head shape, different powervalve shape/settings and a new ECU setting to match the engine changes. The suspension components, as well as spring rates remain the same, the only suspension change is in the valving. The YZ125X also comes with a kickstand, o-ring chain, reserve fuel petcock, 18 inch rear wheel and Dunlop AT81 tires. 

The goal was to make the YZ125X more capable for off-road and after the crap out of it, I think they did just that. The engine changes lead to a broader, easier to ride engine character for the tight, slippery terrain I was testing in. The engine hits sooner in the RPM range (although not quite as hard as a YZ125) and pulls longer on top. The engine is really what you'd expect from a 125. It's not a rocket ship, but it is a lot of fun to ride when riding in that sweet spot. I was really impressed at how well it climbed some of the steep hills on Randy's trails. In situations where a 250F or 450 would break traction and start digging a hole, the 125 would stay light and on top of the dirt, driving with forward bite.

To my surprise the suspension worked really well for me on initial plushness and small impacts, but left me wanting more hold up as well as bottoming resistance on hard impacts (like creek crossings, or big G outs). Anything more than a medium size impact left me with an empty/soft feeling front and rear. I was able to get the fork and shock to bottom fairly easily when I started to feel comfortable and push it. Honestly though, soft suspension was what I expected from an off-road type of machine, but I am so used to such stiff settings on my SX bike that anything feels soft to me. I don't think a 180 pound Supercross pro is the target market for the YZ125X, but I enjoyed it a lot. Your typical younger generation off-road kid or even the older more mellow weekend warrior will have a blast on it while feeling like a hero through the trees, but may want a little stiffer suspension set up once broken in. I think this bike is the perfect tool for the younger generation moving up off minis or a newer, less experienced rider just starting out in off-road. The YZ125X is not intimidating to ride and is light enough that almost anyone is able to pick it up after a spill.

The bike I enjoyed the most was the YZ250FX. The 2020 YZ250FX received all the changes we saw to its moto brother, the YZ250F in 2019. This means a completely new chassis and engine, plus all the off-road goodies you'd expect the X to have. The X differs from the standard YZ250F, with stiffer front engine mounts, (designed for off-road), GNCC specific suspension settings, a kickstand, 18 inch rear wheel, O-ring chain, skid plate, a check engine/low fuel light/sensors, oversized gas tank, and the big one, a wide ratio six-speed transmission. Also new for 2020 the X now utilizes the Yamaha Power Tuner app so now you can wirelessly adjust your fuel and ignition mapping all from your phone. Whether you're a beginner or a pro, chances are you can find a map that makes you happy out on the trail.

On the trails, the YZ250FX was insanely fun to ride, I really had a hard time finding anything to critique honestly. I've never ridden suspension that was setup specifically for off-road and I was really surprised how well it would soak up small rocks and roots. I have experienced trail rides before on stiffer suspension and would find myself deflecting off everything on the trail. With the YZ250FX I’d approach rocks and roots expecting my front wheel to grab and deflect, but the bike would roll right over them with ease. It also had good hold up as well as bottoming resistance when riding over big logs or on hard impacts/landings. If I had to nitpick I would want a little more damping feeling through the mid-stroke just so I could start to push more when feeling comfortable. I know I would want to go faster, so I need to forecast my suspension settings accordingly.

 The YZ250F has been a class leader in the engine department for a few years now. I am not a 250F guy, but when I have tried the YZ250F in the past it blew my mind with how much torque it had. The X uses the same engine, so the torque feeling is just like how I remember it. It has a strong bottom end that pulls hard all the way through the RPM range. I enjoyed the wide ratio transmission and I found myself riding almost everything in 3rd gear, only using 2nd for really tight sections and occasionally on a steep hill climb. I can't really imagine a place where 1st gear would be very useful because after getting about 10 feet from the truck, I was out of first and never touched it again. The YZ250FX loves to lug and I have come to find out that lugability is important in the woods. The only major compliant I could come up with is that the YZ250FX is fairly difficult to start in gear. Unless you're in neutral, plan on it taking a few seconds to get the bike fired up or use the throttle a little bit in unison with the start button. Keefer is going to experiment with maps for you all and will post them up here on Keeferinctesting.com very soon. I will let him handle all of that stuff!  

Just for fun, I also had the chance to ride the YZ450FX on our last day at Randy’s. Being a 450 guy, I thought I would love it, but honestly the extra weight and power was just too much for me in the tight woods. This made me appreciate the YZ250FX even more because of its fun and easy to ride nature. The YZ250FX is really easy to just jump on and ride and when you start to push it, you don't get the feeling that you're one whiskey throttle away from a head on with a tree. I really think the YZ250FX is the better all around bike for this type of riding and anyone from beginner to pro could have a blast on it. 

Overall I was super impressed with Yamaha's additions to their "X" lineup. They are designed to be race ready for GNCC type riding and I think Yamaha did a great job. I know most of you Keefer Inc. readers are moto guys like me, but trust me when I say, “don't knock off-road until you try it”. Support your local riding spots and get out on the trails and ride. You'll probably be like me, re-kindling your love for dirt bikes and wondering why you didn't try it sooner! See you soon off-road! See you soon! -Colton Aeck