In my First Ride Review of the 2017 Kawasaki Z125 Pro I mentioned, “the Kawasaki, and its oversquare Single, feels like it has more bottom-end grunt compared to the Honda.” Of course, the Honda in question here is none other than the Grom.

Apparently, my butt dyno needs some calibration. We’ve finally got our hands on a Z125 Pro and the first place we took it to was an actual dyno – the one operated by our friend Chris Redpath of MotoGP Werks – and the result was a little surprising. The baby Z spun the drum to the tune of 8.3 hp at 7800 rpm, and 6.5 lb-ft at 6100 rpm. For comparison, in stock form the Grom puts out 8.7 hp at 6700 rpm and 7.8 lb-ft at 5200 rpm. So not only does the Honda make more power and torque than the Kawasaki, it also pulls off the feat with fewer revs. Advantage Honda. On paper, anyway.

Peak numbers are one thing, but the overall dyno curve is another. The Honda Grom wins on both accounts compared to the Kawasaki Z125 Pro, at least in stock form. The Z has a slight edge once the tach needle reaches the upper limits of its sweep, but that really only matters at the track.

Peak numbers are one thing, but the overall dyno curve is another. The Honda Grom wins on both accounts compared to the Kawasaki Z125 Pro, at least in stock form. The Z has a slight edge once the tach needle reaches the upper limits of its sweep, but that really only matters at the track.

So why was my butt dyno fooled? Gearing is a big factor. The Z125 is geared lower for each of its four gears compared to the Grom. Combining this and the Z’s revvy nature was enough to trick me. Not to mention, discerning between 0.4 hp and 1.3 lb-ft of torque without riding the two back-to-back isn’t easy.

Beyond the peak numbers, it’s clear on the dyno that the Honda shows an advantage throughout the fat part of the rev range, producing significantly more horses and torque (percentage-wise) than the Zed. It isn’t until the 7400 rpm range that the Green Machine ekes out a small advantage, but by this point an upshift should be looming in the horizon.

The Honda Grom has been a sales success, so it's natural for others to want a piece of that pie.

The Honda Grom has been a sales success, so it’s natural for others to want a piece of that pie.

The Kawasaki likes to rev, which could make it an attractive option for those who plan on taking it to the racetrack, as little bikes like this and the Grom are proving to be popular among mini-bike racing organizations across the country. Once the aftermarket starts finding ways to make the Kawi breathe easier, the baby Z should liven up in the upper revs, as we found with our Project Honda Grom.

Away from the racetrack, in stock trim the dyno numbers would point towards the Honda being the better machine for tooling around town. Its broader spread of power, and especially torque, means you can carry a gear for longer, but in practice the Honda’s gearing compared to the Z might negate that advantage.

Kawasaki's Z125 Pro is poised to take a big bite from Honda's pie. Looking at the specs, the two are similar in many ways.

Kawasaki’s Z125 Pro is poised to take a big bite from Honda’s pie. Looking at the specs, the two are similar in many ways.

These dyno numbers further prove the Honda and the Kawi are so closely aligned. They weigh practically the same at 225 lbs, make similar power, and are within $200 of each other. Of course, we won’t know for sure how the two bikes will stack up side-by-side until we put them against each other. We’re working on that now, but in the meantime feel free to chew over the dyno numbers above and speculate on which you think the winner would be in the comments below.

  • john phyyt

    How . Exactly .Do you go about recalibrating a butt dyno ? Evans: This seems like a task for you. Another technical article with diagrams and graphs would be helpful.

    • Starmag

      I’m pretty sure I don’t need a diagram of Troy’s butt.

      • TroySiahaan

        Well this derailed quickly…

    • http://www.motou.info Gabe Ets-Hokin

      Whatever happens, never ask Sean Alexander to re-calibrate your butt dyno. Just don’t.

      • http://www.motorcycle.com/ Sean Alexander

        You asked.

      • Doug Erickson

        as long as you don’t include any discussion of stroke and bore on that single thumper

  • Old MOron

    Hey Trizzle, how come we’ve never seen footage from that chest-mounted GoPro?
    Seems to me that you might have some good footage.
    http://motorcycle.com.vsassets.com/blog/wp-content/uploads/2013/09/2014-Honda-Grom-WING4798.jpg

    • TroySiahaan

      I don’t remember, but that might have been the GoPro that fell off the R1 I was riding in the fast lane of the 405 freeway several moons ago. Right around the time this pic was taken, probably.

      • http://www.motou.info Gabe Ets-Hokin

        Fonzie lost a camera there, too!

  • DickRuble

    I don’t think the dyno test is conclusive. The difference, while large in % is rather small in absolute numbers, and we don’t know what the margin of error for the dyno is. You need to test the bikes on the same dyno, the same day. The same way you do the head to head comparison. Ideally you would test three Kawas and three Groms and get the average for each group, then compare. To get a quick idea, you should compare two of the same bike. If you see differences, then you know you need a bigger sample than one.

    • GearDrivenCam

      Dick – you’ve raised some good points. I just assumed that these bikes WERE tested on the same dyno on the same day. However, it appears that they used a Grom data from a previous run. In addition – you would want to make sure that each bike was broken in, as most engines seem to be tight when new, and appear to free up a bit of power with some miles under them.

      And it would be great to have a sample of bikes dyno’d so we could get the average for each group and do a statistical comparison to see if the differences were likely to be due to chance. I’ve never seen that done though – and would be lots of work. What some testers do is run the same bikes for – maybe 5 pulls and then take an average of all the pulls. Then compare it to an average obtained from a different bike that’s completed the same number of pulls. At least this is one way to take into account for the variability that might exist from one pull to another.

      Regarding the reliability of the dyno results – at least one other dyno has been done comparing the Honda Grom and the Kawasaki z125 and it yielded a very similar results to what is shown above.

      http://www.gromforum.com/forum/2014-grom-general-discussion-forum/36425-2016-grom-dyno-vs-2014-grom-vs-2016-z125-pretty-impressive-new-grom.html

      • DickRuble

        Variability between pulls is one thing and i hope they did at least three runs. I suspect that there is a bigger variability between units though. However, the test from your source pretty much settles the question

  • Jeff Keene

    This is the most adorable spec waiving contest ever.

  • JMDonald

    I still have nightmares about my Captain America helmet. Seeing one on the Grom rider has damaged me. I am not sure I can recover.

    • TroySiahaan

      That Grom rider is me, and… you’re welcome. Check out the shades I’m wearing, too. They’ve got the Alpinestars logo on the lenses. 😉

      • JMDonald

        In high school my regular helmet was stolen and my backup was a Captain America. Weather permitting I rode to school and was teased incessantly about my helmet. It took a couple of months for me to save up enough to buy a new one. I never looked as cool as you do on the Grom but Alpinestars shades were not available at the time or I might have given you a run for the money. I’d proudly wear a Captain America today but I am old and don’t care anymore. The quality of your helmet looks a lot better than the one I had. I think I bought it at a Western Auto. Looking back on it I did look pretty cool wearing it when I rode my Mini Trail. I was a lot younger then.

  • Vrooom

    This is the perfect bike to buy for my wife. She doesn’t want a bike, but would think it’s cute, and let’s face I’d actually ride it to “Keep the battery charged”. Don’t tell her about trickle chargers.

  • Mahatma

    Who knew that a honda would be beating a kawasaki in the HP department.Wonder if honda consider releasing a 250 version with another cylinder glued on the original?Would seriously consider buying one even considering I’m on the wrong side of 50.

  • http://www.tanshanomi.com Tanshanomi

    If you’ve planning a shootout, I would love to see the Kymco K-Pipe included, too.