Inside the Honda NSF250R

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Last Thursday, we showed the first images and specs of the completed Honda NSF250R. The $38,200 Moto3 contender weights just 185lbs and puts out a shocking 47.6bhp and 20.6lb/ft of torque. To put that in perspective, the road-going Honda CBR250R weighs nearly twice as much while putting out around half the power. Now, here’s a look underneath that HRC bodywork and video of it in action.

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In this PDF and in the gallery, you’ll find shots of the all-new engine and the new frame, which is based heavily on the old RS125R two-stroke. The most revolutionary thing on the engine is the reverse cylinder, which sees the intake at the front and exhaust at the rear to optimize airflow, then cants itself back 15 degrees to optimize mass centralization. Check out just how beefy the frame and swingarm in comparison, despite the minimal weight, this is going to be a very strong platform.


  • michael uhlarik

    Beautiful piece of engineering.

    • Ducky

      It’s pretty obvious what the intention is behind this design: Simplify, and add lightness.

      It’s as basic as it gets, and very elegantly done… particularly the engine/intake/exhaust packaging.

  • Edward

    Thing looks like a damn pocketbike. It’s awesome though. I’m pretty shocked that it weighs almost half as much as the cbr250r. It would be cool to take a cbr250r and see how light and powerful you could make it. HFL project bike? Hmmmm?

    • Sean Smith

      Ha, I was answering your question as you were typing it.

      See below.

  • Sean Smith

    I’m going to attempt to nip this one in the bud: No, you can’t build a 185 lb, 40 hp, 250cc single cylinder street bike.

    If it was built with the intention of being sold in large volumes, they could probably get the price down somewhere just over a 250 mx bike, but you would still be dealing with race-bike maintenance. Think bi-weekly oil changes and new pistons and rings on weekends. Once a month, you’d get to go through the head and spend $800 on titanium valves, seals and gaskets.

    • aristurtle

      Right, the engine maintenance would be a bitch if you were keeping the engine the same. But could you build a race-replica version of this by keeping the weight, ergonomics, suspension, etc. essentially the same while subbing in the road-going engine from (say) the CBR250R (or something similar).

      I mean, you expect a race-replica bike to have less power, it’s the other stuff that I’m interested in.

      • Ducky

        Not likely. The engine has a 15 degree cant for a reason- the tire isn’t going to clear unless you use that specific engine.

        Look at the packaging as well: The intake and exhaust are miniscule, almost non-existant, and are heavily dependent on the engine’s cant (again) to position the intake for Ram-air effect. You won’t be able to do that with another engine in this frame.

    • michael uhlarik

      There is simply NO WAY that anything remotely similar to this could be manufactured and sold at a profit, for less than $30k. None.

      If you dumb down the swingarm, frame, engine and suspension components to a level that it could be retailed for “just over a 250 mx bike” money, it would weight 100lbs more, and nothing like the ride or performance envelope. What you see with the NSF250 is a very high quality, very high investment bit of design and engineering. A road version would be in name and potentially styling only… and even then…

      • fasterfaster

        I’m confused by your and Sean’s statements. Maybe I have different volume numbers in mind, but with the architectural work done, a consumer version of this bike could certainly be done for $15k or less… I’d say a lot less. Look to the Aprilia RS125 at $5,500, 33hp and ~300lbs wet in street trim. Surely Honda could match those stats (despite the 4stroke weight penalty) with an extra $10k to play with. If they believed there was enough of a market for volume production…

        • michael uhlarik

          Let me draw your attention to Exhibit A : the swingarm.

          It is made of multiple CNC milled aluminum parts, bearing fitments (requires precision turning), and most expensively, several complex stampings. Those stampings require tools (steel forms) and then must be cut, jigged in place and then welded. The whole swingarm is then placed in a jig for alignment, corrected, coated in an anti-oxidant and clear coated.

          Each of these steps is a separate operation, each requiring a skilled operator. If this was a part for a large volume product, like say a CBR600RR (sales volumes over 50,000 units per year) then it MIGHT be feasible froma cost point of view. We used to make swingarms on FZR’s and such this way, but it was just way too expensive. On a ultra low volume 250 street bike (say less than 5000 units/year) there is no way you could make this work, not even in Japan, not even Honda. Now look again, this NSF has milled aluminum parts everywhere, a high cost, hand assembled motor, etc. TO make a street bike version, it would have to have 80-90% carry over parts from existing street bikes, and that means high weight, low performance (relatively).

          People just have no idea what things cost. I am not trying to be negative, I want these bikes on the road too, it’s just a fact.


          • fasterfaster

            With all due respect, it can be done. I know because we are doing it (in a different segment, but analagous).

            Like I said, the architectural work is done, but the parts would have to be reengineered for cost and volume. Even at 5000 units, this is quite feasible. That swingarm could be done with a third the part count and simpler operations – the weight penalty wouldn’t be 2x, it would be 15-25%. The machined components could be cast or forged depending the geometry, and designed for single machining fixtures. Weight penalty, probably close to zero for the forgings, maybe 15-25% for the castings.

            Whether it’s worth Hondas effort for a bike that won’t be a blip in their top or bottom lines… That’s a different question.

            Drop me a note and we can follow up offline.

    • eric

      This kind of thing has been around for quite some time. DIY race bike BRRAAAP!

  • Gene

    Damn, I’ll bet that thing would be FUN!! (just before it highsides you far enough that NORAD starts tracking you)

    • Barry

      Hey, it can’t be as dangerous as the previous generation 125′s when it comes to high-siding you… “oh noes! I’m off the pipe and I’m losing feet per second on the guy ahead of me! WOT. Bog… bog… booooggggg… DING! Aiiyeee! *brown blue brown blue brown red brown black*”

  • Ducky

    It might be my imagination, but those wheels look the exact same as the CBR125R’s. 90/120 section tires 0_o

    The engine packaging is my favourite part of the bike.

  • Richard

    Is there a link where one can download the PDF without issuu issues?

    • Scott-jay

      Here’s link: []

      • Richard

        Thank you Scott-jay.

  • Kit

    Compare it to the current weight and power of a GP spec 2-stroke 125 and you can see why the GP paddock is, in general, underwhelmed by this ‘replacement’. It will also be extremely interesting to see how Dorna allocate grid slots, given the bike is less than 15% the price of a current 125.

    More interesting is the rumour that their will be a dedicated 2 stroke championship (125, 250 and 500) starting up in Spain. There are plenty of mechanics, tuners, riders and recently retired bikes itching for this true …

    • fasterfaster

      The price is pretty fantastic. Nothing comparable that I can think of… Do you think they’ll sell you one if you don’t have a race team?

  • Barry

    In the parlance of the webs: Do want. It’s obviously a sign of my track sickness that the price seems totally reasonable for a kick-butt small displacement race bike. The KTM 125 GP bikes were more than this if I recall, and they were monstrously cheaper than the next more competitive 125(you’ll observe that nearly nobody bought the ktm’s in spite of sub-month availability to the States). I seem to recall 40k being about the entry to a brand-new all inclusive competitive GP bike, but that may be off. I’ve slept and drank beer since the last time I priced one.

  • Roman

    Man, Honda’s still got it…

    • fasterfaster

      When they carve off a small team of focused rider-engineers with a well-defined application, yes, they can still kick ass. Give them a squishy, broad problem to solve with a committee of marketers and multiple engineering teams… it’s a different story.