MotoGP classes

Discussion in 'Motorcycle Racing' started by Julian Bond, Aug 5, 2007.

  1. Julian Bond

    Julian Bond Guest

    From a purely engineering perspective, it might be worth looking at how
    much power is needed in each class and working back from that. Right now
    we have
    - MotoGP ~210bhp - 148Kg
    - 250 ~110bhp - 100Kg
    - 125 ~55bhp - 80Kg

    A prototype 500-2 engine based on the old 990 MotoGP engines ought to be
    able to make 110-125bhp fairly easily. The current MotoGP engines are
    more exotic as the factories chase revs so a 100BHP 400-twin looks
    possible but expensive. 110BHP from a 600-4 is easy and might not
    require any tuning of a stock engine beyond a pipe. From there we could
    have anything from 120 (US Superports), 135 (WSS), 150(unlimited
    tuning). Current YZF250s are making ~40BHP in tuned MX trim. ~45BHP
    looks possible in road racing trim with the same engine. A prototype 250
    single might get to 50hp. That's at least in the same ballpark as
    current 125GP.

    What would Ducati do? Well they built the Supermono as a V-Twin with a
    fake upright cylinder replacing it with a balancing rocker. So they know
    how to build something by just removing the top cylinder from a
    desmosedici. And you have to figure they could build a Supermono layout
    250 using the same top end layout.

    All of this assumes that we need to keep to the 1-2-4 ratio between the
    classes on horsepower and capacity. But that's only a relic of the old
    125-250-500 two stroke classes. Maybe 80hp-140hp-200hp would be a better
    progression. On that basis, 400-4, 600-4, 800-4 would make more sense.
    If production engines play a part, there's an added wrinkle. The
    Japanese have just dropped the power limits on their licensing scheme so
    that 400 road bikes are no longer limited to 55BHP. It's quite possible
    that in the next couple of years we'll see them building slimmed down
    400-4s with 70bhp or so for the home market[1]. Allow WSS or slightly
    above levels of tuning in prototype chassis on both these and 600s and
    we have a formula. So we'd have production based 400 with WSS tune.
    production based 600s with WSS tune + unlimited cams and compression
    ratio and 800 prototypes for MotoGP all in prototype chassis. Then put
    in weight limits and fuel limits to put a cap on expensive materials and

    Which then brings in Dorna vs FGSport. There's some sort of agreement
    that FGSport are the only people allowed to run world championships
    using production based machines. But it's not clear what form that
    agreement actually takes.

    And then finally, there's the factory vs private team issue. I don't see
    prototype chassis as being a problem. There are plenty of chassis
    builders out there and all the suspension bits are available off the
    shelf. Engine tuning is interesting. I think it should actually be
    easier for a private team to get competitive power with a production
    based engine than with the current 125-250 two strokes. And then there's
    electronics. Right now, traction control is hard and expensive. Even
    with 80hp-140hp the top teams will want to run it. You can see this as a
    good thing as it'll promote trickle down of the technology. Or a bad
    thing because it's where the factory budget can make a difference.

    [1] The EU is also looking at a similar graded license. Some markets
    already have a 33hp limit for 2 years after passing your test. A 400cc
    limit would be much easier to enforce. And I for one, look forward to a
    new batch of grey import 400-4s. I think these make a much better first
    real bike after learning on a 125 than a 600. It was quite scary enough
    watching my son jump from a 125 to a 15 year old 400-4. The current crop
    of 600s are *way* too much for the average 20 year old road rider.
    Actually they're way too much for the average born again 45year old as
    well. But that's got nothing to do with racing.
    Julian Bond, Aug 5, 2007
    1. Advertisements

  2. Julian Bond

    Julian Bond Guest

    Luigi Dall'Igna. Aprilia's race chief.
    At the moment Aprilia is thinking about MotoGp and Superbike. Our future
    is not in 125 or 250. For sure our race department is currently two
    sroke but our future is four stroke. I would like to re-instate the link
    between the classes, 800c four, 400cc Twin and maybe with in the future
    200cc singles.

    On 600s. I think this engine is not so good, it cannot be adjusted. The
    current 250s are a very good class for learning how to get to a very
    good level, the bike must not be easy to ride. The history is not the
    important thing, but the cost of racing is an issue, and anyway who
    would make all the chassis.

    Satoru Horiike. MD of HRC.
    I can only give you my personal opinion as Honda does not have any
    official proposals right now. The 800cc engine is very very special. but
    I think 500 Twins would be cheap and would make enough power to replace
    the 250 two strokes. You would be able to make a 250 single from this
    engine for a starter cass too. The current role of 250s as a class for
    riders to step up to MotoGP is very important, and the 125s are
    important as a starter, so a 125 four stroke single could be a
    production racer. We need to make sure these classes are not expensive
    and I think this would be a good way.

    I know of a proposal for a 600 four but this is a Dorna suggestion not
    an MSMA one. For my personal view this means prototype bikes and I think
    for KTM and Aprilia is would be very difficult.

    Harald Bartol. Technical director KTM.
    The four stroke thing is a political decision. I believe Honda is
    pushing the 600 idea, but there is no European manufacturer with an
    engine like this. To find a class with the same performance as a 250
    without an increase in costs - This is not easy.
    Julian Bond, Aug 5, 2007
    1. Advertisements

  3. Julian Bond

    Julian Bond Guest

    Lots of talk about this at

    I can't say I saw anything new in all that. I did see a bunch of people
    suggesting things that were frankly ridiculous. It seems to break down
    to 3 possibilities.


    500 Twins
    250 Singles

    400 Twins
    200 Singles

    400 - fours
    200 - twins

    It seems to me you can approach this from two angles.

    1) Try for an orderly transition with the new and the old side by side.
    In which case you start from 250 and 125GP and build something the same
    power and weight but four stroke. That pretty much means twins and
    singles either based on last year's or this year's MotoGP bikes. 55hp
    from a 200 single is really pushing it. But it's just about within reach
    starting from current MX engines. This year's MotoGP are more exotic and
    more expensive than last year's so at least to start with 250-500 makes
    more sense. But that leads to spec rules that limit the technology. Like
    rev limits.

    2) Jump to something different in one go. The 1-2-4 capacity ratio for
    the classes isn't set in stone. There's an argument for a 1-1.5-2 ratio
    between the classes so the progression and jumps are less extreme and
    each class is better preparation for the next. In which case 400-4,
    600-4, 800-4 might be easier. But prototype engines in the smaller
    classes will cost just as much as MotoGP which means production based
    engines. Which then means fine tuning the rules to make it work. But at
    least you can fine tune the rules.
    Julian Bond, Aug 8, 2007
  4. Julian Bond

    sturd Guest

    Julian Bond says:
    You ridden a stock 250 four stroke MX bike lately? They have
    powerband (for a 250), are pretty dang reliable, and make 40ish
    horsepower on top. Will go from zero to over a 60 foot double
    in 30-40 feet. A roadracer version (limited powerband, factory
    involvement, and exactly one weekend reliability) should do 70-75
    Minus 50cc and you'd easily do 55 HP.

    I think.

    Go fast. Take chances.
    Mike S.
    sturd, Aug 9, 2007
  5. Julian Bond

    Julian Bond Guest

    I don't know. I reckon getting from 40hp to 50hp from a 250 single is
    going to be tough. I severely doubt a 250 single could get to 70. Go and
    look at (mini)Supermono. The 450s are only getting 65-70. In the big
    class you need to go over 650cc before you can exceed that. The problem
    with singles is that there's no exhaust tuning to be had between
    cylinders. Or take MotoGP from last year and divide by 4. 60HP? Now
    imagine an out of balance single at 17k RPM.
    Julian Bond, Aug 9, 2007
  6. Julian Bond

    Julian Bond Guest

    Not Supermoto, Supermono. Road racing class for singles. For a long time
    they only had one rule "Single cylinders only". These days it's a bit
    more controlled and they have 450cc (MiniMono) and unlimited. The
    MiniMonos mostly use 125GP chassis. The MiniMonos turn lap times very
    close to 125GP.

    Here's the UK association

    In the USA AHRMA supermono/Sound of Singles but I can't find a website.

    A good example is
    Owner: Cedric Smith (USA)
    Engine: Honda CRF450R
    Chassis: Honda RS125
    BHP: 61 RWHP @ 9,500RPM
    Weight: 82kg

    Now that's based on an MX engine. There'd be more to come from a purpose
    built prototype. And yes with less power you can get away with a tighter
    powerband. And with a 250 you could get more peak revs. But I'm still
    really dubious about anything over 240BHP per litre from a single. More
    so because nobody has ever built one so there's nothing to compare.

    I'll ask around on the motorcycle-engine list.
    Julian Bond, Aug 9, 2007
  7. Julian Bond

    sturd Guest

    Julian Bond says:
    When you put it that way, I gotta agree. Then the question is "Is
    60 HP enough for a 175 pound GP3 bike?"

    Go fast. Take chances.
    Mike S.
    sturd, Aug 9, 2007
  8. Julian Bond

    sturd Guest

    Mark N asks:

    Ever ridden a mini bike?

    Go fast. Take chances.
    Mike S.
    sturd, Aug 9, 2007
  9. Julian Bond

    sturd Guest

    Mark N never went at it in anger on a race bike apparently:

    None of those have anything to do with racing. Riding (well,
    abusing) a mini bike does.

    Go fast. Take chances.
    Mike S.
    sturd, Aug 9, 2007
  10. Julian Bond

    Alexey Guest

    Back on topic. If I'm not mistaken, current minimum weight rules in
    125 and 250 GP classes apply to bike and rider in combination. So the
    important thing is not to be light, but to be aerodynamic. Yes, size
    has something to do with it, but not as much as when you're just
    trying to get the weight down.

    As far as the power is concerned, I don't find it that strange to be
    talking about realistic numbers. Over 65 hp from a four stroke 250cc
    single is pretty impressive. But personally, I don't think it's
    really that important what the peak power number will be, so long as
    the grids are full and the racing is close. Having raced in ~60 hp
    classes, I'd say watching 30 fast kids from around the world on tuned
    up little singles is gonna be a good show.
    Alexey, Aug 16, 2007
  11. Julian Bond

    Julian Bond Guest

    125GP only. 250GP has a minimum bike weight limit but not bike plus
    Me too! Somewhere between 50 and 80hp in a very lightweight pure racing
    bike seems about right to me.
    Julian Bond, Aug 16, 2007
  12. Julian Bond

    Mark N Guest

    As Julian said, there is no bike/rider minimum in 250. And the weight/
    size of the top guys in that class today suggests that size matters,
    and a lot - my guess would be that there has never been such a group
    of riders so small at the front in the history of 250 GP. Regarding
    125, what matters is what that minimum is, and relative to the bike
    weights. If the effective rider minimum still leaves a guy of normal
    size horribly overweight on a package basis, then it's doing no good
    at all. Based on who I see in 125, that's probably the case - I really
    doubt those 120-pounders are running up front with 25 pounds of
    ballast on their bikes.

    Regarding aerodynamics, as Hayden/Pedrosa have shown us this year in
    MotoGP, if weight is an advantage and little guys have that, then the
    bikes end up being designed around their size. So a bigger guy might
    not have a serious aero disadvantage on a theoretical basis, but in
    the real world the bikes are just too small for him. Given that the
    Honda 250s have been ridden by guys like Katoh, Pedrosa and Dovisioso,
    I really doubt they are close to sized for normal-sized guys. Shit,
    Elias, all 5-4 and 125lbs of him, complained the bike was too small.
    To each his own, I guess. Me, I think something like that is fine in
    national championships, but it has no place in GP. Guys who race there
    should already know how to ride, they shouldn't have to learn basics
    at that level, and I also don't think world championships are the
    place for kids. As for the "around the world" part, what is the makeup
    of 125 and 250 today? In 125 there are only two riders from outside
    Europe, I believe (Bonsey and some Jap), and I would guess that the
    majority are from Italy and Spain. So how do you change that?

    I think if you're going to call the support classes world
    championships they should be that, and not some training ground. And
    if they are a training ground, is it really the case that whatever
    teenage midget manages to come out on top on a 175lb, 60hp bike is
    likely the one best qualified to race a 335lb, 210hp machine in a few
    years? I have my doubts. If they're not a training ground and are
    supposed to be a world championship, then the machines should be more
    challenging and relevant. That's my opinion, anyway.
    Mark N, Aug 16, 2007
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.