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Thread: Derbi GPR Track Bike

  1. #31
    apriliaforum expert scottydog's Avatar
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    Cool I haven't surfed this forum in over a year I'd think! Got some catching up to do! lol
    Currently

    Honda MBX, Dream 50, Solo 50, NSR, CBR 150
    Moriwaki 80, Derbi GPR50

    In works

    Honda NSR (SP)
    Honda RVF150R / NR150 custom

    Previously

    Kawasaki AR80
    Honda RS125

  2. #32
    apriliaforum expert ToraTora's Avatar
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    Cool Bikes is Bikes, and then there's Bikes!

    Scott! It's great to see you posting again. ;D

    freedomgli,

    It's amazing what some people bring to the kart tracks. Sure there are lots of Motards out there with huge 4T ugly sounding engines, but this weekend there was even a Ninja 250 out there (you can guess why I didn't take a photo of it!). But usually the tracks run different heats so that a pocket bikes doesn't have to compete with the big Motards and such. Although a couple weekends ago at the Sonoma track my friend Violet was out on her first lap, first corner, and a Motard ran straight into Violet crashing her out. That messed up the bike enough that it was the end of her day. On the track I kind of see Motards as SUVs. They ride like them, sound like them, are out of control like them. Just ugly.

    Nice find on the SG link. When Paul picked up the SG for his daughter I went looking around to find info on it too. There's precious little to be found. Mostly what I found was their pocket bike info. From what I'm told that is a water cooled 50cc engine with a six speed gear box. I heard that it was $13K. For that kind of money I probably would have sourced a MetraKit. But it's a cool bike--everything on it is quality, and I can't keep up with Emmy--not even close. :P

    I don't know who brought it in, but if you really want to know I can find out, and get back to you with the info.



    There's another kid named Max that comes out to these tracks with a Metrakit. It's a newer one with the Metrakit engine. Max has been racing in Europe is some sort of Metrakit class. He's been racing kids two years older--and yet they are smaller then him, and Max isn't a huge kid. We just grow them larger here in the States! Max has been getting on the podium which is fantastic. If you watched the Red Bull Rookies then you know that the Americans generally don't do very well in Europe. We don't have the support systems here in the States to groom young GP racers. So to see Max going out there, and getting on the podium is amazing. He's fast though. On the Moriwaki even Garret has to work hard to keep up with Max on the Metra 50.

    I'd really like to see the Cobra Dirt bike cats get into miniGP. They have an amazing two stroke engine that could be the platform for a great miniGP bike. Cobra makes a very competitive MotoCrosser built here in the States that's giving the Japanese, and even the European manufactures serious headaches. They do it by not following the Japanese 80/80 method. Which is give you 80 percent of what you want for 80 percent of the price. I mean that works, and it's a fantastic way to sell crappy Civics, but is that really what you want in a race bike? Anyway, the Cobra engine is sweet, and would be a little GP dream.





    The RS conversions though are probably the best bike for us older folks. It's a real GP bred race bike, and an 80ish engine is all you need at the cart track--well unless you are hunting Motards. Speedy has a KX100 engine in his RS. It's probably the nicest of the RS bikes out there.


  3. #33
    apriliaforum expert mattology's Avatar
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    The Honda rs chassis is a tight fit for anybody over 5'6, Jesus Christ, the aprilia rs50 is bigger

    Get your confidence back with Aprilia.

    caution: the use of motorcycles may be habit forming. side effects include purchasing multiple examples of the same bike, in different states of tune, different years, or different models altogether. some motorcycles may be not running when purchased. some parts are no longer available. there are rare instances where aprilias are bought over the internet and upon arrival, they are not as were originally disclosed. there is a small group of people who cannot handle two stroke engines and motorcycle maintenance. if this is the case, you may not be a candidate for Aprilia RS250's.

    Aprilia. Ask your doctor if the RS250 is right for you.

  4. #34
    apriliaforum expert ToraTora's Avatar
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    Wink Stature

    It's true that GP racing tends to favor the jockey body types. :P

    But the reason the GP RS is better than the road RS for the track is that it is much lower to the ground. Look at the photo of Speedy on his RS. To get a GPR, or an RS50 like that in the corner requires a lot more effort. I'm not saying that you can't have fun on these bikes, hell my "track bike" is a GPR, but the GP bike stature is just better at the track than the Replica bikes.


  5. #35
    apriliaforum expert ToraTora's Avatar
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    Wink More Fun at the Track

    Found some of the Moped action that's been happening, and a photo from Sonoma back in 2013 when I took the Monza to the track.

    These are a couple of race mopeds. The white one is a Derbi Variant, and the black one is a Derbi Revolution. These bikes are screaming fast. Not your grandma's mopeds. They were actually able to out ride Garret when he was one the Kayo at the race last month.



    Here we have me with the Monza, MT Mike with his RS80, Speedy with his RS85 (it's now got a KX100 in it), and Paz with his RS250F!


  6. #36
    apriliaforum expert mattology's Avatar
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    Quote Originally Posted by ToraTora View Post
    It's true that GP racing tends to favor the jockey body types. :P

    But the reason the GP RS is better than the road RS for the track is that it is much lower to the ground. Look at the photo of Speedy on his RS. To get a GPR, or an RS50 like that in the corner requires a lot more effort. I'm not saying that you can't have fun on these bikes, hell my "track bike" is a GPR, but the GP bike stature is just better at the track than the Replica bikes.

    sure, the height has some to do with it, but it's the entire package. the gp bikes weigh like 160 pounds, it is ridiculous. my rs weighs 204 lbs and the road 125's weigh almost 280, don't they!? so they are smaller, they are lower, they are significantly lighter, they have more aggressive frame geometry, their frames are stiffer, the whole package is a step up. if you were to take a street RS and lower it would it improve that much? I lowered the front end just a little bit and raised the rear to get the bike to turn a little nicer, but i'm not sure how much of an improvement it was because the bike went from going around the outside of ninja 250s at the track to still going outside ninja 250s at the track.. so it's like, great, i don't have logical laptimes, i'm still in like the 1:40's or whatever, not really that great.

    Get your confidence back with Aprilia.

    caution: the use of motorcycles may be habit forming. side effects include purchasing multiple examples of the same bike, in different states of tune, different years, or different models altogether. some motorcycles may be not running when purchased. some parts are no longer available. there are rare instances where aprilias are bought over the internet and upon arrival, they are not as were originally disclosed. there is a small group of people who cannot handle two stroke engines and motorcycle maintenance. if this is the case, you may not be a candidate for Aprilia RS250's.

    Aprilia. Ask your doctor if the RS250 is right for you.

  7. #37
    apriliaforum expert ToraTora's Avatar
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    Cool Physics is Physics

    Sure it's the whole package. One is a GP race bike, and the other is a replica street bike for Sixteeners. :P I don't know what the Aprilia street RS125 weighs, but my Cagiva was pretty heavy. The wheel upgrade helped a lot though.

    Did you ever read that Moriwaki vs the Aprilia RS125 shootout Motorcycle.com wrote? The RS didn't have a chance, and it lost in every way, except retail price. It's a street bike that some asshole decided to pretend was a track bike. And well it suxors on the track, as one would totally expect. Way too heavy, not enough power for the weight, and the CG is way too high. The RS50/GPRs suffer from very similar issues. So really they don't make "good" track bikes. But you can have fun on them at the track, and the cost of entry is very low.

    Out at stockton if I were to race my GPR I would be in the same class as the Moriwaki. 33 real horse power against the little Derbi--the Derbi wouldn't have a chance.

    With regards to lowering the street bikes, It wouldn't work because you'd screw up the geometry. If the swing arm doesn't have at least a slight incline from rear to front the suspension suffers greatly. Now if you chopped up the frame to put the rider lower that would be an improvement, but almost no one goes about lowering a bike that way, they nearly always do it by fuxoring the suspension.

    But the lower bike has a huge advantage. When I took my moped, which is big for a moped, but about the same rider height as the RS race bike, it was much easier to navigate the kart track than on my GPRs. The GPRs have a much higher CG, and without speed to deal with it like what the MotoGP bikes have, it's hard to get the higher CG to navigate the lean angles that you can get with the smaller bike, at the lower speeds.

    Note that this Motorcycle.com test is bullshit because it's not really comparing the 4T with the 2T, it's comparing a GP bike with a Street bike--on a track! They admit it in the video at the end, but still I hate this sort of sensationalism. If an honest to goodness 2T vs 4t comparison were to be done the 2T would shine on the track. Physics is physics.


  8. #38
    apriliaforum expert ToraTora's Avatar
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    Wink Bikes!

    Found some more photos from 2013. Here's MT Mikes' RS, Speedy's RS, and Violet's NSR.






  9. #39
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    Those cobra motors seem really legit for under 100cc! Do you have any pics of you on the derbi?
    2005 Rs50 Rs4/GPR clone

  10. #40
    apriliaforum expert scottydog's Avatar
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    The Honda RS125 track bikes is pretty serious along with the others in it's class. I used to have one as well as had time on the TZ125 also. The powerband on those GP bikes is pretty fierce. My RS was a 96 with 97 pipe and other bits.

    When I sold it I kept a set of wheels with the rains on them. Idea is to fit them to my Moriwaki 80 at some point.
    Currently

    Honda MBX, Dream 50, Solo 50, NSR, CBR 150
    Moriwaki 80, Derbi GPR50

    In works

    Honda NSR (SP)
    Honda RVF150R / NR150 custom

    Previously

    Kawasaki AR80
    Honda RS125

  11. #41
    apriliaforum expert ToraTora's Avatar
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    Dcrac3r, it looks like a great engine. And they are made in the States too. If Cobra started building miniGP action it would carry a lot of weight, because of the success they've had in the dirt. We really need that sort of thing in the States.

    Scotty that 80 you have is pretty slick, but yeah the RS is a real race bike.

  12. #42
    apriliaforum expert ToraTora's Avatar
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    Wink Chasing the bits

    I've been working on another project which I'll probably start posting about tonight. While going at it I found some bits for the track bike. I sadly admit my bike isn't up to spec yet. I have some things to do like catch bottles. Thankfully I found them tonight. I also found some nice Malossi reeds, and a silencer that's better fitted for the track--it's going to need some cleanup, and probably a repacking too. The carbon Jolly Moto is just too nice for the track.






  13. #43
    apriliaforum expert mattology's Avatar
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    HRC catch can?

    Get your confidence back with Aprilia.

    caution: the use of motorcycles may be habit forming. side effects include purchasing multiple examples of the same bike, in different states of tune, different years, or different models altogether. some motorcycles may be not running when purchased. some parts are no longer available. there are rare instances where aprilias are bought over the internet and upon arrival, they are not as were originally disclosed. there is a small group of people who cannot handle two stroke engines and motorcycle maintenance. if this is the case, you may not be a candidate for Aprilia RS250's.

    Aprilia. Ask your doctor if the RS250 is right for you.

  14. #44
    apriliaforum expert ToraTora's Avatar
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    Red face Water Bottle

    I bought a bunch of parts from Todd--he had bought out all of the Rocket Ranch bikes. Lots of strange stuff showed up. I've been enjoying the bits from that haul for years, as have my friends. :P Although the bottle could have come from somewhere else too.

    Yes all of that, and more fit into the Saab.


  15. #45
    apriliaforum expert mattology's Avatar
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    Get your confidence back with Aprilia.

    caution: the use of motorcycles may be habit forming. side effects include purchasing multiple examples of the same bike, in different states of tune, different years, or different models altogether. some motorcycles may be not running when purchased. some parts are no longer available. there are rare instances where aprilias are bought over the internet and upon arrival, they are not as were originally disclosed. there is a small group of people who cannot handle two stroke engines and motorcycle maintenance. if this is the case, you may not be a candidate for Aprilia RS250's.

    Aprilia. Ask your doctor if the RS250 is right for you.

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