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Thread: GPR250 (project)

  1. #1
    apriliaforum Junkie -CON-'s Avatar
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    GPR250 (project)

    I guess it's time for me to shout. So finally I got my 250cc engine from YZ Yamaha.
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    Last edited by -CON-; 12-22-2009 at 07:09 PM.
    2005 GPR50 metrakit pro-race 70, race crank, pro-race pipe moded with side/belly bleed, 24mm PWK, Carbon fiber reed, Malossi ignition TC UNIT K15, stock flywheel with cut of starter gear. 16 teeth front sprocket. Max speed reached 121km/h.
    2005 DERBI GPR50 with YZ250 engine http://www.apriliaforum.com/forums/s...d.php?t=179679

  2. #2
    apriliaforum Junkie AF1-Racer's Avatar
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    lol... that will defiantly take some modification to fit and to run..
    lot of welding and grinding...

    what kind of exhaust are you going to use to make it run? (custom build?)
    My bikes:
    Aprilia AF1 Sintesi
    http://www.apriliaforum.com/forums/s...d.php?t=175772
    AF1 to RVF conversion!


    Malaguti RST (SOLD)

    Quote Originally Posted by MasterTenerife

    Well, i have just looked at my bike, and the goddamn wheel spins both ways, is my engine broken now, after i redlined it today?

    Oh man, this gay, how much money do i need to fix it?

  3. #3
    i like the look of this seems siumilir to my project low weight chassis and big power engines fuck ya

  4. #4
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    Will that chasis and swingarm be alright with a 250 engine in?

    Looks bloody interesting mate, keep us all updated!

    Oh yeah, if I ever go to Canada, can I have a go haha!
    RIP Spike

  5. #5
    apriliaforum expert DanHam's Avatar
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    that rear brake looks worryingly small with that engine in lol, good luck with the fitting
    2004 Aprilia RS50 - Sold
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  6. #6
    apriliaforum expert bradders's Avatar
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    yeah, would go luck fuck off a shovel but sureley that will rip the GRP's frame to piss?

    just saw - it's a 2t. you should put the 4 in there :p
    91' NC30
    98' 306 Dturbo

  7. #7
    apriliaforum expert 46robbie46's Avatar
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    Looks cool, but is it illegal to ride in your country, at your age, with that engine in?

  8. #8
    apriliaforum Junkie -CON-'s Avatar
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    Yeah It is legal to ride any type of motorcycle at age of 16 if you have motorcycle licence and anyone could have at age of 16, cool isn't it !?! But what is not legal > it is not legal to insure motorcycle, at 50cc and have 250cc in it, that is called insurance fraud, and will get you a big ass fine, I am gonna have to re register or be very careful, I can go stupid on it !
    Last edited by -CON-; 10-04-2009 at 01:19 PM.
    2005 GPR50 metrakit pro-race 70, race crank, pro-race pipe moded with side/belly bleed, 24mm PWK, Carbon fiber reed, Malossi ignition TC UNIT K15, stock flywheel with cut of starter gear. 16 teeth front sprocket. Max speed reached 121km/h.
    2005 DERBI GPR50 with YZ250 engine http://www.apriliaforum.com/forums/s...d.php?t=179679

  9. #9
    apriliaforum Junkie AF1-Racer's Avatar
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    i'd put some bigger brakes with a 250.. maybe update your springs and put a other front forke in
    My bikes:
    Aprilia AF1 Sintesi
    http://www.apriliaforum.com/forums/s...d.php?t=175772
    AF1 to RVF conversion!


    Malaguti RST (SOLD)

    Quote Originally Posted by MasterTenerife

    Well, i have just looked at my bike, and the goddamn wheel spins both ways, is my engine broken now, after i redlined it today?

    Oh man, this gay, how much money do i need to fix it?

  10. #10
    apriliaforum expert bikebike69's Avatar
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    Dont get me wrong here I really love a good project. But it sure does seem like a lot of guys on here are forgetting that these bike really are SCOOTERS. The componets are not made to handle a lot of the power conversions folks are doing....not trying to be a wet rag but trying to save some of you a little grief later when things go bad,exspensive. "Just because you can doesnt mean you should" kinda thing. If this were mine I think I may go with a 80-85cc 2-stroke or 125-150cc 4-stroke. You will get alot more life from the bike. Just my .02

  11. #11
    apriliaforum Junkie -CON-'s Avatar
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    Isn't this bikes come with 125cc in them, the only thing is different front fork ?

    38mm carb, original size but not the carb!
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    Last edited by -CON-; 12-23-2009 at 03:35 AM.
    2005 GPR50 metrakit pro-race 70, race crank, pro-race pipe moded with side/belly bleed, 24mm PWK, Carbon fiber reed, Malossi ignition TC UNIT K15, stock flywheel with cut of starter gear. 16 teeth front sprocket. Max speed reached 121km/h.
    2005 DERBI GPR50 with YZ250 engine http://www.apriliaforum.com/forums/s...d.php?t=179679

  12. #12
    apriliaforum Junkie AF1-Racer's Avatar
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    And keep in mind there italian! (derbi is spanish but same mess) (= rubish altough good looking and funny)

    A 50cc frame is not super weak (scooters are) i guess they can handle up to 125cc with some modification. i know of Honda NS1's that have 125cc kit's and Honda MT50 and MTX.

    I always hear those horror story's about derbi frames (like new swing arms snapping in half) and poor welds.

    fun project but 250cc is really really pushing the limit and maybe going over it.

    the rear swing arm should be reinforced for the power of the 250. sprockets might need changing as well.

    125 Front forks and brakes are pretty much going to be a must.
    then you should also check if the frame can handle the weight and engine vibrations.
    My bikes:
    Aprilia AF1 Sintesi
    http://www.apriliaforum.com/forums/s...d.php?t=175772
    AF1 to RVF conversion!


    Malaguti RST (SOLD)

    Quote Originally Posted by MasterTenerife

    Well, i have just looked at my bike, and the goddamn wheel spins both ways, is my engine broken now, after i redlined it today?

    Oh man, this gay, how much money do i need to fix it?

  13. #13
    apriliaforum expert 46robbie46's Avatar
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    Quote Originally Posted by -CON- View Post
    Yeah It is legal to rite at my age of (25) with that kind of engine, it is legal to ride any type of motorcycle at age of 16 if you have motorcycle licence and anyone could have at age of 16, cool isn't it !?! But what is not legal > it is not legal to insure motorcycle, at 50cc and have 250cc in it, that is called insurance fraud, and will get you a big, ass, fine, I am gonna have to re register or be very careful, I can go stupid on it !

    For other of you, yes there will be a lot of mods and fabrication, exhaust have to be made (speaking of which if someone can help me to find a free software to figure out the measurements for the pipe that will work with my engines ports PERFECT, THANKS!) the frame should do OK, it will want to lift the front up, just gotta reinforces it a little on the top front mount, as for the rear fork, yeah I don't know about that, maybe it will get f*ked , but my biggest concerns are about the wheel and the rear sprocket, the sprocket is mount by six bolts size 8, and the area where it is mounted is kind of looking weak as well, cant drill and put bigger bolts in ether, that part is shity. So I am gonna to have to machine a custom rear sprocket that will fit also to the center of the wheel, which will help with the straight, also the kick start needs modifications and the shifter, but the shifter I could use same as they use on RS250 with the linkage, and I don't know how I am going to make the light work, because YZ is a racing machine not enduro so there is no light, other than that I don't know what other problems I might run in to, but I'll keep you updated!
    Ahhh cool, sounds like you've got a good deal there! Go easy on it though, will be a teeny weeny bit different to the 50cc you have in there at the moment.

    And i know what insurance fraud is! Patronising.....

  14. #14
    apriliaforum Junkie AF1-Racer's Avatar
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    Quote Originally Posted by -CON- View Post
    Isn't this bikes come with 125cc in them, the only thing is different front fork ?
    Not sure about that i have seen the new GPR 125 and it does look different.

    I know old Zundapp and Kriedeler mopeds head 125 frames (and brakes)
    Honda NS1 frame's are 125 NSR frame's with a 75cc engine.

    A lot of moped's do have a 70-80CC version with mostly identical frame's and brakes.
    My bikes:
    Aprilia AF1 Sintesi
    http://www.apriliaforum.com/forums/s...d.php?t=175772
    AF1 to RVF conversion!


    Malaguti RST (SOLD)

    Quote Originally Posted by MasterTenerife

    Well, i have just looked at my bike, and the goddamn wheel spins both ways, is my engine broken now, after i redlined it today?

    Oh man, this gay, how much money do i need to fix it?

  15. #15
    apriliaforum expert bikebike69's Avatar
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    cant speak of the new ones but the old Aprilia RS50 had no cush drive and small mounting bolts for the rear sproket. Just wondering if the power is to much for that type of wheel?

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