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Thread: 250r to 380r monster

  1. #1
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    250r to 380r monster

    This idea is finally becoming reality. A few years ago 1upfront bought a cylinder from an odyssey 350 with the intention of putting it on an aircooled 250r. Since then we have kicked around a few other ideas and he finally decided to go forward with this project.
    It will be using the odyssey cylinder bored to 82mm and to top it off it will be running a crank from an 85 250r to give it a 72mm stroke. He had the cases bored so the crank and the jug would fit. and had the crank machined down on the ends to match the aircooled crank specs. It still needs a few small mods but it is shaping up.





    This is with half of the crank in with the piston and jug attached to check for fitment. The piston comes right to the top of the cylinder like it should but the cases will need to have a little more taken out because the piston skirts hit the cases on the down stroke. It won't take much though.







    These cases are for mock up only they were junk but he didn't want it ruin a good set if it didn't work out.
    Appalachian American Racing
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    Appalachian American Engineering



    "Can't", never could do nothing



    There's nothing like the sound of screaming 2strokes and the smell of race gas in the air

  2. #2
    Billy Golightly's Avatar
    Billy Golightly is offline Always finding new and exciting ways to not give a hoot in hell Catch me if you can
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    Awesome work guys. I love seeing stuff pieced together from different motors like that. It actually takes some skill and understanding of how things work instead of just throwing the bolt-in crap on there.

  3. #3
    Billy Golightly's Avatar
    Billy Golightly is offline Always finding new and exciting ways to not give a hoot in hell Catch me if you can
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    PS, were you guys already running a full circle crank? If not you should see some benefits from that as well.

  4. #4
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    Quote Originally Posted by Billy Golightly View Post
    PS, were you guys already running a full circle crank? If not you should see some benefits from that as well.
    No, he found this one on ebay for cheap. It needed to be rebuilt so it was the perfect candidate.
    Appalachian American Racing
    the home of
    Appalachian American Engineering



    "Can't", never could do nothing



    There's nothing like the sound of screaming 2strokes and the smell of race gas in the air

  5. #5
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    Here's a pic of both style crankwheels, I originally bought the liquid crank for comparison to see if it was even possible to use and found that the drive end/important end had identicle splines only longer so all we had to do there is have it wacked off, also the bearing size is the same and the splines are timed right for the counterbalancer not that it will be completely effective with such a large stroke lol, the flywheel key is timed right for the ignition timing too lol
    Stock crankwheel on right

    Here's a pick of both style crankwheels together it gives you an Idea of how much larger the stroke will be.
    Airfoolers RULE!!!

  6. #6
    300rman's Avatar
    300rman is offline My other user 3WW ID was Nitebiker07. Teaching quads a lesson
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    Quote Originally Posted by Billy Golightly View Post
    PS, were you guys already running a full circle crank? If not you should see some benefits from that as well.
    very true. my crank is a balanced full-circle, and it is definitely noticable.

  7. #7
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    Along with the crank and cylinder mod I'm upgrading the clutch to the 89 clutch upgrade with alittle machining to the 83 pressure plate and the throwout rod. Then I'm installing a new billitt basket on a welded/reinforced factory gear. Here's pics of the new parts.
    small washer not pictured


    Airfoolers RULE!!!

  8. #8
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    I have been looking to go bigger with my drag bike, but just cant seem to come up with a way that wont cost a ton in the long run.. I only get to run it at TF and maybe one other race a year so I realy dont wanna drop alot of cash on it. The Mugen's are way to rare and costly, and the 300's have way to many problems finding parts to complete them.

    If this is something that could be done and the cost is'nt to crazy id like to go this route myself.. If not Im always on the look out for a cr480.. So keep us posted on this im very interested..
    1985 250R Selveys port job and pipe
    1985 70 piped for lil'freaks
    2001 TRX90
    ATC 90+250R+BEER= Drag Bike
    1984 ATC70 Pit bike
    1984 110 for sale

  9. #9
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    Daddio and 1upfront, you guys rock!

    I just bought an 84 250r about 3 weeks ago to replace the one I sold 10 years ago. I was already looking for more power and bought a great FL-350 top-end on Ebay. I knew case machining would be required, but I didn't know anyone who had done it. I also didn't know that the later 250r crank would fit with mods.

    Then to top it off.....you two come up with an upgraded clutch basket too?

    Like I said, you guys rock! I am attempting this exact build, and would love to be able to consult with you two to get the benefit of your knowledge and experience.

    It ironic, I was just going to try to contact you 1upfront, to see if you had tried this yet. I guess I know now!
    1985 ATC 250R Project

  10. #10
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    Here's the intake and carb I'll be running it's a 40mm lectron with oversizes bowl and a sand scorcher intake, I'll just buy a 40mm boot for the intake and port it to match.

    Last edited by 1upfront; 02-21-2009 at 11:27 PM.
    Airfoolers RULE!!!

  11. #11
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    if you can get that to work that's one badass setup
    A Rental Car is the only true all-terrain vehicle.
    " I actually think it is good that you have clubs where people can go and enjoy riding these things together. It reminds me of how the prisoners on death row have fun waiting for their turn on the electric chair. Fair enough, the trike isn't an electric chair, but it is about as safe and comfortable as one."

    http://www.nps.gov/bicy/

  12. #12
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    Quote Originally Posted by bigpimpin View Post
    if you can get that to work that's one badass setup
    I have little doubt that it will work. I'm more sure now than I was a month ago. After a little more machine work it will be ready to send out for port work.
    Appalachian American Racing
    the home of
    Appalachian American Engineering



    "Can't", never could do nothing



    There's nothing like the sound of screaming 2strokes and the smell of race gas in the air

  13. #13
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    Quote Originally Posted by Daddio View Post
    After a little more machine work it will be ready to send out for port work.
    May I ask who you will have perform the porting work. Flotek maybe. Were you happy with the port work they did on the 300.

    (sorry for the bad punctuation. My question mark key quit working on my laptop.)
    1985 ATC 250R Project

  14. #14
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    Quote Originally Posted by Enginerd View Post
    May I ask who you will have perform the porting work. Flotek maybe. Were you happy with the port work they did on the 300.

    (sorry for the bad punctuation. My question mark key quit working on my laptop.)
    Yeah Denny at Flotek does my portwork, headwork and flywheel lightening he does an excellent job.
    Airfoolers RULE!!!

  15. #15
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    Quote Originally Posted by 1upfront View Post
    Along with the crank and cylinder mod I'm upgrading the clutch to the 89 clutch upgrade with alittle machining to the 83 pressure plate and the throwout rod. Then I'm installing a new billitt basket on a welded/reinforced factory gear.
    I have a question about your Mitaka clutch basket. Can you tell me what application it is for, and where you bought it? I am guessing its for an 86-89 TRX 250R?!?!

    Thanks sir.

    EDIT: I found these posts here and on .ORG

    http://www.3wheelerworldforums.com/s...ad.php?t=84453

    http://www.3wheeler.org/vb/showthread.php?t=32872

    So.....I now know its original application is a 78-80 CR250, and it came from here: http://www.grampianmotors.co.uk/

    and it uses the same plates as a Honda 300EX Quad.

    My new question is: Did you ever have those +3mm clutch rods made? Also, can you elaborate on the parts and machining required to use this basket and plates in an air fooler?

    Thanks again!
    Last edited by Enginerd; 03-05-2009 at 12:41 PM.
    1985 ATC 250R Project

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