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Thread: VT250 v-charge potential?

  1. #1
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    VT250 v-charge potential?

    For a while I've been intrigued by the idea of using one cylinder to supercharge another. Since I've got a VT250F2 I don't use, figured I could sleeve down a cylinder to 100cc, then use the other 125cc cylinder to force feed it. Would need to get new cams or swap a head for reed valves, sleeve and machine a new piston with the right weight, plus the plenum and efi etc.

    Thoughts? Would it even meet the rules?
    "A shark on whiskey is mighty risky, but a shark on beer is a beer engineer" - Tad Ghostal

  2. #2
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    Not sure about the rules etc but have a read of this if you haven't already, very interesting read.
    http://www.customfighters.com/forums...ad.php?t=39520

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    Hard to do well and it'd finish up pretty heavy with a lot of internal friction.

    IMO a better scheme - but not so glamorous - is to remove one cylinder and bore the other to 150cc.

    Four valve head, short stroke - and a plain bearing bottom end.

  4. #4
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    Sleeve the working cylinder down to 100 and yep, you'd be legal.
    Stock is best

  5. #5
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    Quote Originally Posted by Grumph View Post
    Hard to do well and it'd finish up pretty heavy with a lot of internal friction.

    IMO a better scheme - but not so glamorous - is to remove one cylinder and bore the other to 150cc.

    Four valve head, short stroke - and a plain bearing bottom end.
    Wouldn't going from a twin to single bugger up the engine balance? I'm in it for the glamor rather than the performance anyway
    "A shark on whiskey is mighty risky, but a shark on beer is a beer engineer" - Tad Ghostal

  6. #6
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    Quote Originally Posted by Henk View Post
    Sleeve the working cylinder down to 100 and yep, you'd be legal.
    And as far as fabricating parts, anything goes as long as it didn't start as a race part?
    "A shark on whiskey is mighty risky, but a shark on beer is a beer engineer" - Tad Ghostal

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    Quote Originally Posted by Grumph View Post
    Hard to do well and it'd finish up pretty heavy with a lot of internal friction.

    IMO a better scheme - but not so glamorous - is to remove one cylinder and bore the other to 150cc.

    Four valve head, short stroke - and a plain bearing bottom end.


    Where do you get a plain bearing short rod. Like for instance one that would fit into an FXR.

  8. #8
    Quote Originally Posted by Grumph View Post
    Hard to do well and it'd finish up pretty heavy with a lot of internal friction.

    IMO a better scheme - but not so glamorous - is to remove one cylinder and bore the other to 150cc.

    Four valve head, short stroke - and a plain bearing bottom end.
    I have one of those in the unfinished pile.

    Has been bored. New piston so is now 141cc. Balance weight on the crank of 91g made from 4140(just to mimic the rotating part of the missing conrod. Balance factor might still be on the piss). Has a blanking plate for the missing head. All tidy but the bore is a little tight I think.

    If anybody feels like making their lives incredibly difficult then make me an offer. Any offer considered.

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    Quote Originally Posted by Moooools View Post
    I have one of those in the unfinished pile.

    Has been bored. New piston so is now 141cc. Balance weight on the crank of 91g made from 4140(just to mimic the rotating part of the missing conrod. Balance factor might still be on the piss). Has a blanking plate for the missing head. All tidy but the bore is a little tight I think.

    If anybody feels like making their lives incredibly difficult then make me an offer. Any offer considered.
    Sounds like you are building your own mini Ducati SuperMono.

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    Quote Originally Posted by richban View Post
    Where do you get a plain bearing short rod. Like for instance one that would fit into an FXR.
    Off the cuff, Rich, early CBR600 Honda is within a MM or so of the right length. can't remember the s/e size sorry.

    If you want to find something trick, Bob Densem is importing rods with his own branding. Carillo replicas which look pretty good.
    Worth a ring to Denco to see if he's got anything the right length.

    That converted VT250 mentioned above would certainly be a good start point for someone. Balance will be close as is.

    Never yet met a bucket racer who wasn't in it for the glamour......and fame of course....

  11. #11
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    Sounds like competition parts. Apart from the CBR, that sounds real legal.
    Don't you look at my accountant.
    He's the only one I've got.

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    Quote Originally Posted by Grumph View Post
    Off the cuff, Rich, early CBR600 Honda is within a MM or so of the right length. can't remember the s/e size sorry.

    If you want to find something trick, Bob Densem is importing rods with his own branding. Carillo replicas which look pretty good.
    Worth a ring to Denco to see if he's got anything the right length.

    That converted VT250 mentioned above would certainly be a good start point for someone. Balance will be close as is.

    Never yet met a bucket racer who wasn't in it for the glamour......and fame of course....
    What about stroke length. Be awesome if one was lucky enough to simply give it a bore, and Chuck a CBR rod and slug straight in.

  13. #13
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    The concept worked great on this Ducati:

    http://thekneeslider.com/archives/20...le-conversion/

    Even has a pressurized tank under the seat that is charged when the bike decelerates to be used later for an extra boost!

  14. #14
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    Quote Originally Posted by Phantom Limb View Post
    The concept worked great on this Ducati:

    http://thekneeslider.com/archives/20...le-conversion/

    Even has a pressurized tank under the seat that is charged when the bike decelerates to be used later for an extra boost!
    Being three times the capacity of the 'bucket' version, it has something resembling torque to carry all the added weight.

  15. #15
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    Quote Originally Posted by F5 Dave View Post
    Sounds like competition parts. Apart from the CBR, that sounds real legal.
    You talking about the thread topic or the sidetrack?
    "A shark on whiskey is mighty risky, but a shark on beer is a beer engineer" - Tad Ghostal

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