vfr750 big bore kit

Discussion in 'General VFR Discussions' started by grayband, May 7, 2008.

  1. grayband

    grayband New Member

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    Ok guys...I'v almost got the big bore kit done!!!! I'm picking up the resleeved cylinders this week for the big bore kit I've been developing for the 1994-97 vfr 750's. The final displacement will be 837cc and should increase horsepower across the entire rev range substantially! probably around 120 hp or so based on figures given by euro companies who do similar kits. The kit will include 4mm overbore pistons and custom sleeves with EVERYTHING made here in the USA!!!!! Probable retail cost will be about $1050 including the pistons, sleeves and hardware. And based on the dollar/euro conversion right now, this kit will cost euro guys substantially less then what they pay for a similar kit in europe of the UK. Let me know who is seriously interested so I can accomodate them on the first production run!
     
  2. v4pwr

    v4pwr New Member

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    sounds interesting. let us know the final figures. does the o.e. heads and valves work well with the larger dispacement, and do the carbs need to be rejetted?
     
  3. grayband

    grayband New Member

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    no head mods will be required.....the carbs will probably require no jetting changes other than a one size larger main jet
     
  4. Chris71Mach1

    Chris71Mach1 New Member

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    so grayband, what ever came of this project???
     
  5. douglasthecook

    douglasthecook New Member

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    Is this project still alive? It's been several years with no updates.
     
  6. Chris71Mach1

    Chris71Mach1 New Member

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    One thing I've found is that the 2nd gen VFR bikes can all be converted to an 840 (837cc) over bore motor. The 750s don't need anything more than a set of oversized pistons. The 700 bikes can be done too, but they need a crankshaft and connecting rods from a 750 motor first. From my research, I've found that the 840 pistons are 74mm pistons, which I've found is the size used in the old CBR929 bikes. The thing to look for is piston height and wristpin location relative to that of the stock vfr pistons. Past that, I think it's entirely possible to do this on the cheap without dropping a grand on a set of pistons.
     
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