NSR250 MC21 Flywheel

[Cru Jones]

The MC21 flywheel is < half the weight of the RVF400's and seem to be readily available, so was wondering if anyone has ever tried to swap an MC21 onto an RVF400.

[RoninZX-10R]

I haven't tried a flywheel from an MC21 but I did install a GSXR flywheel on my RVF400 racebike which really helped improve things by reducing the rotating weight on the heavy crank. I've since gone to total loss, so no flywheel or stator, which made a huge difference. It's harder to launch off the start line since the flywheel weight helps with ertia on the crank. I have to really concentrate when launching as it's easier for the revs to drop quickly. Also, the reduced weight on the crank will increase engine braking which makes things challenging on bike without slipper clutches, but for us it's great.

Is the flywheel from the MC21 the exact same shape as that of the VFR and RFV400?

[Cru Jones]

The shape and dimensions look very similar, so would need someone like TygaPaul who has access to both to verify. If it works then would be a lot cheaper than going the RO and GSXR route.

[Drunkn Munky]

I got a mc21 motor im about to strip, could check it against an rvf one when i get it off. If im honest though im sure this route would have been explored before going to all the hassle of producing a kit for the gsxr

[Cru Jones]

I got a mc21 motor im about to strip, could check it against an rvf one when i get it off. If im honest though im sure this route would have been explored before going to all the hassle of producing a kit for the gsxr

Yeah, that was my only hesitation about this theory as well.

[Cru Jones]

So a bit of investigating has determined that the stator dimensions between the MC21 and NC35 are similar, but not the same.

• NSR250
  Outer Diameter: 102mm
  Inner Diameter: 42mm
  Thickness through hole: 14mm
  
  
  RVF400
  Outer Diameter: 107mm
  Inner Diameter: 42mm
  Thickness through hole: 15mm

So...maybe you could install an MC21 stator and flyhweel onto the NC35, but then I'd be concerned about the MC21 outputting the same voltage...

The reason I even bring this up is that you find MC21 flywheel & stators in Japan for well below $100 if you try and that's substantially cheaper than the Rick O gen cover and GSXR setup.

[Harryredchow]

Surely the flywheel will be specific to the ignition timing. Is the angle of the 2 stroke V twin the same as the V4? The pickups would also be 5mm further away and probably need modification.

Seems like more trouble than it's worth.

[Cru Jones]

Surely the flywheel will be specific to the ignition timing. Is the angle of the 2 stroke V twin the same as the V4? The pickups would also be 5mm further away and probably need modification.

Seems like more trouble than it's worth.

Isn't the RVF's ignition pickup on the clutch side? If so, then ignition pickup wouldn't be an issue.

[hunter]

Surely the flywheel will be specific to the ignition timing. Is the angle of the 2 stroke V twin the same as the V4? The pickups would also be 5mm further away and probably need modification.

Seems like more trouble than it's worth.

Isn't the RVF's ignition pickup on the clutch side? If so, then ignition pickup wouldn't be an issue.

Yep other side.

[Neosophist]

i seem to remmeber the generator being interchangable betwen one of the nsr250s and the rvf / vfr?

having had a quick look on electrexworld they list the same replacement genny for nsr and rvf / vfr.