Bultaco Questions

[southnztim]

I see for a Mk12 that the piston had windows in them (From what I can make out). Did this occur in all models with the introduction of the reeds? Is it an improvement or would a normal piston do. Any information would be helpful.
Thanks, Tim

[Moto]

Hi Tim,
        For the reeds to work ,you need to have the windows in the piston.Its a normal piston with the addition of the windows.

[southnztim]

Thanks Moto. Do you know the measurements by any chance. I have a piston with the windows, but it looks quite a bit different from a photo of a stock one

[sleepy]

Is it a 250? I think I have an old piston for one somewhere that I could measure.

[southnztim]

No, it's a 370. Thanks for the offer though

[jimg1au]

sleepy
could you take the measurements for me pls
I have a reed 250 motor coming

[sleepy]

sleepy
could you take the measurements for me pls
I have a reed 250 motor coming

Strange piston for a Bul.  As best I can measure.
   
  Dia- 70mm stock
  lenght- 67.5mm(not including the dome)
  dome- 4.5mm
  comp height- 31mm
  pin dia- 20mm
  ring pegs- 30mm either side of center on front
  windows- 2 of 17mm wide, 4.8mm bridge, 29mm high at bridge and 24mm high on the sides. 14.8mm from
  the bottom. All straight edges with about a 4mm radius in the corners.

Hope that helps.
The piston I have measured is a Wiseco but it looks correct for the inlet port.

[SON]

If its a Wiseco it should have some model numbers on it

[sleepy]

If its a Wiseco it should have some model numbers on it

It only has the oversize marking on top which is all they early Wisuco's did. It has 415 on the pin boss which according to an old cataldog should be a Bultaco 250 Astro 77 - 79.

[jimg1au]

thanks for the info