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Rebuild a 250 Alpina 1974 type 115


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  • 2 weeks later...

Piston : Help ...

I have no arrow in the top, A or B in the exhaust side ?

I will put the "B" with the holes probably for the lub oil ...😒

To reduce the costs, I will keep the piston (the cylinder has no scratches and is very clean)







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Your Alpina project is coming along nicely!

As long as your old piston, rings and cylinder aren't too worn, there's no reason to replace.  Check the end gap on your rings when seated in the bore and compare to the tolerance measurements to the specs that can be found in the manual.  Same with the piston. Measure the width of the bore and piston to determine if it's within spec. and, if so, just clean up your piston and run with it.  As may have been mentioned earlier, a new piston pin and bearing would be advisable.

As to orientation... the piston ring locating pins (in each ring groove) face toward the intake (carb) side of the cylinder. 

You're doing great - almost there!  Looking forward to hearing about and seeing your final results.

Good luck!


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In the box 😄.

Engine is now closed, as I will move soon to Delaware I will have no time the next month for it. 

I have to:

- Install the engine in frame,

- Ignition and electrical circuit to manage.

- All cables, 

- Exhaust to do : I have some parts but still work to have the line finish,

I will be back, thanks for the supports 😉,,,,


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  • 2 months later...
  • 2 weeks later...
  • 2 weeks later...

Would be easier to fit connecting link at rear sprocket.....is the chain in two (or more) pieces ?

What's happened to chain on lower run beneath brake arm bracket  (bottom r/h. corner of pic) ?

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So you did not change anything (You haven't mounted a bigger front or rear sprocket)? 

Then probably the position of the wheelaxle has changed.

Last not least all my Bultacos needed and need a half link to have tbe proper chain length?.

May be that is missing right now? 

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