1965? R27 piston position.

[Old Bob UK]

on rebuilding the engine of this R27, (the owner had partly stripped prior to removing
from bike for investigation of 'bearing noise'; I noticed the piston just doesn't look right.
At TDC it is app 7mm short of the top of the bore. The top ring mark in the bore is app
12mm down. The owner says he had no concerns as to performance or compression feel.
Am I looking at a problem that isn't there???

Markings on piston crown :-
   W23D  or 1123D
    SP 0.05
   90082
   69.95
Please verify if there is a problem.
Regards Bob.

   

[Old Bob UK]

[Dappsull]

This is how it looks on my engine at TDC:

https://www.flickr.com/photos/dapsul/3562732602/

[Old Bob UK]

thanks Dappsull,
                          yours  'looks' higher up the bore than mine.
Would it be possible for you to measure,approx, the depth from the top
edge of the bore to the top edge of piston? Also, with a straightedge
horizontally over the piston crown down to the bore edge. mine only reads 2-3mm.
Sorry I seem to be having trouble posting pics.
Hope you can help.
                           Bob.
.

[mekgyver]

Hi Bob,
may be, there is a wrong conrod build in, or a wrong piston-height, or a wrong cylinder-height.
You have to measure alle those parts.

I had a look in our comparisontable : Vergleichsliste

The easiest fault is , a R26-piston is build in. The difference with the height to a R27 piston  is about 5mm.

Regards, mek 

[Beemer]

Hei Bob, I faced the same situation at my R27. The piston was approx. 10 mm to short. The piston was no original.
So I installed a new piston with perfect sizes after having the cylinder bore drilled suitable for the diameter of the
new piston. Al sizes of the piston can be seen from this forum.

Best regards from

Kurt (Beemer)

[Old Bob UK]

Many thanks to all who replied and confirmed my thoughts.
Now I just have to convince the owner, but at least I have
something to show him.
Thanks again Bob.