BMW R1200RT/R1250RT Forum

I threw an exhaust valve on my 2007 R1200RTP, totally destroyed the head and piston, only very minor nick in cylinder wall, near the top of the cylinder. Found a new head and piston on eBay and cleaned them up. Good tolerances, rings are tight, and I am ready to reassemble.
The Haynes manual states that pistons and cylinders are a matched set. So my question is how big of a deal is it to put a different piston in my existing cylinder?
Thanks in advance for your kind advice.
DR Walker

As per the Haynes manual, is the cylinder marked as tolerance Group A or Group B. Does the new piston match the tolerance specifications for the appropriate group.

There is also a "Piston-to-bore clearance" listed, if this is within spec., perhaps it's good to go.

If the "Ring end gap (installed)" is correct, this may be a good sign too.

The manual also suggests that, if the cylinder walls are scratched or scored, but still within the service limit, seek specialist advice on whether the cylinder should continue to be used.

[size=2px]As per the Haynes manual, is the cylinder marked as tolerance Group A or Group B.[/size]
[size=2px][/size]
[size=2px]The Cylinder is marked tolerance Group A. No marking is visible on the piston.[/size]

If the piston & rings meet the spec. for the Group A cylinder, then why not use it.