Air head rocker-arm bearings
Just checking the valve clearances on my R100GSPD, and found a needle bearing roller lying in the valve cover. On removing the rocker arms, I found that the bottom cage of one of the rocker arm bearings had broken/worn away, allowing the needles to drop down through the slot in the mounting block, into the engine via the push rod tunnels. Removing the sump found three more needles. All are now removed and the offending bearing remains have been replaced.
This is not the first time I have come accross this on various air heads.
Does anyone know why this happens, or if there is a way to stop it happening again?