how about this? split the casese, drill it out to let say 14-15mm, get a suitable sleeve made with 1mm thick flange, press it in, you can just slip fit it in using loctite bearing retaining glue if you can not get it made to tight fit, check everithing before puting it back together, replace bearings if necessary,fit new seals and gaskets and there you go. now you have a motor that works as it should. why are you soo unwilling to split the cases? it isnt that hard.