smc st1300

Hi guys after rebuilding my secondary master cylinder and caliper I have replaced both boot bushes on the caliper but for the life of me I can't get the bigger boot bush back in is there a technique to it or a special tool plz because I'm loosing all patience with it now many thanks for any help item 13 pic

Thought I recently read where the bush has to be inserted from the rear side. With the end (designated by the number 13 pointer, in photo) going in the hole first...

Lol cheers it's a fiddly lil thing