How much suspension play is reasonable?
 

My local garage is failing my 1989 3AJ's MOT on excessive play in the rear suspension. I changed the bushes in the monoshock linkage but they say the play is still too great. With the rear wheel off the ground they demonstrate this by pushing the swing arm up a few inches before it meets the resistance of the shock.

Are they right, in which case what is giving me the play now, or should I take it to another garage. Getting a bit frustrated now...

this is a common failure for trail bikes. its not that any one bush has excessive play but when you add a small amount of play in all the bushes together you get the large amount of play overall.

It may be that the bolts which run through the bushes are worn and this isnt helping matters.
with the bike off the ground try and see when a friend moves the wheel up and down where the play is. you should be able to see if its just coming from one bush or generally overall on all of them.
If youve replaces all the bushes i would guess its a worn bolt, remember to have the top shock mount checked aswell.
if youve done all this and pumped it full of grease then i would appeal to their better nature showing the receipts for the work youve done and explain its not any one joint but a little in all. they may buy this but its no guarentee, with an inch of travel in the swinging arm at the wheel theyre in their rights to fail it.

hope this helps