On a 16" alloy model, unbolt the engine from the chassis. you can then move the engine enough to get the belt on. Plastic bodied versions usually have enought clearance to do it without moving the engine.
On 18" versions, some have a support bearing at the outer end of the drve shaft. The official method is to drive out the roll pin fixing the pulley to the shaft extension, then proceed as for the 16" version. In practice, this may be rusted on, in which case unbolt the support bearing, move the engine as above, and slip the bely on over the bearing assembly.
phil_saunders(a)bigfoot.com
Phil Saunders, July 2009
