I have a Cotton 250cc Trials bike 1966 and the engine is currently undergoing a rebuild. It was a long time ago the Villiers 250cc 37A engine came out, but I remember there was a definite problem with removing the rear engine fixing bolt. So when it comes to re-installing, what is going to be the best way to get the engine in and feed the 65mm rear securing bolt into place without taking off an outer casing? Can it be done? Is there a special method, such as a hole in the casing to feed the bolt through or has the right hand cover got to come off before putting the engine back in place? Can anyone advise on best course of action as I would rather get engine back in all together.