I had the misfortune of very badly damaging my longstroke engine earlier this year (collapsed mains i think + three holes and a radial split in the right hand crank chamber). I am working out what bits i can salvage before seeking help on rebuilding it but since these things take time I am considering putting the engine from my Brum project into the bike so that i can at least keep one of the machines on the road.
My earlier machine (with damaged engine) is a single downtube, RZ long stroke blind head engine and 2 inch LH exhaust – it looks as though the Brum engine will go straight in, perhaps with the exception of needing to fit a shorter set of carburettor mounting studs to prevent fouling of the carb on the downtube. Obviously i’ll need to put the generator and distributor/pilgrim safely to one side (the early bike doesn’t have lights) and run the ignition from the existing clutch driven magneto and oilfeed from the gravity drippers. Before i get stuck in i was wondering if anyone has done this and found any other things to watch out for – at first sight it looks like a straightforward job but i’ve found with Scotts that things look straightforward until i try them ?!
You will need to check the engine mounting holes to see if they will line up ok. I have come across a variation of over an 1/8″. This can be overcome by making up some eccentric bushes and using a smaller diameter engine bolt. By doing this, you can return everything back to standard at a later date.