Thats quite amazing piece of work..
My only experience with Arrow engines was when invited by Pat Wise to the Thruxton 500 she was riding partnered by Olga Kevlos ant partway through the race bike wasn't doing to badly but came into the pits with the engine Knockin the heads were removed and found the pistons hitting the heads so a surform was used to file the pistons down it was reckoned the rods were stretching this happened twice they then retired
Never found out if that was right or the pistons..