Dismantling the Bottom End

Last time was about the top end. Dismantling the bottom end is next. Good news is that I have made videos of this on my YouTube Channel for your viewing pleasure.

Dismantling the Square Four bottom end down was straight forward enough. The main challenge was the coupling gears that connect the two crankshafts together. There is a special puller that is required to remove these gears. I have one that a good friend made for me many years ago. It was good to know that it was still in good working order after all these years.  Removing the rear coupling gear gave me some cause to ponder. If you have seen my video on dismantling the bottom end, you will see that my first video stopped here.

Ariel gear tool

Square Four Coupling Gear Puller

I have a copy of a workshop manual courtesy of Drags. I have not had to use it too often. However, when I have used it, it has been invaluable. Once again, I was able to work out what I needed. There is an oil seal on the rear gear. In this case, the seal hard hardened to almost a metallic state. No longer useful for sealing oil, once removed, I was able to remove the rear coupling gear.

4GMK2 Crankshaft gears

Square Four Coupling Gear

Splitting the Cases

For such a large and complex engine design, the business end is surprisingly simple. Two crankshafts are coupled together. Two 500cc twins become one 1000cc four. Thank you Edward Turner! Removing the remaining bolts holding the crank cases together, a couple of taps with a soft hammer and apart it came.

Ariel 4G pistons

Four Cylinders Ariel Square Four

Damage Report

I have mentioned in a previous post that there is visible wear on the camshaft. No surprises then that there was visible wear on the camshaft! These are available on an exchange basis from Drags so I will get that sent off soon.

The bottom end is in pretty good shape. There is no visible scoring on the big end journals. There is wear on the bearing shells which is expected. Again, no scoring or bad marks on the shells. The big ends journals have been previous ground and are 0.20” under size. The pistons are standard bore and look in good condition.

4GMKII Ariel Crankshaft

Ariel Square Four Crankshafts

Next Steps

What next? Heaps! I have started cleaning the parts and sorting the parts into their correct order ahead of reassembly. Piston rings, bearings, bushes and seals need to be ordered. The camshaft will need to be reconditioned. The cases will need to be cleaned and polished. Valves and valve seats need to be ground, and the broken cooling fins need to be repaired. Anybody want to buy a kidney?