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.
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.
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.
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.
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?
You are going to clean the sludge traps in the crankshafts? I’m sure you are, I just didn’t see you mention it…
Hi Simon. Thanks for the feedback and for following my journey with my Square Four restoration. Yes, one of the main reasons for pulling down the bottom end is to check and clear the sludge traps in the crankshafts. While I know enough about the bike’s history to know that it was well maintained (while it was on the road), it has been laid up for a good number of years so it is important to know that the oil paths are clear. A catastrophic engine failure due to a blocked oil gallery would be, well, catastrophic. From your own wonderful Amelia Squariel journey, you will understand that taking on a Square Four restoration takes considerable investment so it needs to be done right to ensure trouble free motoring in the years to come.
Really enjoyed the item. I owned a four pipe Ariel 4 in my youth and it was the only bike I owned that did not need to have the engine sprocket changed for sidecar work because of the torque. I fitted a Tilbrook sidecar to the bike and it performed amazingly well. However, the air passage between the front cylinders clogged up with dirt and muck, which I didn’t notice at that time, and one of the rear cylinders seized as a result of the increased heat. My mechanic replaced the S.U. carburettor with an Amal and that improved the performance.
Thank you Neville. Changing the carb and fitting a sidecar are two of the updates that I have in mind for later. I have a lot of work to do first before I get to that stage!
Hi Greg,
Could you please share some technical details on the crack shaft gear puller used on your you-tub channel. Eg thread diameter and pitch.
Many thanks,
Looking forward to the next video.
Cheers,
Rob
Hi Rob,
The puller thread, I THINK, is 1 11/16″ x 20 UN. The caveat here is that I have fitted the gear cover to the engine already so I am measuring the internal thread on the puller and best guess to the OD of the thread. It might be 1 3/4″ but I don’t think so as that looks too large and the TPI does not line up on the threading chart. I have checked the TPI with a thread gauge and 20 is correct. Draganfly sell the pullers for around GBP30 as an option although making your own is usually more rewarding! I may be taking the case off again soon so I will check for sure if and when I do.
Regards,
Greg
Any idea where std bigend shells can be obtained Dragonfly out of stock currently Cheers Tim
I have done a lot of waiting for Draganfly backorders! Maybe try contacting Bennet at Iron Horse Spares. He may know of somewhere else to get them.