I'm really hoping someone here can drop me a hint on the right direction or the correct tool or technique for undoing the lockring holding the chainring/front sprocket to the crank on an old fashioned BMX style chainring.
The bike is a 20" child's mountain bike (Giant Animator, 10+ years old, I would think), but hours of googling suggests to me that it is partly based on older BMXs - hence choosing to post here where I bet there are people with long memories and substantial expertise!
Original issue: Bent chainring / front sprocket - needs replacing. Progress to date: Square taper cranks removed using appropriate tool. New 40 tooth sprocket with chainguard sourced - this is BMX old stock, and looks identical to the one being replaced (except for cosmetic details of the guard) - single circular central hole, no "spider". Problem: Chainring appears to be secured to the right crank with a lockring - this is about 25mm (1") diameter with about 16 "teeth", but is very thin. I cannot undo this.
So far I have tried pump pliers (are these known in the USA as channel locks?), and a hammer and screwdriver, both of which I have seen suggested by searching, but neither of which has worked. I have also tried a bike hand YF-157 lockring tool, but it can't grip something so thin.
Anyone got any advice on what I need to buy or do? Do I need a small sized "C-Spanner" - something like this https://www.cromwell.co.uk/KEN5805250K , or is there a cheaper or better solution?
All advice gratefully received as I'm a bit stuck - I suspect I'm missing the right terms in my googling... If you need any more information (e.g. accurate measurements) in order to help, just ask!
Thanks to anyone who took the time to read this, whether you can help or not!