Hello Dan,
I am using the RST 191 Suspension forks too with the same type motor you are using. the "600w" BL motor from WE. I chose the forks because they are made totally of CrMo steel and have some simple spring suspension. The drop outs are 6mm thick STEEL in capitals for those that might still think they are an aluminium or magnesium alloy. (check his pics again, that is nice tig welding holding it together) not a mag casting or alum weld job on these cheapies. Steel axle to CrMo fork is why you have 700 trouble free miles so far. The first forks I tried were T6 alloy and cracked quickly.
These cheap forks have a reputation for binding up easily and squeaking a lot as well, turn the bike up side down, undo the screw in the bottom of each fork completely, pull the forks off their shafts and apply a good dose of light GP marine grease, Vaseline or fork butter to all the sliding bits and seals and reassemble. Did it four years ago with the marine grease when I first noticed they might be dry, haven't done it again yet, tooo easy.
The motor axle on my hub (WE) had to be filed away a lot to accommodate the drop out shape ( I used a 5" angle grinder with a 1mm cut off wheel, that's a scalpel in my hands). The drop out wasn't nearly deep enough to centralise the axle in the lawyer lips for instance, also the long tang that stops the torque rotation was only 2.8 mm long along the axle and the drop out is 6mm thick, solution, grind the tang back along the large diameter of the axle so it has full 6mm engagement. That is the single mod I would most recommend when using forks that have a nice thick drop out.
I am not intending to add torque reinforcement until I have dial calliper evidence the drop outs are spreading. IF the drop outs do spread, I will probably weld a 6mm internal diameter by ~2mm wall thickness tube ~28mm long across the end of the offending drop out, then cut the tube to re-instate the axle slot. Once the axle is back in place, a 6mm Hi Tensile cap screw through the tube will stop it from spreading, provide clamping pressure if possible to the axle, and stop the hub motor from dropping out. If it is necessary and works as well as intended, I might do it to both sides.
The nuts that came with the motor were a typical mass production chee-po sloppy fit and there has been some discussion here they strip easily, I scrounged some Hi Tensile nuts the right thread from under a Nissan at the car wreckers, looks like they are used on the front suspension mounts. These nuts are a much better fit on the thread and even have a nice HI Tensile washer built into them. I can torque these up past the recommended 35Nm without any fear of stripping the threads. However, that washer does not fit into the "lawyers lips" on the drop out so I found some smaller OD washers and used those to fill the gap. I actually quite like the safety aspect of the lawyers lips, so next step is to get some car wheel nuts the right thread and spin them in the lathe if necessary to make one side fit into the lip recess nicely.
So far I have no intention of fitting torque arms where the engagement is so good and its good steel on good steel.
Battery pack is also going from 36v to 48v as I like the extra rpm too, Not going any further as more speed might attract blowflies. I have a 16 amp 240v domestic power circuit breaker in series as a battery isolator and so far it hasn't tripped in operation although if it does, I can fit a 20 amp and so on. The WE HD regen controller is "supposed" to be able to handle 50 amps 72v, I doubt 50A is a continuous rating and I think the caps may only be 63v, another reason to stop at 48v.
Alan
