Frame sliders/engine guards

[Bazbro_imp]

Can you weld that broken mount ?

Yes, I could, John.
The best course would be to...
1. Take the engine out of the frame and replace the lower engine block. Or
2. Next would be an engine-out, strip-down alloy-weld repair. Or
3. Then an in situ alloy-weld repair, and finally
4. A JBWeld repair.
Removing the engine is out of the question - it would ALL have to be done at a dealer and the cost would be prohibitive! It ain't gonna happen, 'cos I can't do it myself.
I spoke to my welder (who coincidentally owns an old Honda Four!) and whilst he was prepared to look at the job and maybe have a go, he was unsure about doing it in situ because of the heat generated by the weld
. At that time I was going to take the 'bike for him to have a look, on my way bringing the 'bike home. My 'trailer plan' failed when the hitch broke so the 'bike was brought straight home here and the welder hasn't looked at it yet.
I decided to at least TRY the JBWeld - I'll be keeping a VERY close eye on it. If the product is as good as the reports, it'll be fine. If it's not, I will have to deal with it then.
The crack itself is UNDER the weight-supporting part of the bracket. It is totally supported on either side by big penny washers, clamped and torqued up, then clamped to the frame. The weight is downwards, onto the unbroken part and I can only see it breaking again if it gets an upward whack like last time. Of course, it may fail through vibration, heat, whatever but all reports suggest that will not be the case. No weight is being taken by the weld - just holding the loose underneath part UP onto the solid top part.
It is what it is and although not ideal, I'm keeping my fingers crossed. (And toes, and arms, and eyes!).

Please don't think I'm a naysayer, but isn't engine torque going to pull the front of the motor up?

Please don't think I'm a naysayer, but isn't engine torque going to pull the front of the motor up?
Yes, and there will be all sorts of other minor stresses too, in all directions. But the major stress, the sheer weight and bulk of the engine, is downwards. The engine torque also has to fight against that not-inconsiderable weight and it's also lessened/softened by the movement of the 'bike itself.

Thanks for your thoughts, Dover. We shall see how the joint stands up over time. It will certainly be checked before, during and after every ride!