/\ Like he said, the easiest and quickest solution will be to fit a new cylinder barrel. Whilst your at it, why not get a complete piston assembly, connecting rod, and a set of big end shells as a minimum. As all these items could have suffered damage which may not be visible to the naked eye. Also why not get a few other spares such as fuel pump, injector, and gasket set etc, even then it would still be cheaper than having your existing barrel reconditioned. As a final bonus you would then not always have that nagging doubt in the back of your mind if this repair would hold up.
As a final bonus you could then, always keep the gash cylinder barrel as a memento, to remind you of this incident
This tale of woe kind of reminds me of an episode back in my plant fitter days as follows:
At a location where temporary traffic lights were in use on a long term road widening scheme, the mobile plant fitter kept getting call outs in the middle of the night to replace defective traffic light sets, that kept having mysterious electrical faults such as all the bulbs blown, timer relays failing, etc.
The cause of these continual failures eventually became apparent, it was the after pub closing time sport for the local hooligan population to spray a can of ether into the air inlet of the running engine just to see how much it could take before the engine blew up. Those Petter AA1 engines sure were tough little engines [possibly because of the over square bore / stroke ratio], the problems were always electrical in nature due to the dramatic increase in engine speed and hence the increase in voltage above the normal 110v DC.
