FE and F2 Mazda engines are clearance engines. My suggestion is to also change the water pump, cam and crank seals while you're in there.
Yes, Swoop is right, i have over 80 of XM´s and i never got a valve damage. It´s a safe engine definetly ! But it could happen...
yes the Mazda UA and F2 series engines were as you call it "safe engines". The valve clearances were fairly wide so the chance of valve damage was small, not non-existent though, if the belt was to break if the engine was at high rpm's valve damage can occur. Most of the time it doesn't because the belt usually breaks during start-up.
hopefully you checked the idler tension pulley also and replaced that if need be, they can cause this to happen if they lock up from bad bearings.
Hi claxby yes the Mazda M420G engine fitted in the Hyster XM range in the 90,s is a safe engine i worked on Hysters for over 20 years and we had quite a few cambelts snap and never had a problem with the valves or head just fit a new cambelt turn the key and everything will be ok its an easy change on these engines as well