"LX250" sounds like the KLX engine No!!
I had a KX 420 back in the day that I restamped* with my KLX engine No. so I could ride enduro's on it.
Pretty sure I restamped it back with the original 420 No. before I sold it though.
I remember going through scrutineering at the Wonthaggi 6 hour in I think 82.
They were trying to crack down on dodgy rego's that people were trying on to get MX bikes into the event. The scrutineer looked at me wheeling in the 420 and started smirking, "has this got real rego" he asked. Sure I said. He asked for the rego papers and started checking the engine No. LX250#####
Oh. This ones fair dinkum he said surprised.
I was surprised he didn't pick up the it was LX250### instead of something like KX420###
* Can you be held acountable for such things now that more than 7 years has passed
Anyway, Vicroads shouldn't beleive anything they might read on the net.