oldmxer, the largest of the RM tanks is the RM250/400N as LWC said at 8.5 litres. A full tank on the 400C used to give me near an hour of open fire trail type riding. In the scrub a lot better is acheived but when it's constantly on the main it ripped through the fuel. A 175 would not be so thirsty
and you wouldn't be riding absolutely flat out for the entire hour so I'd reckon, yes, you would get an hour and quite possibly more from the 8.5 litres on a PE175. Why not whack in a litre or even half a litre and see how long it lasts, this would give you a fair indication of what to expect and it would probably fall into the higher useage because during a short burst of 10 to 15 minutes you can ride harder than during an event of say 1 hour duration.
