What's the preferred method of carrying out the above as in what pre mix ratio, rev patterns and general break in procedure?

It's needs to be done on a Beta Rev 3 250 2007

Also how does the heat exchanger? Come out of the recess in the cylinder head?

running for a short time letting cool checking coolant level say 3 to 4 times then short steady rides allowing to cool inbetween again checking coolant also make sure fan works a little extra oil wont hurt but not much more then maybe a cuple of days steady riding and that should do i reckon

Oh and what do you mean by heat exchanger

http://www.lewisportusa.com/manuals/beta/Trials%20service%20manuals/2010-2011_evo2t.pdf

In the Evo manual they show what they call a heat exchanger which looks as though it sits up inside the inside of the head.

As I'm sure you know there isn't a manual for the Rev but it looks like its head has a removable hex as well and I would like to clean the carbon of off it and the crud in the water ways.

There's nothing with the new piston, re plated cylinder, my Beta's owners manual or the Evo manual about running it in, as it's all new And it's cost me a good few quid I want to make sure I do it right.

It is better to let the engine spin freely rather than lugging down to very low revs with high load.

Also varying the throttle position, accelerate/decelerate but this is the case with trials.

What you should not do is run in a continuous throttle position up hill and down dale.

This is the re plated cylinder done by langcourt, looks like new to me.

All you need to do with a 2T is seat the ring without overheating it

This happens in the first 20 minutes, do a couple or 3 heat cycles where you get it just up to operating temp with very light loads and cool for 10 min

Then ride it like you normally would but don't exceed 75% of full load, like I say, 20 - 30 min is plenty, then a few short hard pulls with a cool down and you are good to go

A hard break in is ok but you need to be careful you don't overheat the ring, the wrong thing is full load low rpm use like hill climbing