I'm in the process of building up a road bike from my rather oversized spares collection, the engine I'm using has a problem with one of the exhaust stud holes for the front downpipes (namely that it's knackered), so I've taken off the front head and I plan to just swap over to one my spare heads,

So yesterday I took off the old head and noticed that there's a fair bit of carbon build up on the cylinder crown, and also on the bottoms of the valves on my spare head, what's the best way to get rid of this? guessing it's not a good idea to use any abrasive so need a decent cleaning fluid of some kind?

Also, whilst I was having a look around I noticed some casting marks on the inlets and exhaust bits, is it worth taking a dremel to these to smooth it slightly?

I also plan to remove the queitening gears as well, but are there any other quick/simple/'free' mods that can be done whilst I'm there to vaquely gain more power? (I'm under no delusions that I'll have some 80bhp monster, but every little helps and all that :p)

Have a look in your local directory and see if there is an engine reconditioner near you that does Soda blasting.Not bead or anything else.Its well worth the bother as it is non abbrasive and can be washed out with warm water.Leaves the parts like brand new.

Sounds good, I'll have a look for somewhere that does it now.

Will soda blasting require me to dismantle the engine further or will they be able to do the pistons still in place in the block, and the valves whilst still installed in the head?

Best to strip it out as far as you can.Its not like bead blasting,it doesnt change the surface,just completley cleans it.And wont wreck the engine if you get a speck of it in the oil system.Its non abrasive,and if you wash the parts in hot water after you are safe.

Removing carbon deposits, if you have a wire wheel just run the valves over using that works a treat and to be fair very slightly with some wet and dry i took most of the carbon from piston crowns, anyhow remeber to seat the vavles back in good m8 !