DT125R FORUM

Do you mean part number 17 on the picture and im pretty sure that's the crankcase breather.

yeah, they're road legal and Restricted but theres also a 200cc version. Pretty much Suzuki's competitor for the DT i think, doesn't seem like it sold too well though.

You also could have got one of these around that time.

They're fairly uncommon as well, have one in my garage in pretty poor condition.

This is exactly what mine did and it turned out to be the CDI but on the wires that recieved voltage it was a really low amount for less than a second to make it twitch, I was lucky and found one for £25 on ebay, you can also try searching for CDI from the Derbi GPR125 2T as im pretty sure its the same.

There's one in France for slightly cheaper than you have found.

http://www.ebay.co.uk/itm/DERBI-125-GPR-RACING-BOITIER-ALLUMAGE-CDI-2004-2008-/172221604252?hash=item281935219c:g:SmMAAOSwagdXSKlk

Got the nut off now, used
@MIGHTYMAN 's advice and put the engine back in the frame. Thanks guys