when i bought the bike the lad said it had a performance derestricter type box,after s bit googling i spied a thread that said the splutter the OP had was down to this box

quistion is,where the hell would it be if i have one?

Usually located at rear of speedo and plugs into connector that normally plugs into speedo connector.

By "splutter" do you mean misfire and no rev above 5000 rpm.

between 5-7k it coughs n farts and has no go then it picks up and used to pull strong till redline,now every now n then its bogs down for a second at around 10k

I take it that the bike ran well in the past, when did problem start.

De-restriction box usually refers to unit used to foll the ignition control unit that the speed sensor unit in the speedo is functional ie will get in at 180kph. If de-restriction box fault would not expect engine to ran above 5000 rpm, therefore would not get to 5-7k.

Sounds more like carby problem, blocked jets, bad fuel or water in float bowls.

magg wrote:Usually located at rear of speedo and plugs into connector that normally plugs into speedo connector.

No always. There are also derestrictor boxes that plug inline with the CDI and the loom.

As for the dip between 5-7000rpm, this is a normal NC30 trait. There are many ways to reduce this and a good look through previous threads will throw up different suggestions to reduce (or eliminate it)

The easiest way to get rid of it is with a programmable CDI and advance the ignition in the area's needed.

Is this problem the continuation of the one from your other post about missing clamps, airbox snorkel, flap and moded stacks or something new.