[How to de restrict a 1983 DT0125]

Can anybody tell me how to derestrict my 1100 mile DT 125?

thanks,

 

 

Nick

[1983 DT 125]

I have a 1983 DT125 with 1100 miles on it. I notice from the Haynes manual it needs 10 40 oil in the engine/gearbox. I have synthetic 10/40, will that be ok or does an old bike like this need mineral oil ? Be great if anyone can help with this.-Thanks, Nick