But he said the PO didn't give him one. If he really can't get the original certificate, I'm sure a Yamaha dealer would confirm that the restrictor is fitted and sign the appropriate bit of paper for a small fee. The insurer will not be interested in whether the restrictor is fitted. What will matter to them is that you have TOLD them you have a restrictor fitted, so when you have your crash they will instruct the assessor to check whether it is STILL fitted. If it ain't, bye-bye insurance cover.

It's the same with other things they take on trust, like whether you park it in a garage or on the street, your medical history, and so on. It gives them something to check before a payout, and grounds to refuse if you have lied to them. It pays to be 100% honest with insurers.