I purchased my MC21 in Nov last year.The seller told me it had had a recent top end rebuild.He had no paperwork to prove this though.I took his word,(I wanted the bike),and he was proved a liar.
The crankcase oil seal failed and the engine needed stripped.I used a local dealer who I have known personally for many years.When the engine was stripped down it was then obvious that the heads hadn't been removed for some time and the pistons were approaching their last legs.I got this done then and there,the old parts shown to me and a receipt given.
The lesson is-DON'T TRUST A SELLER! Ask for proof.If he cant give it to you,why not?I am new to 2 strokes too-I am learning slowly but surely.
Craig