ebay buyer problems

[grovehead]

hi guys im having problems with a buyer off ebay , basiclly i sold him a os 30 vg engine 3 WEEKS ago and hes just sent me a message saying its low on compresstion but hes not tried to run it as he dont think it will run anyway . before i listed it on ebay i put a brand new conrod in it and it had plenty of compresstion .

i know hes trying to have me off here but what can i do about it as i know ebay always side with the buyer , i cant understand why hes only got in contact after 3 weeks i think hes ran it lean and over heated it and nackered it up ..

how can i prove this as he says he will start a claim agaist me if i dont refund him ...

any advice would be great as i dont know what the best thing to do is