Where do you draw the line? 5 years and 25,000miles and he should pay? When does the obligation from BMW stop?
Actually in UK Consumer Law and the Sales of Goods Act. Its 6 Years (5 years in Scotland I think?)
Then their legal obligations stop.
Items you purchase have to be 'fit for purpose' and last a reasonable time before they break (cost of item is relevant to this). In Law the maximum time is 6 years to make a claim.
A Judge in Court will decide if you have a reasonable case for compensation, based on the value of the item, it's use and any other relevant points.
You may not get a full replacement at no cost, but you should get something back... It may be less than what the Manufacturer would have given you in an 'out of court' settlement.
Depends how reasonable you are, and how reasonable the other party is to negotiate a fair solution.
Also, if you purchased any part of the product with a Credit Card (over the value of £100), the Credit Card company is equally liable under the Sales of Goods Act and can be approached to either assist you recover your costs, or you can make a claim directly against them. Section 75.
Sometimes if the original company who sold you the goods has gone bust, the Credit Card Company can be dealt with on the item.
Also, if you purchase a brand new motorcycle, most manufacturers and their dealers are members of the Motorcycle Industry Association.
http://www.mcia.co.uk/
They have a 'Buy with Confidence' Code of Practice and provide an arbitration service if things go wrong, which results are legally binding.
"Membership of the Association for a manufacturer or importer of motorcycles carries with it a commitment to act in accordance with a Code of Practice, which sets standards to ensure that all motorcycles, scooters and mopeds are supplied in a safe and responsible manner,
that they fully meet the expectations set in promotional material and that after sales obligations are honoured. The Code also provides an independent escalation process, through an impartial Chartered Trading Standards Institute (CTSI) certified Alternative Dispute Resolution (ADR) provider*, in the unlikely event that a problem occurs and a customer is dissatisfied with the outcome of a complaint."