Being that the engine is only 3mo old Hobby Services should repair it out of good will even if they will be out of maybe $25.00 in parts and shipping.

When you think of it that $25.00 will likely bring them a repeat customer but a few more posts like the op made and it will start to cause them to loose
sales I know OS makes nice engines I have some myself but if they to get strict on their warranty service I dont think it will good for them in the
long run.