I think it's the oil, I believe the general oil change at 7500miles is way too high.
I do mine at every 4k. although it's not good, cause I know I lost the factory warranty, but better to have the bike(engine) longer than 4 years isn't it?
Car oil change is (was) used to be at every 10k. or 6k.miles, but the factories changed those too to way higher. If you think about it you will realise it's good for them, but not for us.
I'm sure you want your bike engine to live more than 4 years, well they don't really. Just take a look the Japan factory move to Malaysia. Also Yamaha made in China. They would love that if we would buy every 3 year a new bike, but who can afford that?
Anyway try to change the oil. I think the valves make the ticking sound.
You could get Castrol motorbike oil from ASDA, cost £10 each. You need 3 bottle and about 2.5 Liters can take the engine when oil replaced and not dry. Also change the filter, cost £8, it's worth it when you change the oil.