Royal enfield interceptor 650 valve clearances

Just started my annual service of my interceptor. Easy job, which will be even easier next time as it was all new to me today and I was following Stuart Fillingham on you tube! It's an easy job, I had to go to Halfords as I assumed my feeler gauges were fine, but I didn't have the correct sizes. I can thoroughly recommend the halfords ones, as they have the correct sizes! The valves were very close to the specifications, I doubt if I've actually altered them. I did find several initially felt tight, but then they

were good. Is this due to a film of oil on the rocker arm? It seems if you put the feeler in from the side it felt the gap was correct but going in from the tip of the feeler it felt tight. Anyone else found this?
Doing the valve clearances brought back ancient memories from the 1970s and 80s, servicing my old Morris 1000s and mk1, 2 escorts!
Renewed the air filter, which looked like new at 5k miles and was dated 12/2018, so probably the original.
Renewed the spark plugs, the gaps of the old ones were fine.
Next on the list is to do an oil and filter change and remove and clean the callipers. Be ready for spring then!