Last year I added a "Ramair" foam sock filter over the Inter bell mouth. Seemed innocuous enough and on the road I didn't notice any adverse effect so, although it's ugly, it should help keep the engine wear rate down.
Today I took the bike out just locally, but it kept bogging down on wide throttle. Home again and removed the sock and the inside is getting blocked as if with with black glue. Possibly castor oil spit back? Big single with more than average valve overlap. Anyway...removed filter and performance fully restored.
I might soak a bit of the foam in E10. But anyway...if anyone else uses these things, I'd be interested to hear of experiences.
And if anyone does have one, I suggest you take it off and turn it inside out to check it.
ugly
Your not joking it's ugly, looks like it needs darning.
Have some of them
Have one on my Comet. Also one on the B40 as I had to move the battery to where the original air filter was. In order to adjust idle without removing the battery. The road racer Honda has two, no difference in air fuel ratio. It needed air filters because my enduro riding son has a curious habit of leaving the asphalt track and going in the gravel traps. Have not experienced any problem. All these bikes goes on ethanol free petrol.
Sometimes extending the inlet length (long trumpet, filter?) changes the harmonics and mucks up the breathing , I get similar blowback on my overtuned 250. Going to try a nice short curved bellmouth .