Cooling fin question

[BCD]

I've noticed on some pics that some of you have what looks like strips of rubber between your fins. What's the purpose? I would think it would slow airflow around the fins and make the engine run hotter?

 

[Venice Motor Bikes]

The say the rubber blocks reduce engine noise. (& probably do.)
I also think they will slow the airfow. (I would rather live with the noise & a cooler engine.)

 

[eDJ]

One of the functions is to dampen vibration that can lead to cracks and chunks of fin breaking off. Motorcycle factories like Yamaha and Kawasaki have used plastic disc installed between the fins to help prevent that problem.

In some instances they "shot peen" areas to slow down the formation of surface cracks that can lead to such failures.

 

[Bikeguy Joe]

Noise dampening. I made some and it really quieted the engine...until they all vibrated out.