Does Anyone Know?

[Keith Phillips]

Here's a couple of brain games for the classic guys. Why has the Meriden 750 Bonnevilles got holes drilled in the cooling fins either side of the head?

I have asked a lot of classic riders within the clubs around NZ but know one really knows the answer. Maybe some one her can tell me.

I also see the 750 barrels have one fin less than the 650 Trumpets as apparantly with 8 fins the 750 motors were to high to fit in the frames. So I have been told. Is this correct?
Thanks in advance
Keith

 

[gumpt1oo]

My T140 has holes in the fins. My understanding is the holes had a hard rubber material pressed through all the holes to prevent vibration noise through the fins, Mine still has the rubber in the holes, it is very hard and brittle now though.

 

[shanered6]

You are right Steve that's exactly what there for , it's done on a lot of old air cooled bikes and it is for fin rattle !
But over time the rubber goes hard breaks out and never gets replaced .

 

[Keith Phillips]

That's cool guys I can now tell my mates what the holes are designed to do. Just curious my Bonne has just the holes now no compound in the holes at all. It doesn't have fin rattle though, I wonder what it sounds like has anyone heard the fins rattle on an old Brit bike?

 

[Rocky]

I did not know this.
It's amazing the things I learn every day

 

[Keith Phillips]

Good on you Rocky. I guess it's the old addage where as a day you don't learn somthing is a day wasted.

 

[Rocky]

Good on you Rocky. I guess it's the old addage where as a day you don't learn somthing is a day wasted.

 

[grandpaul]

On the 750 cylinder height, the first 750s were actually just slightly longer stroke 650s, something like 728cc, till they bored them out even bigger (still not 750, only 749cc). So, the added height of the engine was the longer stroke. This results in mix-ups when ordering "750" pistons & rings.

 

[CarlS]

I learned something here. I did not know what the holes were for. Thanks for the info.