Fin dampers

[relic]

Any reason why you shouldn't use some rubber fin dampers on the cylinder head?
I'd like to try some as my B+ has an annoying harmonic wail at around 5200-5300 rpm which is about 40mph in 5th gear. I don't see any in the parts book and I have no idea if they will help but I can cut some up out of old rubber and try them. (Unless there is a reason why I shouldn't)
Ken

[Bill2001]

On older BMW boxer twins we would add the fin dampers by using 1/4" fuel hose cut just a tad thicker than the fin spacing. I have no idea how effective they are on a Hodie.

[relic]

My Yamaha DT400 is supposed to have them...long gone with no issues. I don't recall them on my R75/5 but I have seen them on Beemers from the 80's. The hose idea is a good one, thanks Bill.
I can't see how it would hurt? I was just concerned if there was some odd reason for not using them on the Ace, I don't want to break a fin. Nothing to lose; I'll try some.

thanks, Ken

[robert campbell]

Not sure if they will fit, but the were stock stuff on the Yamaha 500 singles in the mid to late 70's. They were solid rubber about 1/2 in diameter and around the same width you are talking about.

Part number 9 in the below diagram

http://www.yamahapartshouse.com/oempart ... b/cylinder

[Hydraulic Jack]

The dampers hurt nothing. Not used on Ace, very likely, because there was no perceived need. The fins on the Ace are shorter all around compared to the later alumiferric style. Shorter fins vibrate less or at least don't transmit high frequency as well. They will not remove dingle from the engine. All they are likely to do is reduce a bit of noise. Try some and see, just don't go overboard and block air flow.

My guess is the wail you hear isn't coming from the head or cylinder fins. You may have loose engine mount bolts, or loose fuel tank mounts and worn out rubber dampers between tank and frame.

[olddogs]

A lot of bikes used a piece of foam rubber folded over the backbone under the tank. This caught some of the engine noise and muffled some of the vibration in the tanks tunnel area, keeping it from acting like a megaphone.

[relic]

Jack, good call on the tank and engine mounts; I built the bike over the winter and hadn't yet retorqued frame fasteners. But they are all tight.
Olddoogs, thanks; I do have a small piece of foam in the tank tunnel (to protect the frame paint during installation) but next time its off I'll see about adding some the full length of the tunnel. Regardless of this particular noise as you say it will muffle all the sound.
Turns out my dampers seemed to have worked. The noise I was hearing is gone. I had just rough cut some chunks of rubber to try so now I'll trim them uniform and put them in place.

Ken