Taking Your BMW C650 to a New Level “Of Sound” - Mike Mas

Low On Cash

New member
Taking Your BMW C650 to a New Level “Of Sound” - Mike Mas

As I think back to my first ride on my 650 Sport - I was totally impressed her ability to jump off the line. I’m not saying the 650 is a super bike or fast, however for a CVT drive system, this bike has terrific performance for just a 647cc engine. Regretfully, I also found the overall noise level in the 650’s cockpit to be un-acceptable. Most of the noise heard (general engine and internal chain noise) are attributed to its somewhat high rpm at low speeds. BMW designed their CVT to allow the engine to run up at speeds of 3000-4000 rpm, right from the minute you hit the throttle to keep engine ahead of its load. This is why the Sport and GT models have a great 0-60 mph speed. The downside of this design is when your tooling around town or stuck in slow moving traffic, unlike a geared bike running just above idle, the 650 ’s engine is turning around 4K even at speeds of 5-10 mph making noise and wasting fuel. Making matter worse, BMW’s latest CVT has an inherit high pitch whine which is also audible.



With this problem in Hand - My first modification would be insulating the body panels around the engine and transmission to reduce the noise level to include reducing the gear whine from the CVT.

In order to locate the Noise - I used my iPhone riding at 35 mph, to record different areas in the cockpit to find out exactly where most the noise was concentrated. Unlike some conventional scoots, which have the engine under the seat for quiet operation, the 650’s engine crankcase sits under the rider, however the cylinder heads are located in the tunnel only separated by a micro-thin panel transferring ton’s of noise. These thin flat panels, in turn become a virtual loud speaker to transfer and amplify the engine noise. Making it worse, the floor panel is directly facing the rider.



Installing the sound Insulation - The product I used to cure my noise problem is called; Stinger’s “RoadKill” this is a rubber type composite mat which is very sticky on one side and foil-backed on another. This product is a butyl rubber material with a .080 inch thickness, aside from stopping noise, it also kills vibration as well. The Polaris Slingshot has possibly the worst rear drive made, its so loud at times you can’t talk. I used this same RoadKill for my Sling making an inclosure around the gearbox and it made the noise manageable, so I figured it would be an easy task for the my BMW Sport.



After studying a parts listing to see how the center panel would be removed - I began by removing two screws on the ignition panel, then by turning the key body a few degrees, I could remove the center panel to gain access to two screws that hold the front of the tunnel cover. Make sure you use blue tape to protect your adjacent panels and paint from scratches.







Once I had the center panel removed - I had full access to the two side panels as well. Rather than remove the side panels, I used the outside as template then pre-cut pieces of insulation. I peeled back one end then stuck them in place inside the panels.

Since most of the noise was coming from the cylinder head area, I made a sort of firewall as shown in the image, which sealed that area to keep the noise from traveling upward to the rider. To make it even quieter, I also applied the insulation to the tunnel panel like I did the sidewalls.





To also help quiet the engine and high pitch whine from the CVT - I removed both the upper and lower panels on both sides of the 650 then cut and and applied the insulation to these panels as well.












Once I buttoned her back Up - I was ready for my first test drive to see how much difference it made. As soon as I started the engine, for the first time ever, the exhaust sound was louder than the noise and I could actually hear the note of the exhaust rather than the engine noise. As I rode down my driveway and got on the main road, it was almost like I was on a different bike. I found that being much quieter seemed to make the bike smoother as well. As a bonus, the annoying CVT whine was reduced to a point it does not even bother me any longer. I might mention that during my noise testing, I also found there was some noise amplified by the flat dash board panel. When I get some time, I’ll pull the two front side panels and install some insulation there as well to help absorb some of the noise that escapes forward to under the dash.

In conclusion - I’m happy with the results, it was time consuming but it made my beautiful 650 Sport that much more enjoyable.

Ride Safe - Mike


 
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SteveADV

Active member
Super excellent, Mike! I wonder how many parts I would have left over if I tried that?!? :D. But it sure sounds like it's worth the effort.
 

exavid

Member
Very impressive presentation. I've been annoyed by the mechanical noise of my GT too. I wonder what that insulation does to the temperature inside the fairing.
 

dukdukman

New member
Great improvement. Seriously consider doing the same. One thing makes me wonder: did you consider the heat reflected from the silver cover back onto the drivetrain? Would a non-silver surface possibly prevent this? Much interested in your thoughts.
 

Low On Cash

New member
Great improvement. Seriously consider doing the same. One thing makes me wonder: did you consider the heat reflected from the silver cover back onto the drivetrain? Would a non-silver surface possibly prevent this? Much interested in your thoughts.

Actually you'll want, to reflect both heat and noise away from the Road Kill and body panels. This also helps shield electronics and wires located in the panels from heat.

For the most part, any reflected heat from the engine is not a consideration since the water cooling in the block maintains a relative safe temperature, in addition there is air passing around the engine and these panels to help dissipate heat. The foil also serves another function which is to protect the insulation rubber from heat and weather elements to maintain its life.

This Road Kill is bullet proof, I have actually used it in fender wells and under the floorboards exposed to weather and rocks to deaden noise in my cars.

Mike
 

DPaul

New member
Very nice. What year model is your Sport?
The late models appear to have acoustic foam already applied.
So, not sure if this would work for the newer models.
 
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