Attempting to alleviate engine noise/ skid plate noise R&D

Ever since about the second day of owning my 2008 wrr I had always secretly wished the motor ran a little quieter. I personally find the noise irritating and unrefined. The noise comes from the unique valve train design, though I want to say my yz400f was a little smoother sounding.

Since the noise "should" be mostly valve train related, I had myself the grand idea the other day while responding to the recent skid plate thread. Why not insulate(bed liner) the valve cover? This same idea has been explored somewhat on multiple diesel forums with varied results.

Soo I did, I used two cans of spray can bedliner (both rustoleum and duplicolor). I am just waiting on the relatively "thick" application to cure. I also fully anticipate having to remove this product if it can't cope with the heat.

https://wr250rforum.forumotion.com/t7721-flatlands-raceing-skid-plate-noise

primer:



sprayed:look at that beautiful finish!  



Also I believe a plastic tank especially the larger safari style tanks will have an effect on perceived noise.

I also plan on developing some sort of engine mat/blanket that will go between the valve cover and the gas tank. This blanket piece may incorporate some sort of rock wool, foam, tin foil, rubber sandwich. That will reflect and absorb sounds.

P.S. I realize a lot of people will shake their heads at this but it gives me something to do, and i do believe there are measurable results to be had. I encourage people to respond and offer any ideas as well as vote on the poll. Ohh this bike has a salvage title so the resale isn't a big concern.

I can not lie, it does look funny, will be interested if it works, cheers

Great feedback so far! The poll right now seems to be inferring a relationship between the stock metal tank and noise transmission to the rider. If this is the case I hope to at least mimic this by making it harder for the sound to reach the rider.

I would love for anyone with a plastic tank to post an outdoor at idle decibel reading with a basic phone app. I also welcome those that don't notice excessive noise to compare readings. I believe my base line reading with phone at head level was around 82 db.

Thanks for commenting fiftgrit! yes, the finish looks pretty awful especially from above, the sides are slightly better lol.

I started with the rustoleum since reviews sounded like it stuck better without peeling, It was also a much thinner product so I had to do very thin coats or it acted like it wanted to run. I applied the duplicolor the same way but it must have been much much thicker causing it to build up almost like snow.

The liner is just about dried out and will probably be put back on tonight, but right now I am exposing it to a little heat to see how it copes and get it acquainted with engine temperatures. I have had it in the toaster oven over night at 100 degrees. I am slowly creeping it up towards 180 degrees so far so good.

Sorry about the pics guys, I did not realize i had taken them sideways   . I am not yet ready to post any results just yet. Though the bed liner appears to be fully cured, it has become a lot harder than I thought it would and acts like its up for the job.

For as much as one really sees it I think it looks great, and after curing the texture is not as extreme as it initially was.

P.S. checkout the slick new home for my horn (see 1st pic)

necessity is the mother of invention.. so hammer down problems any way you see fit .Be interesting to see the before and after db readings.

I went to Ace hardware yesterday and bought a big piece of rubber, enough to attach to the back of my skid plate plus some, while I was there I noticed they sell this cool thermal insulation type stuff by the foot as well.

The noise blanket/barrier consists of pieces of rubber on either side of the thermal sheet. The thermal sheet completely seals the engine compartment and at the very least should keep the gas tank a little cooler, by keeping it insulated while also reflecting both heat and hopefully noise while the rubber in theory is very dense and will absorb noises.

Well I've gotten the chance to ride it now with all the modifications completed. Its hard to remain objective but my initial impression is that the engine sounds smoother and the noise level is reduced to about like having the skid plate removed.

I still need to do a db reading with the phone and take a properly long ride where I'm am more inclined to get annoyed by things but around town seems to be improved.

I think the rubber backing looks nice just need to glue it down on the wings:

good that your seeing some improvement.  

..I've  noticed that forum members rarely suspect any noise issues due to helmet type or helmet fitment. In colder weather i wear a neck gator while bike riding.. it cuts the noise infiltrating the helmet by at least 1/3 due to the tight fit against the bottom of the noisey shoei hornet helmet i have. There are neck gators for warmer climate as well to curb bug hits on the neck.... not sure how tight they fit against the helmet though,,

haha thanks RPB, I want to do a db reading tomorrow, just scared that the exhaust being the loudest component will therefore render the test inconclusive. I know I have eliminated pretty much all the extra noise associated with having a skid plate on my bike, so I guess mission accomplished there.

That 1/8th inch of rubber makes a lot of difference and is probably the cheapest and easiest solution .

Very true I'm sure that helmet choice and hearing protection is probably the biggest thing you can do, for instance I can shrug while riding in certain positions and that reduces perceived sound a good deal. I have a medium arai and a large scorpion I will have to test that. I mainly wear the scorpion for the looks and comfort since the arai is pretty snug and is white. I like wearing ear plugs on longer rides but then I feel somewhat detached from the experience.

Took a measurement of the DB level and went for a pretty decent ride!

Here is a screen shot with phone held at head level while seated, motor fully warmed up:


The measurement was nearly identical to before, which was about 82db this to me looks like 81db or so.

As for my perception initial startup is quieter, then once fully warm idle sounds cleaner less chatter/maracas playing. Riding is a lot less fatiguing on my 40 mile round trip I felt comfortable at 50-60mph all the way up into the forest or about 20 miles, before I would have started feeling abusive/annoyed around 10-15 miles in.

Once I was up in the forest I ran into two other riders, an XR600 and an early 80's yamaha (yz?) 250. I immediately remembered how quiet my bike is as I could only hear their engines. We all ended up hanging out and talking for a bit after the 600 rider stalled and couldn't restart from the carb flooding.

The YZ rider and me ended up doing 3 very close drag races standing starts on gravel, I won 2 of the 3. He let me ride his bike before hand and it actually was a lot lighter and had more pull but had a very short power band, so I wasn't sure how the race would turn out. Luckily the wr has a short 1st gear and I had a little better clutch control, once I was in 4th he would start to catch up but there was not enough road and we were going at least 65 by then. BTW he was claiming his bike was 33hp based on his own research.