Where to find db info on stock bikes

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#1
One of the dirt bike mags did a shootout recently between the 250X, XCF-W 250 and WR250F, which included db levels and weight. Honda was quietest, followed by Yamaha and trailing way back was KTM. Where can I find out this info for others bikes (KLX300 comes to mind for starters). The manufacturers sites only list the weight, not db levels. Thanks.
 

Tony Eeds

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#2
Interesting question.

You are to be commended for caring enough to ask.

I'm going to have to do some research on this.

I will be back ... soon.
 

RM_guy

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#3
That is a good question. I was always under the impression that generally speaking, KTM's were quieter. The other manufactures may say they are quiet but they are also choking the power to get there. The new WR450 is a good example with the throttle stop and a plugged up exhaust to make it quiet.

On a side note...are you interested in a trial ride in Hancock, NY this weekend? It's not far from you. Here's a link to the post on it. http://dirtrider.net/forums3/showthread.php?t=150088
 

dirt bike dave

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#4
Unless you know the bikes were compared using the same method and equipment, I would be careful in comparing data obtained online.

Different meters using different scales or placed at different angles or different distances from the exhaust will make a big difference in measured dB.

Basically, there are a lot of variables and someone's measured 98 db might be quieter than someone elses measured 96 db.

The magazine test cited above was probably consistent in their methods, but I doubt you can compare their results to random tests of other bikes.
 
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#5
On a side note...are you interested in a trial ride in Hancock, NY this weekend? It's not far from you. Here's a link to the post on it. http://dirtrider.net/forums3/showthread.php?t=150088
Thanks for the info, but there's something wrong with my bike today so I'm taking it into the shop tomorrow and I doubt I'll get it back by the w/e. Figures it craps out just when the weather breaks. Have fun on the ride!! :ride:
 

Tony Eeds

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#6
dirt bike dave said:
Unless you know the bikes were compared using the same method and equipment, I would be careful in comparing data obtained online.

Different meters using different scales or placed at different angles or different distances from the exhaust will make a big difference in measured dB.

Basically, there are a lot of variables and someone's measured 98 db might be quieter than someone elses measured 96 db.

The magazine test cited above was probably consistent in their methods, but I doubt you can compare their results to random tests of other bikes.
Dave: There are VERY specific rules and criteria that must be followed to accurately determine the dB rating of a bike.

It is not accurate to say that a bike measuring 98 dB would be quieter than a bike measuring 96 dB, unless the testing procedures are not followed.

To test a bike the sound meter must be 20 inches and 45 degrees from the exhaust tip and the RPM at 50% of the RPM at max horsepower ... or torque ... I've forgotten which at the moment.

Check out the RPM chart here to learn about your particular bike. Chris Real and his partner are heavily involved in the sound issues. His partner (who's name escapes me at the moment) wrote the rules (SAE J1287) that we follow when determining the noise generated by a motorcycle in a static situation. This is the source of the 96 dB requirement that many people reference.

Here is a link to their motorcycle sound website.

You are accurate in saying that the tests cannot likely be duplicated over a long period of time on the same machine, but the reason is related to the type of exhaust system. Generally speaking, after market exhaust systems rely on packing that deteriorates over time and a machine with maybe 20 hours of time on the packing will not match it's own results with fresh packing.

Indeed, 20 hours of run time can easily be the difference between legal and illegal.

If you get stopped for sound measurement by a ranger and he issues you a citation, be sure and collect the data related to the sound meter used, the method and the range the meter was set on. Also follow up and ask for the most recent calibration info on the unit when you get home. Not every unit made is usable for law enforcement. It must be a Type 1 meter, to be admissible in court.

Sound is a HUGE issue and, by far, the most talked about subject at the recent NOHVCC conference.

Please keep your machines at or below the 96 dB rating. I am leaving the stock exhaust on my DR650, as it is well capable of scaring me in the stock configuration.

There is zero connection between the level of sound that a machine makes and the horsepower output.

As a final thought ... if loud pipes save lives, why don't pipes face forward.
 

DieselTech

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#7
Yes, I too would like quieter exhaust - so my neighbors won't be bothered! I'd love to get my MX bikes close to the sound of a stock XR-series bike (or a dual-purpose machine, as they are rather quiet also), but there seems to be no aftermarket solution to the noise issue that really quiets the bikes down (esp. the 4t's). If ANYONE has any experience with any products that work well, I'm all ears.............
 

Tony Eeds

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#8
DieselTech said:
Yes, I too would like quieter exhaust - so my neighbors won't be bothered! I'd love to get my MX bikes close to the sound of a stock XR-series bike (or a dual-purpose machine, as they are rather quiet also), but there seems to be no aftermarket solution to the noise issue that really quiets the bikes down (esp. the 4t's). If ANYONE has any experience with any products that work well, I'm all ears.............
DT:

This is, at best, an ongoing evolution (revolution?).

Do you have a preferred can supplier that you like? Bug them about quieter exhaust.

FMF has stepped forward to address the issue and developed the Q and the Q2.

I have a Q on my XR650R and liked it at first. I'm fairly certain it exceeds the 96 dB level at this point, but do not personally have a sound meter to measure it with.

My reference in the post above was a story about a CRF450 that "complied" when new, but blew 100 dB after 20 hours of track time. 100 dB is a huge jump from 96 dB, because it is a logarithmic scale.

I asked about the 150s that I have heard about as being loud. Cris indicated that it is exhaust speed as much as anything. There is just very little pipe to work with.

The AMA is finally addressing the issue for closed course competition, so this will push the pipe manufacturers even harder. It is a phased change though, so expect it to take a few years.
 
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#11
Shootouts in the dirtbike magazines are very popular, and I forgot to commend the mags for including the db info when they did the shootout - hopefully they'll continue to do so.

And thanks for all the posted info and links! :cool: