Rocky Mountain Dirt Riders

Hi everyone,

I recently installed a new FMF Powercore 4 muffler (with S/A) onto the stock header of my 2005 CRF250r and did a quick db test with a cheapo sound meter.

According to my readings at idle, the sound was at 95-97db, I am wanting some input from anyone with a similar pipe with spark arrestor installed to see if you have similar db readings on your bikes. The readings were taken at apporx. 45 degrees outside angle at muffler outlet height.

I have been reading how loud the powercore pipe is and am surprised to find a decent sound reading, but again, my sound meter is not a $1000 model, and I have not calibrated it ever.

Thanks for any input!

The CMRC has adopted the FIM 2 metre max sound testing standard, so if you are planning on racing you should test to it as well. You can google search for a detailed procedure. I have never seen a $1000 sound tester at any event let alone properly trained sound testing personnel. I have been asked to take on the task of sound testing at this years off-road events as best as I can. I am planning on doing sound testing at our spring test and tune session at blackfoot MX park if you would like a second opinion.

Thanks Brenan225

I think I'm still going to order the quiet insert-
and take you up on the opportunity to have you sound test during the test and tune.

Depending on time, I may do some XC races this year plus I just want to be quiet when riding the public tracks.

I used the quiet insert on a powercore 4, albeit on a 450. I passed all the sound tests last year, and did ot notice any decrease in power that a extra bit of throttle couldn't fix. Spend the time getting your jetting dialed though...

AJRJ wrote:I used the quiet insert on a powercore 4, albeit on a 450. I passed all the sound tests last year, and did ot notice any decrease in power that a extra bit of throttle couldn't fix. Spend the time getting your jetting dialed though...

Thank you, that makes me feel a bit better about passing the noise tests.

Did you find your final jetting was more towards the richer or leaner side of stock setting?
I guess I automatically think an aftemarket muffler will really lean out the motor.

Check out the RMDRA Race web page. Link above to the right.

It has the complete sound testing methodology outlined.

The CRF250R has be reving at 5500rpm when the sound level is measured.

PaulS wrote:Did you find your final jetting was more towards the richer or leaner side of stock setting?
I guess I automatically think an aftemarket muffler will really lean out the motor.

I just ended up following the JD Jetting suggestions, and was very happy with how the bike ran. This was after some trial and error with the GYTR smog delete kit though. IMHO the JD kit was money well spent.

I used a PC4 with quiet insert on a YZ250F and had to lean out the main and needle a lot to get it to run correctly.

The JD kit worked great for me with the YZ muffler, however it didn't work at all once I put the quiet insert in it.

dirtyboy wrote:I used a PC4 with quiet insert on a YZ250F and had to lean out the main and needle a lot to get it to run correctly.

The JD kit worked great for me with the YZ muffler, however it didn't work at all once I put the quiet insert in it.

Thanks for all the great tips, it's truly appreciated.

I've got stock jetting right now.
With all your advice, I know that some jetting may be necessary but I will get a good base reading on the plug first.