FMF Powercore 4 quiet insert ...mod...

Any comments would be appreciated...

The fella at the dealer bought a new FMF muffler for his RMZ.He just races it so has no use for the quiet insert.
It resembles the pc4 factory insert....except the pc4 has a stainless steel flange on the end...where this is an aluminum ring insert (thick), with an o-ring groove near the outer edge....an O-ring!?!
It's about a .120" dia. too large for my pc4.

Assuming a reasonable price, I could get it turned down to my diameter.

I've held it in place...it almost goes.

Not sure what kinda o-ring they use...but a wider groove may compensate for that one being a little large.

I'm not sure his exact bike or muffler at the moment...I'll remember to ask next time.

Any good reason not to try?

1/8" is quite a bit to turn off, well can be, depending on the wall thickness of the pipe that will be left. You would have to measure the ID/OD and compare it to the ID of your pipe. If you turn it down and are only left with a wall thickness of .02/.03" then it may just be a waist of time. If you are left with a wall thinkness of .1"+ then there is no reason it shouldn't work.

Does the price for a proper quiet insert versus buying one and pissin around to make one fit worth it??? That would be my question. As a machinist, I know I could do the work for free, but if you have to pay someone it may not be worth the time/money.

If this is the one, there is no room to turn it down by 1/8". Won't be anything left

http://www.motosport.com/dirtbike/FMF-POWERCORE-QUIET-CORE-INSERT

That looks like the proper (flanged) one, in your link
The one I could get has a solid aluminum ring id 1 1/4", od 1 7/8"...pressed onto the stainless tube...so alot of meat there. No flange, just insert, completely, in the hole and the o-ring seals it.
I could probably get it turned for $20 or less...would only take a minute. Plus the o-ring groove should be tweaked too.
If I could get it for $20= fix for 20...40 would sound cheaper than ordering one...not to mention a month or so wait to order the proper one.

http://www.fmfracing.com/Products/MX/599

The proper one looks like the far right....the one I can get, looks like the third from the right.
The tube and spark arresstor style looks almost identical for both.

Well, I turned it down to 1.650", put a new o-ring...and it slipped right in and sealed up pretty well....coulda been a couple thou larger, but not bad.
Had to rat tail file the little screw hole a bit, so it could set in as far as possible...just barely hiding the o-ring.
But a good fit overall.
Keep in mind I just repacked my muffler with general fmf packing...
...and it is definitely the quietest it has ever been.
I am definitely pleased with the sound level difference...Though not extreme...the tone has lost that higher pitched buzz at wot, while pleasantly quieter/bassier at low revs as well.
Mostly lower revs, but better everywhere really.

I've only had one ride...the sensation was the bike didnt rev as quickly as before, but not much.
Lost a little scream maybe, but I'll know better as I ride it.
Worked better than I hoped so far...sounds better to me.
Might make the difference between earplugs or not for me...I like that.

Nothing like the DB dog I tried, where I wasnt sure if there was a difference...this time there was a difference.
The new bag o packing surely helps too...