Posts
2181
Joined
7/25/2009
Location
Somewhere in, NJ, USA
Edited Date/Time
5/8/2014 5:10pm
Yoshimura has several inserts for their RS-4 exhaust system that are not so easy to figure out on paper or after a tech call to Yosh.
My 2012 CRf450 ran good with the FMF RCT 4.1 exhaust that replaced the tiny outlet of the stock exhaust. The outlet of the FMF muffler was about 1.67".. much bigger than the 1.05" stock outlet.
I then tried a full titanium and carbon fiber Yoshimura system which comes with their "AMA Sound Insert" which is 94 db. i was surprised by the tiny outlet the Yosh muffler came with. It measured only 1.24" in diameter!
I had a very confusing call with Yosh tech. i dont like loud but I asked them which insert would give the best power. He suggested the 2M Max insert. I asked him how many dB it was rated at and he said 110 dB. I naturally figured that the diameter of the opening of the 110 dB insert must be bigger than the 96 and 99 dB inserts so I asked him the diameter of the inserts and said they are all 1.5" which is written on the packing label. This made no f'in sense whatsoever so i ended the call and ordered every insert they sold to figure it out myself as there is no explanation anywhere about their insert system and it is not intuitive.
None of the inserts are 1.5" in diameter.. they are all less than that and all much smaller then the FMF. 1.5" must be the size of the muffler opening and not the nsert so refering to it is totally useless. The 99 dB insert measured 1.42" in diameter.. still no where near the size of the FMF outlet. If the 2M max insert is rated at 110 dB, I expected it to be bigger in diameter.. nope, it was the exact same 1.42" in diameter as the 99 dB insert except it had a piece of perforated steel welded over the end of it which makes it at least a but more restrictive than the 99 dB insert so how the heck could it be rated at 110 dB. The only answer to that is that the 2M max insert is rated in a different way than all the other inserts they sell and actually would be quieter than the 99 dB insert if measured the same way. You would never figure this out from the info they provide.
End of story.. if you want the least restrictive insert, go with the 99 dB insert which is what I did and dont bother asking Yosh or looking for an explantion in their literature as you won't find it.
Stock 2012 CRF450 - 1.05"
Yosh "AMA Sound" insert - 1.24" (94 d
Yosh "2M Max" insert - 1.42" + perforated screen on the end (I am guessing around 96 d
Yosh "99 dB" Insert - 1.42" (99 d
FMF RCT 4.1 - 1.67" (the loudest of all but from the rider's seat not that much noticable over the Yosh 99 dB insert)
The Yosh with the AMA sound or 99 dB inserts will defintely gave the bike more lower end power than the FMFbut not as much on top and not as smooth a transition from bottom to mid. The Yosh full carbon fiber and titanium muffler looks great ,but beware, it is pig heavy for the materials used.. it is .84 lbs heavier than the FMFaluminum and steel muffler and 1.58 lbs heavier than the FMF titanium RCT muffler!
Anyone running without the insert at all? This would bring the Yosh outlet diameter closer in size to the FMF RCT 4.1 muffler.
mike
My 2012 CRf450 ran good with the FMF RCT 4.1 exhaust that replaced the tiny outlet of the stock exhaust. The outlet of the FMF muffler was about 1.67".. much bigger than the 1.05" stock outlet.
I then tried a full titanium and carbon fiber Yoshimura system which comes with their "AMA Sound Insert" which is 94 db. i was surprised by the tiny outlet the Yosh muffler came with. It measured only 1.24" in diameter!
I had a very confusing call with Yosh tech. i dont like loud but I asked them which insert would give the best power. He suggested the 2M Max insert. I asked him how many dB it was rated at and he said 110 dB. I naturally figured that the diameter of the opening of the 110 dB insert must be bigger than the 96 and 99 dB inserts so I asked him the diameter of the inserts and said they are all 1.5" which is written on the packing label. This made no f'in sense whatsoever so i ended the call and ordered every insert they sold to figure it out myself as there is no explanation anywhere about their insert system and it is not intuitive.
None of the inserts are 1.5" in diameter.. they are all less than that and all much smaller then the FMF. 1.5" must be the size of the muffler opening and not the nsert so refering to it is totally useless. The 99 dB insert measured 1.42" in diameter.. still no where near the size of the FMF outlet. If the 2M max insert is rated at 110 dB, I expected it to be bigger in diameter.. nope, it was the exact same 1.42" in diameter as the 99 dB insert except it had a piece of perforated steel welded over the end of it which makes it at least a but more restrictive than the 99 dB insert so how the heck could it be rated at 110 dB. The only answer to that is that the 2M max insert is rated in a different way than all the other inserts they sell and actually would be quieter than the 99 dB insert if measured the same way. You would never figure this out from the info they provide.
End of story.. if you want the least restrictive insert, go with the 99 dB insert which is what I did and dont bother asking Yosh or looking for an explantion in their literature as you won't find it.
Stock 2012 CRF450 - 1.05"
Yosh "AMA Sound" insert - 1.24" (94 d
Yosh "2M Max" insert - 1.42" + perforated screen on the end (I am guessing around 96 d
Yosh "99 dB" Insert - 1.42" (99 d
FMF RCT 4.1 - 1.67" (the loudest of all but from the rider's seat not that much noticable over the Yosh 99 dB insert)
The Yosh with the AMA sound or 99 dB inserts will defintely gave the bike more lower end power than the FMFbut not as much on top and not as smooth a transition from bottom to mid. The Yosh full carbon fiber and titanium muffler looks great ,but beware, it is pig heavy for the materials used.. it is .84 lbs heavier than the FMFaluminum and steel muffler and 1.58 lbs heavier than the FMF titanium RCT muffler!
Anyone running without the insert at all? This would bring the Yosh outlet diameter closer in size to the FMF RCT 4.1 muffler.
mike
mike
"Unfortunately I don’t show that we have a 99dB insert available. I see a 94dB and a 2m-Max insert. Typically the 2m-Max insert is the best performing, so if you don’t have sound requirements where you ride then I would get that one. The insert is not spark arrested though. Here is the part number and price for that item:
INS-14-K $29.95 MSRP"
mike
The Shop
DeCal Works Huge Plastic Inventory of UFO and Polisport kits.
Luxon 4-Post Bar Mounts
$189.95 - $239.95
I put the link to dennis kirk above because when i go to purchase that part number from dennis kirk its telling me that its a 94 db insert which is the one i already have.
"Low-Volume Insert (94 dB ) for RS-4 (INS-14-K) Muffler Type - INS14K Part #: 435561" .. the 94 dB info stated is wrong!.. this is the 99 dB insert.
Both look great imo though
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